@article{pauly_white_deegbey_fosu_keller_mcguigan_dianat_gabilondo_wong_murphey_et al._2024, title={Coordination of copper within a crystalline carbon nitride and its catalytic reduction of CO<sub>2</sub>}, volume={3}, ISSN={["1477-9234"]}, DOI={10.1039/d4dt00359d}, abstractNote={Inherently disordered structures of carbon nitrides have hindered an atomic level tunability and understanding of their catalytic reactivity. Starting from a crystalline carbon nitride, poly(triazine imide) or PTI/LiCl, the coordination of copper cations to its intralayer N-triazine groups was investigated using molten salt reactions. The reaction of PTI/LiCl within CuCl or eutectic KCl/CuCl2 molten salt mixtures at 280 to 450 °C could be used to yield three partially disordered and ordered structures, wherein the Cu cations are found to coordinate within the intralayer cavities. Local structural differences and the copper content, i.e., whether full or partial occupancy of the intralayer cavity occurs, were found to be dependent on the reaction temperature and Cu-containing salt. Crystallites of Cu-coordinated PTI were also found to electrophoretically deposit from aqueous particle suspensions onto either graphite or FTO electrodes. As a result, electrocatalytic current densities for the reduction of CO2 and H2O reached as high as ∼10 to 50 mA cm-2, and remained stable for >2 days. Selectivity for the reduction of CO2 to CO vs. H2 increases for thinner crystals as well as for when two Cu cations coordinate within the intralayer cavities of PTI. Mechanistic calculations have also revealed the electrocatalytic activity for CO2 reduction requires a smaller thermodynamic driving force with two neighboring Cu atoms per cavity as compared to a single Cu atom. These results thus establish a useful synthetic pathway to metal-coordination in a crystalline carbon nitride and show great potential for mediating stable CO2 reduction at sizable current densities.}, journal={DALTON TRANSACTIONS}, author={Pauly, Magnus and White, Ethan and Deegbey, Mawuli and Fosu, Emmanuel Adu and Keller, Landon and Mcguigan, Scott and Dianat, Golnaz and Gabilondo, Eric and Wong, Jian Cheng and Murphey, Corban G. E. and et al.}, year={2024}, month={Mar} }
 @article{jana_gabilondo_mcguigan_maggard_2024, title={Syntheses, Crystal Structures, and Electronic Structures of Quaternary Group IV-Selenide Semiconductors}, volume={3}, ISSN={["1520-510X"]}, DOI={10.1021/acs.inorgchem.4c00363}, abstractNote={Early transition-metal chalcogenides have garnered recent attention for their optoelectronic properties for solar energy conversion. Herein, the first Zr-/Hf-chalcogenides with a main group cation, Ba9Hf3Sn2Se19 (1) and Ba8Zr2SnSe13(Se2) (2), have been synthesized. The structure of 1 is formed from isolated SnSe44- tetrahedra and distorted HfSe6 octahedra. The latter condense via face-sharing trimeric motifs that are further vertex-bridged into chains of 1∞[Hf(1)2Hf(2)Se11]10-. The structure of 2 is comprised of SnSe44- tetrahedra, Se22- dimers, and face-sharing dimers of distorted ZrSe6 octahedra. These represent the first reported examples of Hf-/Zr-chalcogenides exhibiting face-sharing octahedra with relatively short Hf-Hf and Zr-Zr distances. Their preparation in high purity is inhibited by their low thermodynamic stability, with calculations showing small calculated ΔUdec values of +7 and +9 meV atom-1 for 1 and 2, respectively. Diffuse reflectance measurements confirm the semiconducting nature of 1 with an indirect band gap of ∼1.4(1) eV. Electronic structure calculations show that the band gap absorptions arise from transitions between predominantly Se-4p valence bands and mixed Hf-5d/Sn-5p or Zr-4d/Sn-5p conduction bands. Optical absorption coefficients were calculated to be more than ∼105 cm-1 at greater than 1.8 eV. Thus, promising optical properties are demonstrated for solar energy conversion within these synthetically challenging chemical systems.}, journal={INORGANIC CHEMISTRY}, author={Jana, Subhendu and Gabilondo, Eric and McGuigan, Scott and Maggard, Paul A.}, year={2024}, month={Mar} }
 @article{jana_gabilondo_maggard_2024, title={Two new multinary chalcogenides with (Se<sub>2</sub>)<SUP>2-</SUP> dimers: Ba<sub>8</sub>Hf<sub>2</sub>Se<sub>11</sub>(Se<sub>2</sub>) and Ba<sub>9</sub>Hf<sub>3</sub>Se<sub>14</sub>(Se<sub>2</sub>)}, volume={329}, ISSN={["1095-726X"]}, DOI={10.1016/j.jssc.2023.124376}, abstractNote={Two multinary selenides, Ba8Hf2Se11(Se2) and Ba9Hf3Se14(Se2), with unprecedented structure types have been prepared using high-temperature synthesis techniques and represent the first known compounds in the Ba-Hf-Se system. Their structures were determined from single crystal X-ray diffraction (XRD) data. The Ba8Hf2Se11(Se2) compound crystallizes in the monoclinic C2/c space group with a = 12.3962(15) Å, b = 12.8928(15) Å, c = 18.1768(17) Å, and β = 90.685(4)º, while Ba9Hf3Se14(Se2) forms in the rhombohedral R 3¯ space group with a = b = 19.4907(6) Å and c = 23.6407(11) Å. Both have pseudo-zero-dimensional structures with homoatomic Se–Se bonding in the form of (Se2)2− at distances of 2.400–2.402 Å. The structure of Ba8Hf2Se11(Se2) is comprised of [Hf2Se11]14−, Ba2+, and (Se2)2− dimers. Conversely, the Ba9Hf3Se14(Se2) structure contains a novel perovskite-type cluster constructed from eight octahedrally-coordinated Hf cations, i.e., [Hf8Se36]40−, and isolated [HfSe6]8− units which are separated by (Se2)2− dimers and Ba2+ cations. Polycrystalline Ba8Hf2Se11(Se2) is synthesized at 1073 K using a two-step solid-state synthesis method, with the co-formation of a small amount of BaSe secondary phase. A direct bandgap of 2.2(2) eV is obtained for the polycrystalline sample of Ba8Hf2Se11(Se2), which is consistent with its yellow color. Density functional theory calculations reveal their bandgap transitions stem from predominantly filled Se-4p to empty Hf-5d at the edges of the valence bands (VB) and conduction bands (CB), respectively. The optical absorption coefficients are calculated to be large, exceeding ∼105 cm−1 at about >2.0 eV with effective masses in the CB varying from ∼0.5 me (Γ → A) in Ba8Hf2Se11(Se2) to ∼1.0 me (Γ → L) in Ba9Hf3Se14(Se2). Thus, their optoelectronic properties are shown to be competitive with existing perovskite-type chalcogenides that have been a focus of recent research efforts.}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Jana, Subhendu and Gabilondo, Eric A. and Maggard, Paul A.}, year={2024}, month={Jan} }
 @article{o'donnell_gabilondo_jana_koldemir_block_whangbo_kremer_pottgen_maggard_2023, title={Cation exchange route to a Eu(II)-containing tantalum oxide}, volume={328}, ISSN={["1095-726X"]}, DOI={10.1016/j.jssc.2023.124338}, abstractNote={Traditional synthetic efforts to prepare Eu(II)-containing oxides have principally involved the use of high temperature reactions starting from EuO or a controlled, highly-reducing, atmosphere. Conversely, chimie douce approaches that are more amenable to the targeted syntheses of new, and potentially metastable, Eu(II)-oxides have yet to be explored. Herein, a cation-exchange route to new Eu(II)-containing oxides, e.g., EuTa4-xO11 (x = 0.04), has been discovered and its structure determined by powder X-ray diffraction (Space group P6322 (#182), a = 6.2539(2) Å; c = 12.3417(2) Å). The compound derives from the cation exchange of Na2Ta4O11, via a reaction with EuBr2 at 1173 K, and replacement by half the number of divalent Eu cations. Rietveld refinements show preferential ordering of the Eu cations over one of the two possible cation sites, i.e., Wyckoff site 2d (∼94%; Eu1) versus 2b (∼6%; Eu2). Total energy calculations confirm an energetic preference of the Eu cation in the 2d site. Tantalum vacancies of ∼1% occur within the layer of Eu cations and TaO6 octahedra, and ∼20% partial oxidation of Eu(II) to Eu(III) cations from charge balance considerations. 151Eu Mössbauer spectroscopy measured at 78 K found a Eu(II):Eu(III) ratio of 69:31, with a relatively broad line width of the former signal of Γ = 7.6(2) mm s–1. Also, the temperature-dependent magnetic susceptibility could be fitted to a Curie Weiss expression, giving a μeff = 6.2 μB and θCW = −10 K and confirming a mixture of Eu(II)/Eu(III) cations. The optical bandgap of EuTa4-xO11 was found to be ∼1.5 eV (indirect), significantly redshifted as compared to ∼4.1 eV for Na2Ta4O11. Spin-polarized electronic structure calculations show that this redshift stems from the addition of Eu 4f7 states as a higher-energy valence band. Thus, these results demonstrate a new cation-exchange approach that represents a useful synthetic pathway to new Eu(II)-containing oxides for tunable magnetic and optical properties.}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={O'Donnell, Shaun and Gabilondo, Eric and Jana, Subhendu and Koldemir, Aylin and Block, Theresa and Whangbo, Myung-Hwan and Kremer, Reinhard and Pottgen, Rainer and Maggard, Paul A.}, year={2023}, month={Dec} }
 @article{mcguigan_tereniak_donley_smith_jeon_zhao_sampaio_pauly_keller_collins_et al._2023, title={Discovery of a Hybrid System for Photocatalytic CO<sub>2</sub> Reduction via Attachment of a Molecular Cobalt-Quaterpyridine Complex to a Crystalline Carbon Nitride}, volume={10}, ISSN={["2574-0962"]}, DOI={10.1021/acsaem.3c01670}, abstractNote={While recent reports have demonstrated the attachment of molecular catalysts to amorphous, graphitic carbon nitrides (g-CN) for light-driven CO2 reduction, approaches to the utilization of crystalline carbon nitrides have remained undiscovered. Herein, a functional hybrid photocatalyst system has been found using a crystalline carbon nitride semiconductor, poly(triazine imide) lithium chloride (PTI-LiCl), with a surface-attached CoCl2(qpy-Ph-COOH) catalyst for CO2 reduction. The molecular catalyst attaches to PTI-LiCl at concentrations from 0.10 to 4.30 wt % and exhibits ∼96% selectivity for CO production in a CO2-saturated, aqueous 0.5 M KHCO3 solution. Optimal loadings were found to be within 0.42–1.04 wt % with rates between 1,400 and 1,550 μmol CO/g·h at an irradiance of 172 mW/cm2 (λ = 390 nm) and apparent quantum yields of ∼2%. This optimized loading is postulated to represent a balance between maximal turnover frequency (TOF; 300+ h–1) and excess catalyst that can limit excited-electron lifetimes, as probed via transient absorption spectroscopy. An increase in the incident irradiance yields a concomitant increase in the TOFs and CO rates only for the higher catalyst loadings, reaching up to 2,149 μmol CO/g·h with a more efficient use of the catalyst surface capacity. The lower catalyst loadings, by comparison, already function at maximal TOFs. Higher surface loadings are also found to help mitigate deactivation of the molecular catalysts during extended catalytic testing (>24 h) owing to the greater net surface capacity for CO2 reduction, thus representing an effective strategy to extend lifetime. The hybrid particles can be deposited onto an FTO substrate to yield ∼60% Faradaic efficiency for photoelectrochemical CO production at −1.2 V vs Ag/AgCl bias. In summary, these results demonstrate the synergistic combination of a crystalline carbon nitride with a molecular catalyst that achieves among the highest known rates in carbon-nitride systems for the light-driven CO2 reduction to CO in aqueous solution with >95% selectivity.}, journal={ACS APPLIED ENERGY MATERIALS}, author={McGuigan, Scott and Tereniak, Stephen J. and Donley, Carrie L. and Smith, Avery and Jeon, Sungho and Zhao, Fengyi and Sampaio, Renato N. and Pauly, Magnus and Keller, Landon and Collins, Leonard and et al.}, year={2023}, month={Oct} }
 @article{cypher_pauly_castro_donley_maggard_goldberg_2023, title={Ethanol Upgrading to n-Butanol Using Transition-Metal-Incorporated Poly(triazine)imide Frameworks}, volume={15}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.3c07396}, abstractNote={The upgrading of ethanol to n-butanol was performed using a molecular catalyst integrated into a carbon nitride support, one of the first examples of a supported molecular catalyst performing the Guerbet process. Initial studies using crystalline poly(triazine)imide (PTI) with lithium or transition-metal cations imbedded in the support together with a base as the catalyst system did not produce any significant amounts of n-butanol. However, when using the catalyst material formed by treatment of PTI-LiCl with [(Cp*)IrCl2]2 (Cp* = pentamethylcyclopentadienyl) along with sodium hydroxide, a 59% selectivity for butanol (13% yield) was obtained at 145 °C. This PTI-(Cp*)Ir material exhibited distinct UV-vis absorption features and powder X-ray diffractions which differ from those of the parent PTI-LiCl and [(Cp*)IrCl2]2. The PTI-(Cp*)Ir material was found to have a metal loading of 27% iridium per empirical unit of the framework. Along with the formation of n-butanol from the Guerbet reaction, the presence of higher chain alcohols was also observed.}, number={30}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Cypher, Sabrine M. and Pauly, Magnus and Castro, Leslie G. and Donley, Carrie L. and Maggard, Paul A. and Goldberg, Karen I.}, year={2023}, month={Jul}, pages={36384–36393} }
 @article{o'donnell_kremer_maggard_2023, title={Metastability and Photoelectrochemical Properties of Cu2SnO3 and Cu2-XLiXTiO3: Two Cu(I)-Based Oxides with Delafossite Structures}, volume={1}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.2c03563}, abstractNote={Metastable, p-type Cu(I)-based semiconductors were synthesized using cation-exchange reactions between delafossite-type layered precursors and CuCl flux, yielding Cu2SnO3 (I) and Cu2–xLixTiO3 (II, xmin ∼ 0.4). These represent the first reported crystalline semiconductors found in the Cu–Sn–O or Cu–Ti–O chemical systems (and not currently predicted within any materials databases), with their kinetic stabilization requiring a relatively low reaction temperature of ∼475 °C. Both phases crystallize in the monoclinic crystal system in the space group C2/c, exhibiting edge-shared hexagonal “MO3” (M = Sn or Ti) layers that also contain octahedrally coordinated Li(I)/Cu(I) cations. These layers are bridged by linearly coordinated Cu(I) cations. Magnetic susceptibility measurements confirm the +1 oxidation state of the copper cations. The optical band gaps were found to be indirect and to significantly red shift with the Cu(I) content, down to ∼2.31 eV for I and ∼1.46 eV for II. Electronic structure calculations show that the decreased band gaps can be attributed to a higher energy valence band derived from the filled 3d10 orbitals of the Cu(I) cations, which most notably arise from the octahedrally coordinated Cu(I) cations within the layers. Total energy calculations reveal an increasing metastability with respect to decomposition to Cu2O and SnO2 or TiO2 as a result of occupation of the intralayer sites by Cu(I) cations. In both phases, their edge-shared hexagonal layers lead to highly dispersive conduction bands and small electron effective masses of ∼0.51 me for I and ∼0.41 me for II. Polycrystalline films of both were deposited onto fluorine-doped tin oxide slides and exhibited p-type photocurrents under 100 mW cm–2 irradiation in the range of ∼50 to 250 μA cm–2. This study thus reveals new fundamental relationships between the origin of metastability in Cu(I)-oxide semiconductors, i.e., octahedral coordination, and enhanced optical and photoelectrochemical properties.}, journal={CHEMISTRY OF MATERIALS}, author={O'Donnell, Shaun and Kremer, Reinhard K. and Maggard, Paul A.}, year={2023}, month={Jan}, pages={1404–1416} }
 @article{frick_sridhar_khansari_comstock_norman_o'donnell_maggard_sun_dougherty_2023, title={Spreading resistance effects in tunneling spectroscopy of α-RuCl3 and Ir0.5Ru0.5Cl3}, volume={108}, ISSN={["2469-9969"]}, url={https://doi.org/10.1103/PhysRevB.108.245410}, DOI={10.1103/PhysRevB.108.245410}, abstractNote={The Mott insulating state is the progenitor of many interesting quantum phases of matter including the famous high-temperature superconductors and quantum spin liquids. A recent candidate for novel spin liquid phenomena is $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$, a layered honeycomb Mott insulator whose electronic structure has been a source of mystery. In particular, scanning tunneling spectroscopy has indicated a Mott gap in $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$ that is much lower than the 2-eV value observed in photoemission measurements. Here, we show that the origin of this discrepancy is a spreading resistance artifact associated with tunneling into highly resistive materials by comparing with prior experiments and numerical modeling. A similar phenomenon is also observed in a substitutional alloy, ${\mathrm{Ir}}_{0.5}{\mathrm{Ru}}_{0.5}{\mathrm{Cl}}_{3}$, that has a higher resistivity than the parent compound. While the tunneling measurements cannot be used to accurately measure the sample density of states for these materials, we can take advantage of the spreading resistance sensitivity to quantify the anisotropic resistivity of these layered materials and connect to previous macroscopic transport observations.}, number={24}, journal={PHYSICAL REVIEW B}, author={Frick, Jordan R. and Sridhar, Samanvitha and Khansari, Ario and Comstock, Andrew H. and Norman, Elizabeth and O'Donnell, Shaun and Maggard, Paul A. and Sun, Dali and Dougherty, Daniel B.}, year={2023}, month={Dec} }
 @article{gabilondo_newell_broughton_koldemir_poettgen_jones_maggard_2023, title={Switching Lead for Tin in PbHfO<sub>3</sub>: Noncubic Structure of SnHfO<sub>3</sub>}, volume={9}, ISSN={["1521-3773"]}, DOI={10.1002/anie.202312130}, abstractNote={The removal of lead from commercialized perovskite-oxide-based piezoceramics has been a recent major topic in materials research owing to legislation in many countries. In this regard, Sn(II)-perovskite oxides have garnered keen interest due to their predicted large spontaneous electric polarizations and isoelectronic nature for substitution of Pb(II) cations. However, they have not been considered synthesizable owing to their high metastability. Herein, the perovskite lead hafnate, i.e., PbHfO3 in space group Pbam, is shown to react with SnClF at a low temperature of 300 °C, and resulting in the first complete Sn(II)-for-Pb(II) substitution, i.e. SnHfO3. During this topotactic transformation, a high purity and crystallinity is conserved with Pbam symmetry, as confirmed by X-ray and electron diffraction, elemental analysis, and 119Sn Mössbauer spectroscopy. In situ diffraction shows SnHfO3 also possesses reversible phase transformations and is potentially polar between ~130-200 °C. This so-called 'de-leadification' is thus shown to represent a highly useful strategy to fully remove lead from perovskite-oxide-based piezoceramics and opening the door to new explorations of polar and antipolar Sn(II)-oxide materials.}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Gabilondo, Eric A. and Newell, Ryan J. and Broughton, Rachel and Koldemir, Aylin and Poettgen, Rainer and Jones, Jacob L. and Maggard, Paul A.}, year={2023}, month={Sep} }
 @article{genoux_pauly_rooney_choi_shang_mcguigan_fataftah_kayser_suhr_debeer_et al._2023, title={Well-Defined Iron Sites in Crystalline Carbon Nitride}, volume={145}, ISSN={["1520-5126"]}, DOI={10.1021/jacs.3c05417}, abstractNote={Carbon nitride materials can be hosts for transition metal sites, but Mössbauer studies on iron complexes in carbon nitrides have always shown a mixture of environments and oxidation states. Here we describe the synthesis and characterization of a crystalline carbon nitride with stoichiometric iron sites that all have the same environment. The material (formula C6N9H2Fe0.4Li1.2Cl, abbreviated PTI/FeCl2) is derived from reacting poly(triazine imide)·LiCl (PTI/LiCl) with a low-melting FeCl2/KCl flux, followed by anaerobic rinsing with methanol. X-ray diffraction, X-ray absorption and Mössbauer spectroscopies, and SQUID magnetometry indicate that there are tetrahedral high-spin iron(II) sites throughout the material, all having the same geometry. The material is active for electrocatalytic nitrate reduction to ammonia, with a production rate of ca. 0.1 mmol cm-2 h-1 and Faradaic efficiency of ca. 80% at -0.80 V vs RHE.}, number={38}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Genoux, Alexandre and Pauly, Magnus and Rooney, Conor L. and Choi, Chungseok and Shang, Bo and McGuigan, Scott and Fataftah, Majed S. and Kayser, Yves and Suhr, Simon C. B. and Debeer, Serena and et al.}, year={2023}, month={Sep}, pages={20739–20744} }
 @article{gabilondo_newell_chestnut_weng_jones_maggard_2022, title={Circumventing thermodynamics to synthesize highly metastable perovskites: nano eggshells of SnHfO3}, volume={11}, ISSN={["2516-0230"]}, DOI={10.1039/d2na00603k}, abstractNote={Sn(ii)-based perovskite oxides, being the subject of longstanding theoretical interest for the past two decades, have been synthesized for the first time in the form of nano eggshell particle morphologies. All past reported synthetic attempts have been unsuccessful owing to their metastable nature, i.e., by their thermodynamic instability towards decomposition to their constituent oxides. A new approach was discovered that finally provides an effective solution to surmounting this intractable synthetic barrier and which can be the key to unlocking the door to many other predicted metastable oxides. A low-melting KSn2Cl5 salt was utilized to achieve a soft topotactic exchange of Sn(ii) cations into a Ba-containing perovskite, i.e., BaHfO3 with particle sizes of ∼350 nm, at a low reaction temperature of 200 °C. The resulting particles exhibit nanoshell-over-nanoshell morphologies, i.e., with SnHfO3 forming as ∼20 nm thick shells over the surfaces of the BaHfO3 eggshell particles. Formation of the metastable SnHfO3 is found to be thermodynamically driven by the co-production of the highly stable BaCl2 and KCl side products. Despite this, total energy calculations show that Sn(ii) distorts from the A-site asymmetrically and randomly and the interdiffusion has a negligible impact on the energy of the system (i.e., layered vs. solid solution). Additionally, nano eggshell particle morphologies of BaHfO3 were found to yield highly pure SnHfO3 for the first time, thus circumventing the intrinsic ion-diffusion limits occurring at this low reaction temperature. In summary, these results demonstrate that the metastability of many theoretically predicted Sn(ii)-perovskites can be overcome by leveraging the high cohesive energies of the reactants, the exothermic formation of a stable salt side product, and a shortened diffusion pathway for the Sn(ii) cations.}, journal={NANOSCALE ADVANCES}, author={Gabilondo, Eric A. and Newell, Ryan J. and Chestnut, Jessica and Weng, James and Jones, Jacob L. and Maggard, Paul A.}, year={2022}, month={Nov} }
 @article{shang_zhao_choi_jia_pauly_wu_tao_zhong_harmon_maggard_et al._2022, title={Monolayer Molecular Functionalization Enabled by Acid-Base Interaction for High-Performance Photochemical CO2 Reduction}, volume={6}, ISSN={["2380-8195"]}, DOI={10.1021/acsenergylett.2c01147}, abstractNote={We report the development of a hybrid catalyst consisting of carbon nitride (CNx) and cobalt phthalocyanine tetracarboxylic acid (CoPc-COOH), which converts CO2 to CO with high reaction rate (1067 μmol/g·h) and high selectivity (over 98%), under simulated solar irradiation. The carboxylic acid substituents on the phthalocyanine ligands play a critical role as they bind to the amine groups of CNx to enable nearly ideal monolayer coverage of the molecular cocatalyst on the semiconductor surface and promote catalytic activity from the molecular complex. Specifically, the CNx/CoPc-COOH hybrid material achieves a reaction rate 16 times higher than a CNx material containing unsubstituted CoPc molecules. We further show that activation and deactivation of the CNx/CoPc-COOH composite, which are associated with the reduction and decomposition of CoPc-COOH, respectively, both proceed at a nearly constant rate regardless of the CO2 reduction reaction rate. The decoupling of charge carrier injection and CO2 reduction catalysis has important mechanistic implications for future performance optimization and materials design of photocatalysts for CO2 reduction.}, journal={ACS ENERGY LETTERS}, author={Shang, Bo and Zhao, Fengyi and Choi, Chungseok and Jia, Xiaofan and Pauly, Magnus and Wu, Yueshen and Tao, Zixu and Zhong, Yiren and Harmon, Nia and Maggard, Paul A. and et al.}, year={2022}, month={Jun} }
 @article{o'donnell_vali_rawat_maggard_huda_rajeshwar_2022, title={Perspective-Multinary Oxide Semiconductors for Solar Fuels Generation: Closing the Performance Gap between Theory and Practice}, volume={11}, ISSN={["2162-8777"]}, DOI={10.1149/2162-8777/ac689c}, abstractNote={
 We address the current state-of-the-art in the development of multinary oxides—a family of compounds that has long interested Prof. John B. Goodenough. Specifically, we focus on their use as photoelectrodes for solar fuels generation. Using optical data and assuming an idealized 100% incident photon-to-electron conversion efficiency, it is possible to project the maximum short-circuit photocurrent efficiency to be expected for a given oxide semiconductor. The performance gap between this theoretical value and that realized experimentally is shown to be sizable for all but a couple candidates. The technical issues underlying this gap and strategies for closing it are presented.}, number={5}, journal={ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY}, author={O'Donnell, Shaun and Vali, Abbas and Rawat, Abhishek and Maggard, Paul A. and Huda, Muhammad N. and Rajeshwar, Krishnan}, year={2022}, month={May} }
 @article{o'donnell_osborn_krishnan_block_koldemir_small_broughton_jones_pottgen_andersson_et al._2022, title={Prediction and Kinetic Stabilization of Sn(II)-Perovskite Oxide Nanoshells}, volume={8}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.2c02192}, abstractNote={The synthesis of kinetically stabilized, i.e., metastable, dielectric semiconductors, represents a major frontier within technologically important fields as compared to thermodynamically stable solids that have received considerably more attention. Of long-standing theoretical interest are Sn(II) perovskites [e.g., Sn(Zr1/2Ti1/2)O3 (SZT)], which are isoelectronic Pb-free analogues of Pb(Zr1/2Ti1/2)O3 (PZT), a commercial piezoelectric composition that is dominant in the electronics industry. Herein, we describe the synthesis of this metastable SZT dielectric through a low-temperature flux reaction technique. The SZT has been found, for the first time, to grow and to be stabilized as a nanoshell at the surfaces of Ba(Zr1/2Ti1/2)O3 (BZT) particles, i.e., forming as BZT–SZT core–shell particles, as a result of Sn(II) cation exchange. In situ powder X-ray diffraction (XRD) and transmission electron microscopy data show that the SZT nanoshells result from the controlled cation diffusion of Sn(II) cations into the BZT particles, with tunable thicknesses of ∼25–100 nm. The SZT nanoshell is calculated to possess a metastability of approximately −0.5 eV atom–1 with respect to decomposition to SnO, ZrO2, and TiO2 and cannot currently be prepared as stand-alone particles. Rietveld refinements of the XRD data are consistent with a two-phase BZT–SZT model, with each phase possessing a generally cubic perovskite-type structure and nearly identical lattice parameters. Mössbauer spectroscopic data (119Sn) are consistent with Sn(II) cations within the SZT nanoshells and an outer ∼5–10 nm surface region comprised of oxidized Sn(IV) cations from exposure to air and water. The optical band gap of the SZT shell was found to be ∼2.2 eV, which is red-shifted by ∼1.2 eV compared to that of BZT. This closing of the band gap was probed by X-ray photoelectron spectroscopy and found to stem from a shift of the valence band edge to higher energies (∼1.07 eV) as a result of the addition of the Sn 5s2 orbitals forming a new higher-energy valence band. In summary, a novel synthetic tactic is demonstrated to be effective in preparing metastable SZT and representing a generally useful strategy for the kinetic stabilization of other predicted, metastable dielectrics.}, journal={CHEMISTRY OF MATERIALS}, author={O'Donnell, Shaun and Osborn, D. J. and Krishnan, Gowri and Block, Theresa and Koldemir, Aylin and Small, Thomas D. and Broughton, Rachel and Jones, Jacob L. and Pottgen, Rainer and Andersson, Gunther G. and et al.}, year={2022}, month={Aug} }
 @article{yang_huang_cheng_maggard_whangbo_luan_deng_2022, title={Prediction of Large Second Harmonic Generation in the Metal-Oxide/Organic Hybrid Compound CuMoO3(p2c)}, volume={14}, ISSN={["2073-8994"]}, url={https://www.mdpi.com/2073-8994/14/4/824}, DOI={10.3390/sym14040824}, abstractNote={Noncentrosymmetric hybrid framework (HF) materials are an important system in discovering new practical second-order nonlinear optical materials. We calculated the second harmonic generation (SHG) response of a noncentrosymmetric (NCS) organic–inorganic HF compound, CuMoO3(p2c) (p2c = pyrazine-2-carboxylate) to find that it exhibits the largest SHG response among all known NCS HF materials with one-dimensional helical chains. Further atom response theory analysis revealed that the metal atoms Cu and Mo contribute much more strongly than do nonmetal atoms in determining the strength of the SHG response, which is a novel example in nonlinear optical materials known to date.}, number={4}, journal={SYMMETRY-BASEL}, author={Yang, Tingting and Huang, Xueli and Cheng, Xiyue and Maggard, Paul A. and Whangbo, Myung-Hwan and Luan, Chengkai and Deng, Shuiquan}, year={2022}, month={Apr} }
 @article{gabilondo_o'donnell_newell_broughton_mateus_jones_maggard_2022, title={Renaissance of Topotactic Ion-Exchange for Functional Solids with Close Packed Structures}, volume={4}, ISSN={["1521-3765"]}, DOI={10.1002/chem.202200479}, abstractNote={Abstract Recently, many new, complex, functional oxides have been discovered with the surprising use of topotactic ion‐exchange reactions on close‐packed structures, such as found for wurtzite, rutile, perovskite, and other structure types. Despite a lack of apparent cation‐diffusion pathways in these structure types, synthetic low‐temperature transformations are possible with the interdiffusion and exchange of functional cations possessing ns 2 stereoactive lone pairs (e. g., Sn(II)) or unpaired nd x electrons (e. g., Co(II)), targeting new and favorable modulations of their electronic, magnetic, or catalytic properties. This enables a synergistic blending of new functionality to an underlying three‐dimensional connectivity, i. e., [‐M−O‐M‐O‐] n , that is maintained during the transformation. In many cases, this tactic represents the only known pathway to prepare thermodynamically unstable solids that otherwise would commonly decompose by phase segregation, such as that recently applied to the discovery of many new small bandgap semiconductors.}, journal={CHEMISTRY-A EUROPEAN JOURNAL}, author={Gabilondo, Eric and O'Donnell, Shaun and Newell, Ryan and Broughton, Rachel and Mateus, Marcelo and Jones, Jacob L. and Maggard, Paul A.}, year={2022}, month={Apr} }
 @article{o'donnell_smith_carbone_maggard_2022, title={Structure, Stability, and Photocatalytic Activity of a Layered Perovskite Niobate after Flux-Mediated Sn(II) Exchange}, volume={61}, ISSN={["1520-510X"]}, DOI={10.1021/acs.inorgchem.1c03846}, abstractNote={A new strategy to incorporate the Sn(II) cation and its stereoactive lone pair into the structure of a photocatalytic oxide has been achieved by leveraging the asymmetric coordination environments within the (111)-oriented perovskite-type layers of Ba5Nb4O15. This layered perovskite represents one of the few known photocatalysts capable of efficiently splitting water, but its activity is restricted to ultraviolet radiation owing to its large band gap. By reacting this layered niobate at 350 °C for 24 h within a low-melting SnCl2/SnF2 salt, the new (Ba1-xSnx)Nb4O15 (x = 0-0.5; P3̅m1; a = 5.79650(5) Å, c = 11.79288(8) Å; Z = 2) has been prepared in high purity with up to ∼50% Sn(II) cations. Statistical disordering of the Sn(II) cations was probed by neutron diffraction Rietveld refinements and found to occur predominantly over the asymmetric cation sites, Ba2 and Ba3, for the 40% Sn(II) composition of x = 0.4. An increasing Sn(II) amount significantly red-shifts the band gap (Eg) from 0% Sn for x = 0 (3.78 eV; ultraviolet, indirect) to 40% Sn for x = 0.4 (Eg = 2.35 eV; visible, indirect), as found by UV-vis diffuse reflectance. Density functional theory calculations show an increasing metastability, i.e., a thermodynamic instability toward decomposition to the simpler oxides SnO, Nb2O5, and SnNb2O6. A synthetic limit of ∼50% Sn(II) cations can be kinetically stabilized under these reaction conditions. For the highest Sn(II) amounts, photocatalytic rates are observed for the production of molecular oxygen from water of up to ∼77 μmol O2 h-1 g-1 (visible irradiation) and ∼159 μmol O2 h-1 g-1 (UV-vis irradiation), with apparent quantum yields of ∼0.35 and 0.52%, respectively. By comparison, pure Ba5Nb4O15 exhibits no measurable photocatalytic activity under visible-light irradiation. Electronic structure calculations show that the decreased band gap stems from the introduction of the Sn(II) cations and the formation of a higher-energy valence band arising from the filled 5s2 valence orbitals. Thus, visible-light bandgap excitation occurs from electronic transitions predominantly involving the Sn(II) (5s2) to Nb(V) (4d0) cations. This study demonstrates the new and powerful utility of low-temperature Sn(II)-exchange reactions to sensitize layer-type oxide photocatalysts to the visible region of the solar spectrum, which is facilitated by exploiting their asymmetric cation environments.}, number={9}, journal={INORGANIC CHEMISTRY}, author={O'Donnell, Shaun and Smith, Avery and Carbone, Abigail and Maggard, Paul A.}, year={2022}, month={Mar}, pages={4062–4070} }
 @article{pauly_kroeger_duppel_murphey_cahoon_lotsch_maggard_2022, title={Unveiling the complex configurational landscape of the intralayer cavities in a crystalline carbon nitride}, volume={2}, ISSN={["2041-6539"]}, DOI={10.1039/d1sc04648a}, abstractNote={The in-depth understanding of the reported photoelectrochemical properties of the layered carbon nitride, poly(triazine imide)/LiCl (PTI/LiCl), has been limited by the apparent disorder of the Li/H atoms within its framework. To understand and resolve the current structural ambiguities, an optimized one-step flux synthesis (470 °C, 36 h, LiCl/KCl flux) was used to prepare PTI/LiCl and deuterated-PTI/LiCl in high purity. Its structure was characterized by a combination of neutron/X-ray diffraction and transmission electron microscopy. The range of possible Li/H atomic configurations was enumerated for the first time and, combined with total energy calculations, reveals a more complex energetic landscape than previously considered. Experimental data were fitted against all possible structural models, exhibiting the most consistency with a new orthorhombic model (Sp. Grp. Ama2) that also has the lowest total energy. In addition, a new Cu(i)-containing PTI (PTI/CuCl) was prepared with the more strongly scattering Cu(i) cations in place of Li, and most closely matching with the partially-disorder structure in Cmc21. Thus, a complex configurational landscape of PTI is revealed to consist of a number of ordered crystalline structures that are new potential synthetic targets, such as with the use of metal-exchange reactions.}, journal={CHEMICAL SCIENCE}, author={Pauly, Magnus and Kroeger, Julia and Duppel, Viola and Murphey, Corban and Cahoon, James and Lotsch, Bettina V and Maggard, Paul A.}, year={2022}, month={Feb} }
 @article{sohag_o'donnell_fuoco_maggard_2021, title={A Metastable p-Type Semiconductor as a Defect-Tolerant Photoelectrode}, volume={26}, ISSN={["1420-3049"]}, url={https://www.mdpi.com/1420-3049/26/22/6830}, DOI={10.3390/molecules26226830}, abstractNote={A p-type Cu3Ta7O19 semiconductor was synthesized using a CuCl flux-based approach and investigated for its crystalline structure and photoelectrochemical properties. The semiconductor was found to be metastable, i.e., thermodynamically unstable, and to slowly oxidize at its surfaces upon heating in air, yielding CuO as nano-sized islands. However, the bulk crystalline structure was maintained, with up to 50% Cu(I)-vacancies and a concomitant oxidation of the Cu(I) to Cu(II) cations within the structure. Thermogravimetric and magnetic susceptibility measurements showed the formation of increasing amounts of Cu(II) cations, according to the following reaction: Cu3Ta7O19 + x/2 O2 → Cu(3−x)Ta7O19 + x CuO (surface) (x = 0 to ~0.8). With minor amounts of surface oxidation, the cathodic photocurrents of the polycrystalline films increase significantly, from <0.1 mA cm−2 up to >0.5 mA cm−2, under visible-light irradiation (pH = 6.3; irradiant powder density of ~500 mW cm−2) at an applied bias of −0.6 V vs. SCE. Electronic structure calculations revealed that its defect tolerance arises from the antibonding nature of its valence band edge, with the formation of defect states in resonance with the valence band, rather than as mid-gap states that function as recombination centers. Thus, the metastable Cu(I)-containing semiconductor was demonstrated to possess a high defect tolerance, which facilitates its high cathodic photocurrents.}, number={22}, journal={MOLECULES}, author={Sohag, Zahirul and O'Donnell, Shaun and Fuoco, Lindsay and Maggard, Paul A.}, year={2021}, month={Nov} }
 @misc{maggard_2021, title={Capturing Metastable Oxide Semiconductors for Applications in Solar Energy Conversion}, volume={54}, ISSN={["1520-4898"]}, DOI={10.1021/acs.accounts.1c00210}, abstractNote={ConspectusMany small bandgap semiconductors have been discovered or predicted to exist beyond the edges of stability, that is, accessible only as metastable solids that are thermodynamically unstable. In many cases, these metastable semiconductors have been revealed to have technologically promising properties for solar energy conversion, such as in photocatalysis or in photovoltaics. This Account presents a review of research results selected from my group and others in recent years on these semiconductors. Notably, these include the chemical systems of mixed-metal oxides (i.e., M'MOx; M = Ti(IV), Nb(V), or Ta(V) cation; M' = Ag(I), Cu(I), Sn(II), Pb(II), or Bi(III) cation), which have diverse structure types and compositions. High photocatalytic activities have been found for the light-driven reduction or oxidation of water as p- or n-type photoelectrodes, respectively, or as suspended powders in aqueous solutions. These have exhibited new combinations of favorable semiconductor properties, such as deep visible-light absorption, near-optimal band edge energies, defect tolerance, and functional carrier mobilities and charge separation. As described herein, this set of properties is inextricably linked to their metastable nature, that is, the crystalline structures and compositions needed for these characteristics lead naturally to thermodynamic instabilities.This Account focuses on current research efforts that have begun unlocking the potential of these semiconductors via new recent advances in (1) synthetic approaches that enable their preparation and (2) the understanding of structure-property relationships discovered at the precipices of stability that lead to the improved semiconductor properties. For example, low-temperature reactions have been developed to facilitate greater kinetic control, such as with the use of molten salts, and have been a key factor in preparing many of these semiconductors. As a result, a plethora of promising new mixed-metal oxide systems have been uncovered that exhibit band gaps spanning the range of photon energies from ∼1.3 to >3.0 eV. Especially relevant for visible-light applications are the Cu(I)- and Sn(II)-containing semiconductors. For example, n-type Sn(II)-titanates and p-type Cu(I)-niobates can be synthesized by flux methods and exhibit some of the smallest known visible-light band gaps that also maintain suitable conduction and valence band edges for driving the water-splitting half reactions. Kinetic stabilization of these metastable semiconductors against thermally driven phase segregation is increased with the formation of solid solutions for both the M and M' cation sites, leading to effective strategies to more finely tune their band gaps, band edge energies, and photoelectrochemical properties. Many unique and useful relationships are emerging between the synthesis and structures of metastable semiconductors and their physical properties, leading to more efficient solar energy conversion.}, number={16}, journal={ACCOUNTS OF CHEMICAL RESEARCH}, author={Maggard, Paul A.}, year={2021}, month={Aug}, pages={3160–3171} }
 @inbook{maggard_2021, place={Boston, MA}, title={Discovery and Development of Semiconductors for Photoelectrochemical Energy Conversion}, ISBN={978-3-030-63712-5}, booktitle={Springer Handbook of Inorganic Photochemistry}, publisher={Springer Nature}, author={Maggard, P.A.}, editor={Sharp, Ian and Spitler, MarkEditors}, year={2021} }
 @article{rajeshwar_maggard_o'donnell_2021, title={In Search of the "Perfect" Inorganic Semiconductor/Liquid Interface for Solar Water Splitting}, volume={30}, ISSN={["1944-8783"]}, DOI={10.1149/2.F07211IF}, abstractNote={Arguably, one would be hard-pressed to envision a more ideal renewable energy conversion system than the solar splitting of water. The energy-rich product, hydrogen, may be stored and used later on-demand for generating power either via combustion or in a fuel cell. In scenarios where dioxygen is needed for respiration (e.g., space travel), CO 2 may be used instead of water as the reactant feed. Both these applications require a photon absorber for capturing sunlight, and an inorganic semiconductor fulfills this function. Therefore, a photoelectrochemical (PEC) system may be devised based on an n - or p-type semiconductor electrode in contact with the reactant fluid. On bandgap excitation of the photoelectrode, the generated holes or electrons respectively are used to drive the oxidation or reduction of the reactant species. In the case of water splitting, these are the OH - or H 3 O + ions, respectively. In a CO 2 photoreduction system, the corresponding species are OH - and (dissolved) CO 2 . In both cases, the analogy with a plant photosynthesis system is direct.}, number={1}, journal={ELECTROCHEMICAL SOCIETY INTERFACE}, author={Rajeshwar, Krishnan and Maggard, Paul A. and O'Donnell, Shaun}, year={2021}, month={Mar} }
 @article{gabilondo_o'donnell_broughton_jones_maggard_2021, title={Synthesis and stability of Sn(II)-containing perovskites: (Ba,Sn-II)(HfO3)-O-IV versus (Ba,Sn-II)(SnO3)-O-IV}, volume={302}, ISSN={["1095-726X"]}, DOI={10.1016/j.jssc.2021.122419}, abstractNote={While Sn(II)-containing perovskite oxides have long drawn attention as Pb(II) substitutes in technologically-relevant dielectric materials, they are also highly thermodynamically unstable and potentially impossible to prepare. Investigations into the new flux-mediated syntheses of metastable Sn(II)-containing hafnate and stannate perovskites were aimed at understanding the key factors related to their synthesizability. The BaHfO3 perovskite was reacted with SnClF from 250 to 350 ​°C for 12–72 ​h, yielding an unprecedented Sn(II) concentration on the A-site of up to ~70 ​mol%, i.e., (Ba0.3Sn0.7)HfO3 in high purity. Elemental mapping using EDS shows the Sn(II) cations diffuse gradually throughout the crystallites, with two reaction cycles needed to give a nearly homogeneous distribution. In contrast, similar reactions with BaSnO3 and as little as 10 ​mol% Sn(II) result in decomposition to SnO, SnO2, and BaSnO3. The (Ba1-xSnx)HfO3 compositions exhibit a primary cubic perovskite structure (Pm3¯m; for x ​= ​1/3, 1/2 and 2/3) by powder X-ray diffraction (XRD) methods, with the Sn(II) cations substituted on the A-site. Total energy calculations show the thermodynamic instability versus the ground state (i.e., metastability) for (Ba1-xSnx)HfO3 increases with Sn(II) substitution, reaching a maximum of ~446 ​meV atom−1 at ~70 ​mol% Sn(II). The decomposition pathway of (Ba1/3Sn2/3)HfO3 was probed by ex situ XRD as well as in situ electron microscopy methods. An onset of thermally-induced decomposition begins at ~350–400 ​°C to give the more stable oxides which are found to segregate out in surface layers. These results help to elucidate the factors underpinning the synthesizability of highly metastable Sn(II)-containing perovskites, which increases with their cohesive energy and with the absence of lower-energy polymorphs or other ground states that can be reached without significant ion diffusion.}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Gabilondo, Eric A. and O'Donnell, Shaun and Broughton, Rachel and Jones, Jacob L. and Maggard, Paul A.}, year={2021}, month={Oct} }
 @article{nevola_bataller_kumar_sridhar_frick_o'donnell_ade_maggard_kemper_gundogdu_et al._2021, title={Timescales of excited state relaxation in alpha-RuCl3 observed by time-resolved two-photon photoemission spectroscopy}, volume={103}, ISSN={["2469-9969"]}, url={https://doi.org/10.1103/PhysRevB.103.245105}, DOI={10.1103/PhysRevB.103.245105}, abstractNote={The nonequilibrium properties of strongly correlated materials present a target in the search for new phases of matter. It is important to observe the types of excitations that exist in these materials and their associated relaxation dynamics. We have studied the photoexcitations in a spin-orbit assisted Mott insulator $\ensuremath{\alpha}\text{\ensuremath{-}}\mathrm{Ru}{\mathrm{Cl}}_{3}$ using time-resolved two-photon photoemission spectroscopy and transient reflection spectroscopy. We find that photoexcited carriers (doublons) in the upper Hubbard band rapidly relax to Mott-Hubbard excitons on a timescale of less than 200 fs. Subsequently, further relaxation of these lower-energy quasiparticles occurs with an energy-dependent time constant of that ranges from 370 to 600 fs due to exciton cooling. The population of Mott-Hubbard excitons persists for timescales up to several microseconds.}, number={24}, journal={PHYSICAL REVIEW B}, author={Nevola, Dan and Bataller, Alexander and Kumar, Ankit and Sridhar, Samanvitha and Frick, Jordan and O'Donnell, Shaun and Ade, Harald and Maggard, Paul A. and Kemper, Alexander F. and Gundogdu, Kenan and et al.}, year={2021}, month={Jun} }
 @article{frick_sridhar_o'donnell_maggard_dougherty_2020, title={An interface-controlled Mott memristor in α-RuCl3}, volume={116}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/5.0009670}, DOI={10.1063/5.0009670}, abstractNote={Memristor devices have history-dependent charge transport properties that are ideal for neuromorphic computing applications. We reveal a memristor material and mechanism in the layered Mott insulator α-RuCl3. The pinched hysteresis loops and S-shaped negative differential resistance in bulk crystals verify memristor behavior and are attributed to a nonlinear coupling between charge injection over a Schottky barrier at the electrical contacts and concurrent Joule heating. Direct simulations of this coupling can reproduce the device characteristics.}, number={18}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Frick, Jordan R. and Sridhar, Samanvitha and O'Donnell, Shaun and Maggard, Paul A. and Dougherty, Daniel B.}, year={2020}, month={May}, pages={183501} }
 @article{hamilton_o'donnell_zoellner_sullivan_maggard_2020, title={Flux‐mediated synthesis and photocatalytic activity of NaNbO
            3
            particles}, volume={103}, ISSN={0002-7820 1551-2916}, url={http://dx.doi.org/10.1111/jace.16765}, DOI={10.1111/jace.16765}, abstractNote={Abstract Using molten‐salt synthetic techniques, NaNbO 3 (Space group Pbcm ; No. 57) was prepared in high purity at a reaction time of 12 hours and a temperature of 900°C. All NaNbO 3 products were prepared from stoichiometric ratios of Nb 2 O 5 and Na 2 CO 3 together with the addition of a salt flux introduced at a 10:1 molar ratio of salt to NaNbO 3 , that is, using the Na 2 SO 4 , NaF, NaCl, and NaBr salts. A solid‐state synthesis was performed in the absence of a molten salt to serve as a control. The reaction products were all found to be phase pure through powder X‐ray diffraction, for example, with refined lattice constants of a = 5.512(5) Å, b = 5.567(3) Å, and c = 15.516(8) Å from the Na 2 SO 4 salt reaction. The products were characterized using UV‐Vis diffuse reflectance spectroscopy to have a bandgap size of ~3.5 eV. The particles sizes were analyzed by scanning electron microscopy (SEM) and found to be dependent upon the flux type used, from ~<1 μm to >10 μm in length, with overall surface areas that could be varied from 0.66 m 2 /g (for NaF) to 1.55 m 2 /g (for NaBr). Cubic‐shaped particle morphologies were observed for the metal halide salts with the set of exposed (100)/(010)/(001) crystal facets, while a truncated octahedral morphology formed in the sodium sulfate salt reaction with predominantly the set of (110)/(101)/(011) crystal facets. The products were found to be photocatalytically active for hydrogen production under UV‐Vis irradiation, with the aid of a 1 wt% Pt surface cocatalyst. The platinized NaNbO 3 particles were suspended in an aqueous 20% methanol solution and irradiated by UV‐Vis light ( λ > 230 nm). After 6 hours of irradiation, the average total hydrogen production varied with the particle morphologies and sizes, with 753 µmol for Na 2 SO 4 , 334 µmol for NaF, 290 µmol for NaCl, 81 µmol for NaBr, and 249 µmol for the solid‐state synthesized NaNbO 3 . These trends show a clear relationship to particle sizes, with smaller particles showing higher photocatalytic activity in the order of NaF > NaCl > NaBr. Furthermore, the particle morphologies obtained from the Na 2 SO 4 flux showed even higher photocatalytic activity, though having a relatively similar overall surface area, owing to the higher activity of the (110) crystal facets. The apparent quantum yield (100 mW/cm 2 , λ = 230 to 350 nm, pH = 7) was measured to be 3.7% for NaNbO 3 prepared using the NaF flux, but this was doubled to 6.8% when prepared using the Na 2 SO 4 flux. Thus, these results demonstrate the powerful utility of flux synthetic techniques to control particle sizes and to expose higher‐activity crystal facets to boost their photocatalytic activities for molecular hydrogen production.}, number={1}, journal={Journal of the American Ceramic Society}, publisher={Wiley}, author={Hamilton, Adam M. and O'Donnell, Shaun and Zoellner, Brandon and Sullivan, Ian and Maggard, Paul A.}, year={2020}, month={Jan}, pages={454–464} }
 @inbook{maggard_2020, title={Photoelectrochemical Materials for Solar Energy Conversion}, booktitle={Comprehensive Inorganic Chemistry III}, publisher={Elsevier}, author={Maggard, P.A.}, editor={Woodward, Pat and Halasyamani, ShivEditors}, year={2020} }
 @article{maggard_chen_deng_whangbo_2020, title={Physical Properties of Molecules and Condensed Materials Governed by Onsite Repulsion, Spin-Orbit Coupling and Polarizability of their Constituent Atoms}, volume={25}, ISSN={["1420-3049"]}, url={https://www.mdpi.com/1420-3049/25/4/867}, DOI={10.3390/molecules25040867}, abstractNote={The onsite repulsion, spin–orbit coupling and polarizability of elements and their ions play important roles in controlling the physical properties of molecules and condensed materials. In celebration of the 150th birthday of the periodic table this year, we briefly review how these parameters affect the physical properties and are interrelated.}, number={4}, journal={Molecules}, author={Maggard, P.A. and Chen, X. and Deng, S. and Whangbo, M}, year={2020}, pages={867} }
 @article{o’donnell_chung_carbone_broughton_jones_maggard_2020, title={Pushing the Limits of Metastability in Semiconducting Perovskite Oxides for Visible-Light-Driven Water Oxidation}, volume={32}, ISSN={0897-4756 1520-5002}, url={http://dx.doi.org/10.1021/acs.chemmater.0c00044}, DOI={10.1021/acs.chemmater.0c00044}, abstractNote={A synthetic route has been discovered to thermodynamically unstable, i.e., metastable, Sn(II)–perovskite oxides that have been highly sought after as lead-free dielectrics and small bandgap semicon...}, number={7}, journal={Chemistry of Materials}, publisher={American Chemical Society (ACS)}, author={O’Donnell, Shaun and Chung, Ching-Chang and Carbone, Abigail and Broughton, Rachel and Jones, Jacob L. and Maggard, Paul A.}, year={2020}, month={Mar}, pages={3054–3064} }
 @article{luo_chen_maggard_2020, title={Rare example of chiral and achiral polymorphs of a metal-oxide/organic hybrid compound}, volume={287}, ISSN={["1095-726X"]}, DOI={10.1016/j.jssc.2020.121358}, abstractNote={Hydrothermal techniques have been used to prepare two new Cu(I)/Mo(VI)-oxide hybrids that represent a rare example of crystallization of both achiral (1) and chiral (2) polymorphic structures with the composition CuMoO3(p2c) (p2c ​= ​pyrazine-2-carboxylate). Their structures were characterized by single-crystal X-ray diffraction (1 - space group: P21/c, Z ​= ​4; a ​= ​8.4965(3) Å, b ​= ​12.7471(5) Å, c ​= ​7.2850(3) Å), β ​= ​97.147(2)o, and 2 - P32, Z ​= ​3, a ​= ​7.6789(2) Å, c ​= ​10.9164(5) Å) and found to consist of highly-distorted MoO5N octahedra that are vertex-bridged to form -O-Mo-O-Mo-O- chains and connected to each other via the coordinating p2c ligands and Cu(I) cations. In the achiral structure of 1, the p2c ligands and Cu(I) cations are coordinated to a single side of the extended -O-Mo-O-Mo-O- chains. In the chiral structure of 2, by contrast, these coordinate via a helical-type arrangement down the 32 screw axis with a rotation of 120° between neighboring octahedra. The chiral polymorph is favored with higher pressure and exhibits a correspondingly higher density owing to the greater packing efficiency of the helical chains, with calculated densities (g cm−3) of 2.81 and 2.95 for 1 and 2, respectively. Both are found to have nearly identical band gaps of ~1.37 ​eV, which are significantly smaller than in other related Cu/Mo oxides . Density functional theory calculations show that 1 exhibits a slightly lower energy of ~89 ​meV per formula (or ~8.6 ​kJ ​mol−1) as compared to 2 and is thus energetically favored. Given the higher calculated energy of the chiral polymorph, 2, this suggests that the application of higher pressures can provide a convenient driving force for the crystallization of higher-density, helical-chain structures that are noncentrosymmetric.}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Luo, Lan and Chen, Yunhua and Maggard, Paul A.}, year={2020}, month={Jul} }
 @article{batra_tran_johnson_zoellner_maggard_jones_rossetti_ramprasad_2020, title={Search for Ferroelectric Binary Oxides: Chemical and Structural Space Exploration Guided by Group Theory and Computations}, volume={32}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.9b05324}, abstractNote={The presence of bistable polarization states along with accessible switching capabilities lend ferroelectrics as the ideal candidates for a variety of applications. Although many conventional ferro...}, number={9}, journal={CHEMISTRY OF MATERIALS}, author={Batra, Rohit and Tran, Huan Doan and Johnson, Brienne and Zoellner, Brandon and Maggard, Paul A. and Jones, Jacob L. and Rossetti, George A., Jr Jr and Ramprasad, Rampi}, year={2020}, month={May}, pages={3823–3832} }
 @article{o'donnell_hamilton_maggard_2019, title={Fast Flux Reaction Approach for the Preparation of Sn2TiO4: Tuning Particle Sizes and Photocatalytic Properties}, volume={166}, ISSN={["1945-7111"]}, DOI={10.1149/2.0141905jes}, abstractNote={The Sn 2 TiO 4 phase is a small-bandgap (E g ∼ 1.6 eV) semiconductor with suitable band energies to drive photocatalytic water- splitting. A new fast flux reaction can be used to prepare high purity Sn 2 TiO 4 in reaction times of down to 5 minutes. Shorter reaction times (5 and 15 min) lead to nanosized particles while longer reaction times (24 hours) yield micron-sized particles. The nanoparticles show an increased bandgap size owing to quantum size effects in the weak confinement regime (r >> a B ), increasing by ∼ 0.3 eV from 1.60 eV to 1.89 eV (indirect). From Mott-Schottky analyses, the conduction band edge is found to shift to slightly more negative potentials while the valence band edge exhibits a relatively larger positive shift. Calculations show this arises from the more disperse Sn s -orbital bands at the top of the valence band, compared the large Ti-based d -orbital band at the bottom of the conduction band. The photocatalytic activities of the Sn 2 TiO 4 nanoparticles for molecular hydrogen and oxygen production showed higher rates than the equivalent micron-sized particles as a result of both higher surface areas and higher overpotentials to drive each of the half reactions.}, number={5}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={O'Donnell, Shaun and Hamilton, Adam and Maggard, Paul A.}, year={2019}, month={Jan}, pages={H3084–H3090} }
 @article{kumar_o'donnell_slang_maggard_wang_2019, title={Harnessing Plasmon-Induced Hot Carriers at the Interfaces with Ferroelectrics}, volume={7}, ISSN={["2296-2646"]}, DOI={10.3389/fchem.2019.00299}, abstractNote={This article reviews the scientific understanding and progress of interfacing plasmonic particles with ferroelectrics in order to facilitate the absorption of low-energy photons and their conversion to chemical fuels. The fundamental principles of hot carrier generation and charge injection are described for semiconductors interfaced with metallic nanoparticles and immersed in aqueous solutions, forming a synergistic juncture between the growing fields of plasmonically-driven photochemistry and semiconductor photocatalysis. The underlying mechanistic advantages of a metal-ferroelectric vs. metal-nonferroelectric interface are presented with respect to achieving a more optimal and efficient control over the Schottky barrier height and charge separation. Notable recent examples of using ferroelectric-interfaced plasmonic particles have demonstrated their roles in yielding significantly enhanced photocurrents as well as in the photon-driven production of molecular hydrogen. Notably, plasmonically-driven photocatalysis has been shown to occur for photon wavelengths in the infrared range, which is at lower energies than typically possible for conventional semiconductor photocatalysts. Recent results thus demonstrate that integrated ferroelectric-plasmonic systems represent a potentially transformative concept for use in the field of solar energy conversion.}, number={299}, journal={Frontiers in Chemistry}, author={Kumar, V and O'Donnell, S.C. and Slang, D.L. and Maggard, P.A. and Wang, G.}, year={2019}, month={May}, pages={1–19} }
 @article{zoellner_o'donnell_wu_itanze_carbone_osterloh_geyer_maggard_2019, title={Impact of Nb(V) Substitution on the Structure and Optical and Photoelectrochemical Properties of the Cu-5(Ta1-xNbx)(11)O-30 Solid Solution}, volume={58}, ISSN={["1520-510X"]}, DOI={10.1021/acs.inorgchem.9b00304}, abstractNote={A family of solid solutions, Cu5(Ta1- xNb x)11O30 (0 ≤ x ≤ 0.4), was investigated as p-type semiconductors for their band gaps and energies and for their activity for the reduction of water to molecular hydrogen. Compositions from 0 to 40 mol % niobium were prepared in high purity by solid-state methods, accompanied by only very small increases in the lattice parameters of ∼0.05% and with the niobium and tantalum cations disordered over the same atomic sites. However, an increasing niobium content causes a significant decrease in the bandgap size from ∼2.58 to ∼2.05 eV owing to the decreasing conduction band energies. Linear-sweep voltammetry showed an increase in cathodic photocurrents with niobium content and applied negative potential of up to -0.6 mA/cm2 (pH ∼7.3; AM 1.5 G light filter with an irradiation intensity of ∼100 mW/cm2). The cathodic photocurrents could be partially stabilized by heating the polycrystalline films in air at 550 °C for 1 h to produce surface nanoislands of CuO or using protecting layers of aluminum-doped zinc oxide and titania. Aqueous suspensions of the Cu5(Ta1- xNb x)11O30 powders were also found to be active for hydrogen production under visible-light irradiation in a 20% aqueous methanol solution with the highest apparent quantum yields for the 10% and 20% Nb-substituted samples. Electronic structure calculations show that the increased photocurrents and hydroen evolution activities of the solid solutions arise near the percolation threshold of the niobate/tantalate framework wherein the Nb cations establish an extended -O-Nb-O-Nb-O- diffusion pathway for the minority carriers. The latter also reveals a novel pathway for enhancing charge separation as a function of the niobium-oxide connectivity. Thus, these results illustrate the advantages of using solid solutions to achieve the smaller bandgap sizes and band energies that are needed for solar-driven photocatalytic reactions.}, number={10}, journal={INORGANIC CHEMISTRY}, author={Zoellner, Brandon and O'Donnell, Shaun and Wu, Zongkai and Itanze, Dominique and Carbone, Abigail and Osterloh, Frank E. and Geyer, Scott and Maggard, Paul A.}, year={2019}, month={May}, pages={6845–6857} }
 @article{kumar_o'donnell_zoellner_martinez_wang_maggard_2019, title={Interfacing Plasmonic Nanoparticles with Ferroelectrics for Hot-Carrier-Driven Photocatalysis: Impact of Schottky Barrier Height}, volume={2}, ISSN={["2574-0962"]}, DOI={10.1021/acsaem.9b01682}, abstractNote={Emergent strategies for efficient solar energy conversion have focused on ways to harness photons in the lower-energy range of sunlight that cannot be utilized by conventional semiconductor photocatalyst systems. Recent research has demonstrated that interfaced plasmonic–ferroelectric particles represent a promising strategy for the utilization of near-infrared (NIR) light owing to the possibility of the more efficient injection of hot charge carriers from noble metal nanoparticles. Described herein, platinum-end-capped gold nanorods (AuNRs) function as antennae to absorb low-energy NIR photons to generate hot electrons that can be injected into ferroelectric PbZrxTi1–xO3 (PZT; x = 0.48, 0.50, 0.52, 0.54, 0.56, and 0.60) and drive the reduction of water to molecular hydrogen at its surfaces. As an aqueous suspension, the interfaced AuNR-PZT particles exhibited maximal photocatalytic rates for hydrogen formation under a 976 nm diode laser (powder density = 2.0 W cm–2) for the 52% Zr (x = 0.52) composition ...}, number={10}, journal={ACS APPLIED ENERGY MATERIALS}, author={Kumar, Vineet and O'Donnell, Shaun and Zoellner, Brandon and Martinez, Jhon and Wang, Gufeng and Maggard, Paul A.}, year={2019}, month={Oct}, pages={7690–7699} }
 @article{zoellner_hou_carbone_kiether_markham_cuomo_maggard_2018, title={Activating the Growth of High Surface Area Alumina Using a Liquid Galinstan Alloy}, volume={3}, ISSN={["2470-1343"]}, DOI={10.1021/acsomega.8b02442}, abstractNote={The growth of high surface area alumina has been investigated with the use of a liquid Galinstan alloy [66.5% (wt %) Ga, 20.5% In and 13.0% Sn] as an activator for aluminum. In this process, the aluminum is slowly dissolved into the gallium-indium-tin alloy, which is then selectively oxidized at ambient temperature and pressure under a humid stream of flowing CO2 or N2 to yield amorphous alumina. This preparative route represents a simple and low toxicity approach to obtain amorphous high surface area alumina with very low water content. The as-synthesized high surface area alumina aerogel was a blue-colored solid owing to the Rayleigh scattering by its dendritic fibrous nanostructure consisting of mainly alumina with small amounts of water. Upon annealing at 850 °C, the amorphous product transformed into γ-Al2O3, as well as θ-Al2O3 upon annealing at 1050 °C. Elemental analysis by energy-dispersive spectroscopy provides further evidence that the high surface area alumina is composed of only aluminum and oxygen. The surface area of the amorphous alumina varied from ∼79 to ∼140 m2/g, depending on the initial weight percentage of aluminum used in the alloy. A correlation between the initial concentration of aluminum in the alloy and the surface area of the alumina product was found to peak at ∼30% Al. These results suggest a novel route to the formation of amorphous alumina aerogel-type materials.}, number={12}, journal={ACS OMEGA}, author={Zoellner, Brandon and Hou, Feier and Carbone, Abigail and Kiether, William and Markham, Keith and Cuomo, Jerome and Maggard, Paul A.}, year={2018}, month={Dec}, pages={16409–16415} }
 @article{ortiz_zoellner_kumar_janelli_tang_maggard_wang_2018, title={Composite Ferroelectric and Plasmonic Particles for Hot Charge Separation and Photocatalytic Hydrogen Gas Production}, volume={1}, ISSN={["2574-0962"]}, DOI={10.1021/acsaem.8b00772}, abstractNote={Plasmonic nanoparticles are excellent light absorbers for harvesting solar energy, resulting in hot electrons that can be utilized in photocatalytic hydrogen production. However, the hot electrons generated in a localized surface plasmon resonance process have a very short lifetime and are challenging to use efficiently. Herein, using near IR light irradiation, we show that by combining gold nanorods (AuNRs) with ferroelectric PbTiO3 particles that possess a large remanent electric dipole moment, hot charges generated on plasmonic particles can be injected into ferroelectric materials and drive the photocatalysis reaction. Compared to metallic Pt-end-capped AuNRs, the efficiency of using hot electrons for photocatalytic reactions is enhanced for the composite catalyst, which improves the light-to-chemical energy conversion efficiencies by about 1 order of magnitude for the same amount of plasmonic particles being used.}, number={9}, journal={ACS APPLIED ENERGY MATERIALS}, author={Ortiz, Nathalia and Zoellner, Brandon and Kumar, Vineet and Janelli, Tara and Tang, Shuli and Maggard, Paul A. and Wang, Gufeng}, year={2018}, month={Sep}, pages={4606–4616} }
 @article{kumar_zoellner_maggard_wang_2018, title={Effect of doping Ge into Y2O3:Ho,Yb on the green-to-red emission ratio and temperature sensing}, volume={47}, ISSN={["1477-9234"]}, DOI={10.1039/c8dt02216j}, abstractNote={A series of Ge-doped monophase Y2O3:Ho,Yb phosphor materials has been synthesized using solid state reactions. The addition of Ge to the Y2O3 host decreases the Ho green emission (5F4/5S2 → 5I8) and increases the red emission (5F5 → 5I8), providing a new means to tune the green-to-red emission intensity ratio. It is proposed that the Ge-induced multiphonon relaxation process enhances the transition from the intermediate state 5I6 to 5I7, which tunes the green and red emission intensities. Most importantly, with the addition of Ge, the non-thermally coupled Ho green and red emitting levels are associated together, and the red-to-green emission intensity ratio becomes sensitive to environmental temperature change. The absolute thermal sensitivity is enhanced by a factor of >5 times that in the absence of Ge. The matched green and red emission intensities, as well as the high thermal sensitivity, make Y2O3:Ho,Yb,Ge an ideal probe for optical temperature sensing at the single particle level in live biological samples. This study demonstrates a new mechanism to channel non-thermally coupled energy levels to achieve high temperature sensitivity.}, number={32}, journal={DALTON TRANSACTIONS}, author={Kumar, Vineet and Zoellner, Brandon and Maggard, Paul A. and Wang, Gufeng}, year={2018}, month={Aug}, pages={11158–11165} }
 @article{hou_powel_dougherty_sommer_maggard_2018, title={Tunable Optical and Photocatalytic Properties of Low-Dimensional Copper(I)-Iodide Hybrids Using Coordinating Organic Ligands}, volume={18}, ISSN={["1528-7505"]}, DOI={10.1021/acs.cgd.8b00788}, abstractNote={A family of copper(I)-iodide/organic hybrid compounds was investigated for the impact of coordinating organic ligands on their structures, as well as on their optical and photocatalytic properties. This included the synthesis of two new crystalline compounds, [(CuI)2(bpmd)] and [(CuI)2(bpp)] (bpmd = 2,2′-bipyrimidine, bpp = 2,3-bis(2-pyridyl)pyrazine), both of which consist of chain structures formed by (CuI)2 rhombus-shaped dimers that are further coordinated to the N-groups of the bridging organic ligands. To more broadly investigate structure–property relationships within this system, nine related copper(I)-iodide/organic hybrid compounds, that is, [(CuI)2Ln] (n = 1 or 2; L = 1,2-bis(4-pyridyl) ethylene (bpe); 2,2′-bipyrimidine (bpmd); 2,3-bis(2-pyridyl) pyrazine (bpp); 4,4′-bipyridine (44bpy); pyridazine (pdz); pyrimidine (pmd); pyrazine (pz); pyrazinamide (pza); quinoxaline (quin)) were also prepared in high purity containing extended (CuI)∞ chains or sheets coordinated to bridging or terminating org...}, number={9}, journal={CRYSTAL GROWTH & DESIGN}, author={Hou, Feier and Powel, Matthew and Dougherty, Daniel B. and Sommer, Roger D. and Maggard, Paul A.}, year={2018}, month={Sep}, pages={5406–5416} }
 @article{zoellner_gordon_maggard_2017, title={A small bandgap semiconductor, p-type MnV2O6, active for photocatalytic hydrogen and oxygen production}, volume={46}, ISSN={["1477-9234"]}, DOI={10.1039/c7dt00780a}, abstractNote={Extensive research has been conducted with the goal to find a single bandgap material that can absorb visible light and efficiently drive the catalysis of water to both hydrogen and oxygen. The p-type MnV2O6 (C2/m, Z = 2, a = 9.289 Å, b = 3.535 Å, and c = 6.763 Å, β = 112.64°), synthesized via solid-state techniques, was investigated for its potential use in the visible-light photocatalysis of water. Mott-Schottky analysis was used to experimentally determine the energetic positions of the valence and conduction bands as +0.985 V and -0.464 V, respectively, at pH 5.68 vs. RHE. These are found to be suitable potentials to drive the reduction and oxidation of water under irradiation. The bandgap transitions, probed using spin-polarized density functional calculations, consist of the excitation of electrons from the half-filled Mn 3d5 orbitals to the empty V 3d0 orbitals. Both hydrogen and oxygen gas were observed as products during suspended-particle photocatalysis experiments under visible-light irradiation. The rate and total moles of gas produced were found to increase with the reaction temperature. As the temperature was raised from 30 °C to 37 °C and 44 °C, the moles of hydrogen produced over 6 hours increased by ∼1.5 and ∼2.5 times. Only oxygen is produced in pure water, showing that methanol is needed to drive hydrogen production.}, number={32}, journal={DALTON TRANSACTIONS}, author={Zoellner, Brandon and Gordon, Elijah and Maggard, Paul A.}, year={2017}, month={Aug}, pages={10657–10664} }
 @article{ortiz_zoellner_hong_jo_wang_liu_maggard_wang_2017, title={Harnessing Hot Electrons from Near IR Light for Hydrogen Production Using Pt-End-Capped-AuNRs}, volume={9}, ISSN={["1944-8244"]}, DOI={10.1021/acsami.7b05064}, abstractNote={Gold nanorods show great potential in harvesting natural sunlight and generating hot charge carriers that can be employed to produce electrical or chemical energies. We show that photochemical reduction of Pt(IV) to Pt metal mainly takes place at the ends of gold nanorods (AuNRs), suggesting photon-induced hot electrons are localized in a time-averaged manner at AuNR ends. To use these hot electrons efficiently, a novel synthetic method to selectively overgrow Pt at the ends of AuNRs has been developed. These Pt-end-capped AuNRs show relatively high activity for the production of hydrogen gas using artificial white light, natural sunlight, and more importantly, near IR light at 976 nm. Tuning of the surface plasmon resonance (SPR) wavelength of AuNRs changes the hydrogen gas production rate, indicating that SPR is involved in hot electron generation and photoreduction of hydrogen ions. This study shows that gold nanorods are excellent for converting low-energy photons into high-energy hot electrons, which can be used to drive chemical reactions at their surfaces.}, number={31}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Ortiz, Nathalia and Zoellner, Brandon and Hong, Soung Joung and Jo, Yue and Wang, Tao and Liu, Yang and Maggard, Paul A. and Wang, Gufeng}, year={2017}, month={Aug}, pages={25962–25969} }
 @article{king_boltersdorf_maggard_wong-ng_2017, title={Polymorphism and Structural Distortions of Mixed-Metal Oxide Photocatalysts Constructed with α-U3O8 Types of Layers}, volume={7}, ISSN={2073-4352}, url={http://dx.doi.org/10.3390/cryst7050145}, DOI={10.3390/cryst7050145}, abstractNote={A series of mixed-metal oxide structures based on the stacking of α-U3O8 type pentagonal bipyramid layers have been investigated for symmetry lowering distortions and photocatalytic activity. The family of structures contains the general composition Am+((n+1)/m)B(3n+1)O(8n+3) (e.g., A = Ag, Bi, Ca, Cu, Ce, Dy, Eu, Gd K, La, Nd, Pb, Pr, Sr, Y; B = Nb, Ta; m = 1–3; n = 1, 1.5, 2), and the edge-shared BO7 pentagonal pyramid single, double, and/or triple layers are differentiated by the average thickness, (i.e., 1 ≤ n ≤ 2), of the BO7 layers and the local coordination environment of the “A” site cations. Temperature dependent polymorphism has been investigated for structures containing single layered (n = 1) monovalent (m = 1) “A” site cations (e.g., Ag2Nb4O11, Na2Nb4O11, and Cu2Ta4O11). Furthermore, symmetry lowering distortions were observed for the Pb ion-exchange synthesis of Ag2Ta4O11 to yield PbTa4O11. Several members within the subset of the family have been constructed with optical and electronic properties that are suitable for the conversion of solar energy to chemical fuels via water splitting.}, number={5}, journal={Crystals}, publisher={MDPI AG}, author={King, Nacole and Boltersdorf, Jonathan and Maggard, Paul and Wong-Ng, Winnie}, year={2017}, month={May}, pages={145} }
 @misc{king_boltersdorf_maggard_wong-ng_2017, title={Polymorphism and structural distortions of mixed-metal oxide photocatalysts constructed with alpha-U3O8 types of layers}, volume={7}, number={5}, journal={Crystals}, author={King, N. and Boltersdorf, J. and Maggard, P. A. and Wong-Ng, W.}, year={2017} }
 @article{hewitt_boltersdorf_maggard_dougherty_2017, title={Recovery of of the bulk-like electronic structure of manganese phthalocyanine beyond the first monolayer on Bi2Te3}, volume={662}, ISSN={["1879-2758"]}, DOI={10.1016/j.susc.2017.03.014}, abstractNote={The evolution of electronic structure of manganese phthalocyanine on Bi2Te3 shows a transition to a bulk-like aspect abruptly after completion of the first layer. This allows the inference that, in the first layer, there is charge transfer and electronic hybridization involving the occupied Mn-derived d orbitals of the molecule into the conduction band of the substrate. The charge transfer coupling is seen using angle-resolved ultraviolet photoelectron spectroscopy by monitoring the evolution of work function and band structure with increasing molecular film thickness. The electronic structure in the second layer is more bulk-like as indicated by the reappearance of well-known low energy d orbitals that were depopulated in the first layer. Scanning tunneling microscopy shows that the transition to bulk like behavior is also reflected in film structure as a transition from a unique disordered monolayer to a locally ordered and dense second layer. These observations are relevant to ongoing efforts to control topological insulator interfaces especially for spintronics applications.}, journal={SURFACE SCIENCE}, author={Hewitt, A. S. and Boltersdorf, J. and Maggard, P. A. and Dougherty, D. B.}, year={2017}, month={Aug}, pages={87–92} }
 @misc{sullivan_zoellner_maggard_2016, title={Copper(I)-Based p-Type Oxides for Photoelectrochemical and Photovoltaic Solar Energy Conversion}, volume={28}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.6b00926}, abstractNote={Recent research efforts have been growing into p-type copper(I) based oxides for development of their use in solar energy applications. The oxides of interest include the binary Cu2O and a number of new ternary CuxMyOz oxides. Both the binary and ternary Cu(I)-based oxides have many advantages when compared to other well-known p-type oxides such as NiO, III–V, and II–VI semiconductors. The benefits found within the diverse group of Cu(I)-containing oxides include bandgap sizes that can be tuned from ∼1.2 to >3.0 eV, high charge carrier mobility, and favorable band energies relative to fuel-producing redox couples. These properties give them potential utility in a variety of different solar applications, such as in dye-sensitized solar cells and suspended powder photocatalysis. Research efforts into surface modifications and changes in their chemical compositions and structures have allowed for greater stability and greater efficiency in aqueous solutions, both of which have represented two key barriers fo...}, number={17}, journal={CHEMISTRY OF MATERIALS}, author={Sullivan, Ian and Zoellner, Brandon and Maggard, Paul A.}, year={2016}, month={Sep}, pages={5999–6016} }
 @article{zoellner_stuart_chung_dougherty_jones_maggard_2016, title={CuNb1−xTaxO3 (x ≤ 0.25) solid solutions: impact of Ta(v) substitution and Cu(i) deficiency on their structure, photocatalytic, and photoelectrochemical properties}, volume={4}, ISSN={2050-7488 2050-7496}, url={http://dx.doi.org/10.1039/c5ta06609c}, DOI={10.1039/c5ta06609c}, abstractNote={Solid solutions of Cu(I)-containing oxide p-type semiconductors provide key opportunities to probe the fundamental relationships between chemical compositions and crystal structures, bandgap sizes, band energies, and photoelectrochemical properties. Members of the CuNb1−xTaxO3 (0 < x ≤ 0.25) solid solution have been synthesized via high temperature solid-state methods. The structure of CuNbO3 was found to be Cu-deficient Cu0.965NbO3 after heating in air at 250 °C for 3 hours, i.e., under similar conditions as those used to prepare it as a polycrystalline film. Powder X-ray diffraction techniques confirmed the purity of each composition up to x ≤ 0.25 and the lattice parameters were refined as the molar ratio of Nb(V) and Ta(V) was varied (a = 9.499 to 9.506 A, b = 8.439 to 8.451 A, c = 6.768 to 6.781 A and β = 90.847 to 90.694°). An increase in the amount of Ta(V) yielded a small blue shift of the bandgap size from ∼1.89 eV to ∼1.97 eV for CuNb1−xTaxO3 from x = 0 to 0.25. Polycrystalline films of each member of the CuNb1−xTaxO3 solid solutions produced relatively comparable p-type photocurrents of up to −0.5 mA cm−2, while the stability of the cathodic photocurrent also remained similar with increasing Ta(V) content. Mott–Schottky analysis of CuNb1−xTaxO3 showed that the conduction band edge of −1.5 (vs. SHE) provides a sufficient overpotential (∼800 mV) to drive the reduction of water to hydrogen gas at the surface. The capability of the solid solutions to drive hydrogen production was confirmed through suspended particle photocatalysis. Further characterization of the CuNb0.91Ta0.09O3 composition included scanning electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric analyses. These data show that Cu(I) is oxidized to Cu(II) as CuNb1−xTaxO3 is heated in air. Thus, the formation of Cu(II) rich regions at the surface, together with the Ta(V) content, are found to play important roles in the stability and magnitude of the cathodic photocurrents produced under visible-light irradiation. Importantly, these results demonstrate that solid solution compositions can be used in films for solar energy conversion, notwithstanding their inherent atomic disorder.}, number={8}, journal={Journal of Materials Chemistry A}, publisher={Royal Society of Chemistry (RSC)}, author={Zoellner, Brandon and Stuart, Sean and Chung, Ching-Chang and Dougherty, Daniel B. and Jones, Jacob L. and Maggard, Paul A.}, year={2016}, pages={3115–3126} }
 @article{boltersdorf_sullivan_shelton_wu_gray_zoellner_osterloh_maggard_2016, title={Flux Synthesis, Optical and Photocatalytic Properties of n-type Sn2TiO4: Hydrogen and Oxygen Evolution under Visible Light}, volume={28}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.6b02003}, abstractNote={The n-type Sn2TiO4 phase was synthesized using flux methods and found to have one of the smallest visible-light bandgap sizes known that also maintains suitable conduction and valence band energies for driving photocatalytic water-splitting reactions. The Sn2TiO4 phase was synthesized using either a SnCl2 flux or a SnCl2/SnF2 peritectic flux in a 2:1 flux-to-precursor ratio heated at 600 and 400 °C for 24 h, respectively. The two types of salt fluxes resulted in large rod-shaped particles at 600 °C and smaller tetragonal prism-shaped particles at 400 °C. Surface photovoltage spectroscopy measurements produced a negative photovoltage under illumination >1.50 eV, which confirmed electrons as the majority charge carriers and ∼1.50 eV as the effective band gap. Mott–Schottky measurements at pH 9.0 showed the conduction (−0.54 V vs NHE) and valence band (+1.01 V vs NHE) positions meet the critical thermodynamic requirements for total water splitting. The Sn2TiO4 particles were deposited and annealed as polycry...}, number={24}, journal={CHEMISTRY OF MATERIALS}, author={Boltersdorf, Jonathan and Sullivan, Ian and Shelton, Timothy L. and Wu, Zongkai and Gray, Matthew and Zoellner, Brandon and Osterloh, Frank E. and Maggard, Paul A.}, year={2016}, month={Dec}, pages={8876–8889} }
 @article{king_sullivan_watkins-curry_chan_maggard_2016, title={Flux-mediated syntheses, structural characterization and low-temperature polymorphism of the p-type semiconductor Cu2Ta4O11}, volume={236}, ISSN={["1095-726X"]}, DOI={10.1016/j.jssc.2015.08.041}, abstractNote={A new low-temperature polymorph of the copper(I)-tantalate, α-Cu2Ta4O11, has been synthesized in a molten CuCl-flux reaction at 665 °C for 1 h and characterized by powder X-ray diffraction Rietveld refinements (space group Cc (#9), a=10.734(1) Å, b=6.2506(3) Å, c=12.887(1) Å, β=106.070(4)°). The α-Cu2Ta4O11 phase is a lower-symmetry monoclinic polymorph of the rhombohedral Cu2Ta4O11 structure (i.e., β-Cu2Ta4O11 space group R3̅c (#167), a=6.2190(2) Å, c=37.107(1) Å), and related crystallographically by ahex=amono/√3, bhex=bmono, and chex=3cmonosinβmono. Its structure is similar to the rhombohedral β-Cu2Ta4O11 and is composed of single layers of highly-distorted and edge-shared TaO7 and TaO6 polyhedra alternating with layers of nearly linearly-coordinated Cu(I) cations and isolated TaO6 octahedra. Temperature dependent powder X-ray diffraction data show the α-Cu2Ta4O11 phase is relatively stable under vacuum at 223 K and 298 K, but reversibly transforms to β-Cu2Ta4O11 by at least 523 K and higher temperatures. The symmetry-lowering distortions from β-Cu2Ta4O11 to α-Cu2Ta4O11 arise from the out-of-center displacements of the Ta 5d0 cations in the TaO7 pentagonal bipyramids. The UV–vis diffuse reflectance spectrum of the monoclinic α-Cu2Ta4O11 shows an indirect bandgap transition of ∼2.6 eV, with the higher-energy direct transitions starting at ∼2.7 eV. Photoelectrochemical measurements on polycrystalline films of α-Cu2Ta4O11 show strong cathodic photocurrents of ∼1.5 mA/cm2 under AM 1.5 G solar irradiation.}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={King, Nacole and Sullivan, Ian and Watkins-Curry, Pilanda and Chan, Julia Y. and Maggard, Paul A.}, year={2016}, month={Apr}, pages={10–18} }
 @article{boltersdorf_zoellner_fancher_jones_maggard_2016, title={Single- and Double-Site Substitutions in Mixed-Metal Oxides: Adjusting the Band Edges Toward the Water Redox Couples}, volume={120}, ISSN={["1932-7455"]}, DOI={10.1021/acs.jpcc.6b05758}, abstractNote={New mixed-metal oxide solid solutions, i.e., the single-metal substituted Na2Ta4–yNbyO11 (0 ≤ y ≤ 4) and the double-metal substituted Na2–2xSnxTa4–yNbyO11 (0 ≤ y ≤ 4; 0 ≤ x ≤ 0.35), were investigated and used to probe the impact of composition on their crystalline structures, optical band gaps, band energies, and photocatalytic properties. The Na2Ta4O11 (y = 1) phase was prepared by flux-mediated synthesis, while the members of the Na2Ta4–yNbyO11 solid solution (1 ≤ y ≤ 4) were prepared by traditional high-temperature reactions. The Sn(II)-containing Na2–2xSnxTa4–yNbyO11 (0 ≤ y ≤ 4) solid solutions were prepared by flux-mediated ion-exchange reactions of the Na2Ta4–yNbyO11 solid solutions within a SnCl2 flux. The crystalline structures of both solid solutions are based on the parent Na2B4O11 (B = Nb, Ta) phases and consist of layers of edge-shared BO7 pentagonal bipyramids that alternate with layers of isolated BO6 octahedra surrounded by Na(I) cations. Rietveld refinements of the Na2Ta4–yNbyO11 solid sol...}, number={34}, journal={Journal of Physical Chemistry C}, author={Boltersdorf, J. and Zoellner, B. and Fancher, C. and Jones, J. and Maggard, P.A.}, year={2016}, month={Aug}, pages={19175–19188} }
 @article{luo_ou_smirnova_maggard_2016, title={Synthesis of New Mixed-Metal Ammonium Vanadates: Cation Order versus Disorder, and Optical and Photocatalytic Properties}, volume={16}, ISSN={["1528-7505"]}, DOI={10.1021/acs.cgd.6b00851}, abstractNote={Two new ammonium vanadate hydrates, i.e., M3(H2O)2V8O24·2NH4 (M = Mn and Co, I and II, respectively) were synthesized using hydrothermal reaction conditions, and their structures were determined by single crystal X-ray diffraction [I: P2/m (No. 10), Z = 1, a = 8.2011(2) A, b = 3.5207(1) A, c = 9.9129(3) A, β = 110.987(2)°; II: C2/m (No. 12), Z = 2, a = 19.4594(6) A, b = 6.7554(2) A, c = 8.4747(3) A, β = 112.098(2)°]. Interestingly, the two structures are homeotypic, with the structure of I exhibiting an uncommon type of structural disorder between locally-bridging Mn(H2O)22+ (i.e., part of the oxide framework) and nonbridging NH4+ cations over the same site (1:2 ratio), wherein two NH4+ ions occupy the same site as the two H2O molecules when Mn(II) is vacant. The amount of Mn(II) in the formula of I was determined by a combination of techniques, including electron paramagnetic resonance, while the relative amounts of NH4+/H2O in its structure were determined by combined thermogravimetric-mass spectrometry...}, number={10}, journal={CRYSTAL GROWTH & DESIGN}, author={Luo, Lan and Ou, Erkang and Smirnova, Tatyana I. and Maggard, Paul A.}, year={2016}, month={Oct}, pages={5762–5770} }
 @article{dufficy_luo_fedkiw_maggard_2016, title={Vacancy-induced manganese vanadates and their potential application to Li-ion batteries}, volume={52}, ISSN={["1364-548X"]}, DOI={10.1039/c6cc02249a}, abstractNote={We report on the synthesis and characterization of a novel manganese vanadate, Mn1.5(H2O)(NH4)V4O12, with rare in situ disorder of Mn(H2O)2(2+)/2NH4(+). We show that vacancies created by ammonium ions and coordinating water molecules within the manganese vanadate crystal structure yield high-charge capacity, favorable rate capability, and long cycle life in Li-ion half-cells.}, number={47}, journal={CHEMICAL COMMUNICATIONS}, author={Dufficy, Martin K. and Luo, Lan and Fedkiw, Peter S. and Maggard, Paul A.}, year={2016}, pages={7509–7512} }
 @article{skorupska_maggard_eichberger_schwarzburg_shahbazi_zoellner_parkinson_2015, title={Combinatorial Investigations of High Temperature CuNb Oxide Phases for Photoelectrochemical Water Splitting}, volume={17}, ISSN={["2156-8944"]}, DOI={10.1021/acscombsci.5b00142}, abstractNote={High-throughput combinatorial methods have been useful in identifying new oxide semiconductors with the potential to be applied to solar water splitting. Most of these techniques have been limited to producing and screening oxide phases formed at temperatures below approximately 550 °C. We report the development of a combinatorial approach to discover and optimize high temperature phases for photoelectrochemical water splitting. As a demonstration material, we chose to produce thin films of high temperature CuNb oxide phases by inkjet printing on two different substrates: fluorine-doped tin oxide and crystalline Si, which required different sample pyrolysis procedures. The selection of pyrolysis parameters, such as temperature/time programs, and the use of oxidizing, nonreactive or reducing atmospheres determines the composition of the thin film materials and their photoelectrochemical performance. XPS, XRD, and SEM analyses were used to determine the composition and oxidation states within the copper niobium oxide phases and to then guide the production of target Cu(1+)Nb(5+)-oxide phases. The charge carrier dynamics of the thin films produced by the inkjet printing are compared with pure CuNbO3 microcrystalline material obtained from inorganic bulk synthesis.}, number={12}, journal={ACS COMBINATORIAL SCIENCE}, author={Skorupska, Katarzyna and Maggard, Paul A. and Eichberger, Rainer and Schwarzburg, Klaus and Shahbazi, Paria and Zoellner, Brandon and Parkinson, Bruce A.}, year={2015}, month={Dec}, pages={742–751} }
 @article{boltersdorf_king_maggard_2015, title={Flux-mediated crystal growth of metal oxides: synthetic tunability of particle morphologies, sizes, and surface features for photocatalysis research}, volume={17}, ISSN={["1466-8033"]}, DOI={10.1039/c4ce01587h}, abstractNote={Molten-salt reactions can be used to prepare single-crystal metal-oxide particles with morphologies and sizes that can be varied from the nanoscale to the microscale, subsequently enabling a growing number of novel investigations into their photocatalytic activities. Crystal growth using flux-mediated methods facilitates finer synthetic manipulation over particle characteristics. The synthetic flexibility that flux synthesis affords for the growth of metal-oxides has led to the stabilization of phases with limited stability, the discovery of new compositions, and access to alternate crystal morphologies and sizes that exhibit significant changes in photocatalytic activities at their surfaces, such as for the reduction of water to hydrogen in aqueous solutions. This approach has significantly impacted the current understanding of the optical and photocatalytic properties of metal-oxides, such as the dependence of band gap energies on the structure and chemical composition (i.e., obtained from flux-mediated ion-exchange reactions). Thus, flux preparations of metal-oxide photocatalysts assist in the growth and optimization of their particles in order to understand and tune the photocatalytic reaction rates at their surfaces.}, number={11}, journal={CRYSTENGCOMM}, author={Boltersdorf, Jonathan and King, Nacole and Maggard, Paul A.}, year={2015}, pages={2225–2241} }
 @article{luo_zeng_li_luo_smirnova_maggard_2015, title={Manganese-Vanadate Hybrids: Impact of Organic Ligands on Their Structures, Thermal Stabilities, Optical Properties, and Photocatalytic Activities}, volume={54}, ISSN={["1520-510X"]}, DOI={10.1021/acs.inorgchem.5b00931}, abstractNote={Manganese(II)-vanadate(V)/organic hybrids were prepared in high purity using four different N-donor organic ligands (2,6:2',2″-terpyridine = terpy, 2,2'-bipyrimidine = bpym, o-phenanthroline = o-phen, and 4,4'-bipyridine = 4,4'-bpy), and their crystalline structures, thermal stabilities, optical properties, photocatalytic activities and electronic structures were investigated as a function of the organic ligand. Hydrothermal reactions were employed that targeted a 1:2 molar ratio of Mn(II)/V(V), yielding four hybrid solids with the compositions of Mn(terpy)V2O6·H2O (I), Mn2(bpym)V4O12·0.6H2O (II), Mn(H2O)(o-phen)V2O6 (III), and Mn(4,4'-bpy)V2O6·1.16H2O (IV). The inorganic component within these hybrid compounds, that is, [MnV2O6], forms infinite chains in I and layers in II, III, and IV. In each case, the organic ligand preferentially coordinates to the Mn(II) cations within their respective structures, either as chelating and three-coordinate (mer isomer in I) or two-coordinate (cis isomers in II and III), or as bridging and two coordinate (trans isomer in IV). The terminating ligands in I (terpy) and III (o-phen) yield nonbridged "MnV2O6" chains and layers, respectively, while the bridging ligands in II (bpym) and IV (4,4'-bpy) result in three-dimensional, pillared hybrid networks. The coordination number of the ligand, that is, two- or three-coordinate, has the predominant effect on the dimensionality of the inorganic component, while the connectivity of the combined metal-oxide/organic network is determined by the chelating versus bridging ligand coordination modes. Each hybrid compound decomposes into crystalline MnV2O6 upon heating in air with specific surface areas from ∼7 m(2)/g for III to ∼41 m(2)/g for IV, depending on the extent of structural collapse as the lattice water is removed. All hybrid compounds exhibit visible-light bandgap sizes from ∼1.7 to ∼2.0 eV, decreasing with the increased dimensionality of the [MnV2O6] network in the order of I > II ≈ III > IV. These bandgap sizes are smaller by ∼0.1-0.4 eV in comparison to related vanadate hybrids, owing to the addition of the higher-energy 3d orbital contributions from the Mn(II) cations. Each compound also exhibits temperature-dependent photocatalytic activities for hydrogen production under visible-light irradiation in 20% methanol solutions, with threshold temperatures of ∼30 °C for III, ∼36 °C for I, and ∼40 °C for II, IV, and V4O10(o-phen)2. Hydrogen production rates are ∼142 μmol H2 g(-1)·h(-1), ∼673 μmol H2 g(-1)·h(-1), ∼91 μmol H2 g(-1)·h(-1), and ∼218 μmol H2 g(-1)·h(-1) at 40 °C, for I, II, III, and IV, respectively, increasing with the oxide/organic network connectivity. In contrast, the related V4O10(o-phen)2 exhibits a much lower photocatalytic rate of ∼36 H2 g(-1)·h(-1). Electronic structure calculations based on density-functional theory methods show that the valence band edges are primarily derived from the half-filled Mn 3d(5) orbitals in each, while the conduction band edges are primarily comprised of contributions from the empty V 3d(0) orbitals in I and II and from ligand π* orbitals in III. Thus, the coordinating organic ligands are shown to significantly affect the local and extended structural features, which has elucidated the underlying relationships to their photocatalytic activities, visible-light bandgap sizes, electronic structures, and thermal stabilities.}, number={15}, journal={INORGANIC CHEMISTRY}, author={Luo, Lan and Zeng, Yuhan and Li, Le and Luo, Zhixiang and Smirnova, Tatyana I. and Maggard, Paul A.}, year={2015}, month={Aug}, pages={7388–7401} }
 @article{sahoo_zoellner_maggard_2015, title={Optical, electronic, and photoelectrochemical properties of the p-type Cu3-xVO4 semiconductor}, volume={3}, ISSN={["2050-7496"]}, DOI={10.1039/c4ta04876h}, abstractNote={Investigations into new p-type metal oxides with small bandgap sizes, i.e., Eg ∼0.9 eV to ∼1.5 eV, are currently needed to enable the preparation of tandem cells with high solar-to-hydrogen conversion efficiencies. The p-type Cu(I)-vanadate, Cu3VO4 (space group I2m (no. 121), Z = 2, a = 4.581(4) A, c = 8.998(2) A), was synthesized in high purity using solid-state methods and investigated for its small optical bandgap size (Eg ∼ 1.2 eV) and photoelectrochemical properties in the form of polycrystalline films. Powder X-ray diffraction and electron microscopy data show that, beginning at 300 °C in air, a Cu-deficient composition is formed according to: Cu3VO4(s) + (x/2) O2(g) → Cu3−xVO4(s) + x CuO(s). At 350 °C the compound decomposes at the surfaces into the Cu(II)-containing oxides CuO and Cu3V2O8 (3 : 1 molar ratio), the latter protruding as rods (i.e., ∼15–25 nm in width by ∼1–5 μm in length) from the particles' surfaces. Polycrystalline films of p-type Cu3VO4 were prepared under these conditions (i.e., heated in air at 300 °C or 350 °C) and found to yield significant cathodic photocurrents under solar-simulated, visible-light irradiation (λ > 420 nm; AM 1.5 G filter, irradiant power density of ∼100 mW cm−2). Their photocurrents increased with the heating temperature of the film and with the applied bias, e.g., ∼0.1 mA cm−2 at zero applied bias to ∼0.25 mA cm−2 at −0.2 applied bias (pH = 5.8). The photocurrent of a non-heated film was negligible compared to the films heated in air and exhibited a larger dark current. Further, when CuO nanoparticles were formed directly onto the Cu3VO4 films from aqueous Cu(NO3)2 solutions (i.e., 0.1 M and 0.25 M), cathodic photocurrents of ∼0.2 mA cm−2 are similarly found. Mott–Schottky measurements determined the energetic potential of the Cu3VO4 conduction band to be at ∼−0.63 V versus RHE at pH = 5.8, with an acceptor concentration of ∼1.29 × 1017 cm−3. Thus, a type-II band offset is predicted to occur between the p-type Cu3VO4 film and the p-type CuO surface nanoparticles, and elucidating the critical role of the CuO surface nanoparticles in forming a charge rectification barrier and enhancing the charge separation at the surfaces. Electronic structure calculations show that the conduction band states of Cu3VO4 are delocalized within the ab-plane of the structure and exhibit an ∼2 eV band dispersion centered around the gamma k-point. The bandgap size, conduction band dispersion, and band energies of Cu3VO4 are thus found to be promising for further investigations into tandem n-/p-type photoelectrochemical cells for solar energy conversion applications.}, number={8}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Sahoo, Prangya P. and Zoellner, Brandon and Maggard, Paul A.}, year={2015}, pages={4501–4509} }
 @article{sullivan_brown_llansola-portoles_gervaldo_kodis_moore_gust_moore_maggard_2015, title={Photoinjection of High Potential Holes into Cu5Ta11O30 Nanoparticles by Porphyrin Dyes}, volume={119}, ISSN={["1932-7447"]}, DOI={10.1021/acs.jpcc.5b02174}, abstractNote={Excited-state hole injection into the valence band of Cu5Ta11O30 nanoparticles (NP-Cu5Ta11O30) was investigated through sensitization with zinc porphyrin dyes using simulated solar irradiance. The Cu5Ta11O30 nanoparticles were prepared by a flux-mediated synthesis and found to have an average particle size of ∼10–15 nm by DLS and TEM. The zinc 4-(10,15,20-tris(4-pyridinyl)-porphin-5-yl)phenylphosphonic acid (D1) and its analogue, in which the pyridine groups are methylated (D2), were synthesized and found to have excited-state reduction potentials appropriate for p-type dye sensitization of the nanoparticles. The dye-sensitized NP-Cu5Ta11O30 exhibited fluorescence quenching consistent with electron transfer from the NP-Cu5Ta11O30 to the dye; forward and recombination rates were obtained by transient absorption measurements. Hole injection times of 8 ps and <100 fs were observed for D1 and D2, respectively. Nanoparticulate films of Cu5Ta11O30 were prepared and evaluated in dye-sensitized solar cells under ...}, number={37}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Sullivan, Ian and Brown, Chelsea L. and Llansola-Portoles, Manuel J. and Gervaldo, Miguel and Kodis, Gerdenis and Moore, Thomas A. and Gust, Devens and Moore, Ana L. and Maggard, Paul A.}, year={2015}, month={Sep}, pages={21294–21303} }
 @article{boltersdorf_maggard_2015, title={Structural and electronic investigations of PbTa4O11 and BiTa7O19 constructed from alpha-U3O8 types of layers}, volume={229}, ISSN={["1095-726X"]}, DOI={10.1016/j.jssc.2015.06.019}, abstractNote={The PbTa4O11 and BiTa7O19 phases were prepared by ion-exchange and solid-state methods, respectively, and their structures were characterized by neutron time-of-flight diffraction and Rietveld refinement methods (PbTa4O11, R3 (No. 146), a=6.23700(2) Å, c=36.8613(1) Å; BiTa7O19, P6¯c2 (No. 188), a=6.2197(2) Å, c=20.02981(9) Å). Their structures are comprised of layers of TaO6 octahedra surrounded by three 7-coordinate Pb(II) cations or two 8-coordinate Bi(III) cations. These layers alternate down the c-axis with α-U3O8 types of single and double TaO7 pentagonal bipyramid layers. In contrast to earlier studies, both phases are found to crystallize in noncentrosymmetric structures. Symmetry-lowering structural distortions within PbTa4O11, i.e. R3¯c→R3, are found to be a result of the displacement of the Ta atoms within the TaO7 and TaO6 polyhedra, towards the apical and facial oxygen atoms, respectively. In BiTa7O19, relatively lower reaction temperatures leads to an ordering of the Bi/Ta cations within a lower-symmetry structure, i.e., P63/mcm→P6¯c2. In the absence of Bi/Ta site disorder, the Ta–O–Ta bond angles decrease and the Ta–O bond distances increase within the TaO7 double layers. Scanning electron microscopy images reveal two particle morphologies for PbTa4O11, hexagonal rods and finer irregularly-shaped particles, while BiTa7O19 forms as aggregates of irregularly-shaped particles. Electronic-structure calculations confirm the highest-energy valence band states are comprised of O 2p-orbitals and the respective Pb 6s-orbital and Bi 6s-orbital contributions. The lowest-energy conduction band states are composed of Ta 5d-orbital contributions that are delocalized over the TaO6 octahedra and layers of TaO7 pentagonal bipyramids. The symmetry-lowering distortions in the PbTa4O11 structure, and the resulting effects on its electronic structure, lead to its relatively higher photocatalytic activity compared to similar structures without these distortions.}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Boltersdorf, Jonathan and Maggard, Paul A.}, year={2015}, month={Sep}, pages={310–321} }
 @article{carpenter_scholle_sadeghifar_francis_boltersdorf_weare_argyropoulos_maggard_ghiladi_2015, title={Synthesis, Characterization, and Antimicrobial Efficacy of Photomicrobicidal Cellulose Paper}, volume={16}, ISSN={["1526-4602"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84938937944&partnerID=MN8TOARS}, DOI={10.1021/acs.biomac.5b00758}, abstractNote={Toward our goal of scalable, antimicrobial materials based on photodynamic inactivation, paper sheets comprised of photosensitizer-conjugated cellulose fibers were prepared using porphyrin and BODIPY photosensitizers, and characterized by spectroscopic (infrared, UV-vis diffuse reflectance, inductively coupled plasma optical emission) and physical (gel permeation chromatography, elemental, and thermal gravimetric analyses) methods. Antibacterial efficacy was evaluated against Staphylococcus aureus (ATCC-2913), vancomycin-resistant Enterococcus faecium (ATCC-2320), Acinetobacter baumannii (ATCC-19606), Pseudomonas aeruginosa (ATCC-9027), and Klebsiella pneumoniae (ATCC-2146). Our best results were achieved with a cationic porphyrin-paper conjugate, Por((+))-paper, with inactivation upon illumination (30 min, 65 ± 5 mW/cm(2), 400-700 nm) of all bacterial strains studied by 99.99+% (4 log units), regardless of taxonomic classification. Por((+))-paper also inactivated dengue-1 virus (>99.995%), influenza A (∼ 99.5%), and human adenovirus-5 (∼ 99%). These results demonstrate the potential of cellulose materials to serve as scalable scaffolds for anti-infective or self-sterilizing materials against both bacteria and viruses when employing a photodynamic inactivation mode of action.}, number={8}, journal={BIOMACROMOLECULES}, author={Carpenter, Bradley L. and Scholle, Frank and Sadeghifar, Hasan and Francis, Aaron J. and Boltersdorf, Jonathan and Weare, Walter W. and Argyropoulos, Dimitris S. and Maggard, Paul A. and Ghiladi, Reza A.}, year={2015}, month={Aug}, pages={2482–2492} }
 @article{king_sommer_watkins-curry_chan_maggard_2015, title={Synthesis, Structure, and Thermal Instability of the Cu2Ta4O11 Phase}, volume={15}, ISSN={["1528-7505"]}, DOI={10.1021/cg500987c}, abstractNote={The Cu(I)-tantalate, Cu2Ta4O11, has been synthesized by flux methods in high purity and characterized by single-crystal X-ray diffraction (space group R3c (167), a = 6.219(2) A, c = 37.107(1) A). The compound is a new n = 1 member of the Cu(I)-tantalate CuxTa3n+1O8n+3 series of structures and can be prepared in a molten CuCl flux within a relatively low temperature range of ∼625–700 °C, in comparison to the synthesis of Cu5Ta11O30 (n = 1.5) and Cu3Ta7O19 (n = 2) at ∼800 to 1000 °C. The structure consists of layers of TaO7 pentagonal bipyramids that alternate with layers of isolated TaO6 octahedra and linearly coordinated Cu(I) cations. An increasing Cu-site vacancy across this series from Cu3Ta7O19 (100%), to Cu5Ta11O30 (83.3%), to Cu2Ta4O11 (66.7%) leads to an increasing fraction of O atoms that are not locally charge balanced by the Ta(V)/Cu(I) cations and thus yields decreased stability of Cu2Ta4O11. Thermal analysis shows that Cu2Ta4O11 decomposes in air or under flowing nitrogen at temperatures abov...}, number={2}, journal={CRYSTAL GROWTH & DESIGN}, publisher={American Chemical Society (ACS)}, author={King, Nacole and Sommer, Roger D. and Watkins-Curry, Pilanda and Chan, Julia Y. and Maggard, Paul A.}, year={2015}, month={Feb}, pages={552–558} }
 @article{hewitt_wang_boltersdorf_maggard_dougherty_2014, title={Coexisting Bi and Se surface terminations of cleaved Bi2Se3 single crystals}, volume={32}, number={4}, journal={Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures}, author={Hewitt, A. S. and Wang, J. Y. and Boltersdorf, J. and Maggard, P. A. and Dougherty, D. B.}, year={2014} }
 @article{king_sahoo_fuoco_stuart_dougherty_liu_maggard_2014, title={Copper Deficiency in the p-Type Semiconductor Cu1–xNb3O8}, volume={26}, ISSN={0897-4756 1520-5002}, url={http://dx.doi.org/10.1021/CM404147J}, DOI={10.1021/cm404147j}, abstractNote={The p-type semiconductor CuNb3O8 has been synthesized by solid-state and flux reactions and investigated for the effects of copper extrusion from its structure at 250–750 °C in air. High purity CuNb3O8 could be prepared by solid-state reactions at 750 °C at reaction times of 15 min and 48 h, and within a CuCl flux (10:1 molar ratio) at 750 °C at reaction times of 15 min and 12 h. The CuNb3O8 phase grows rapidly into well-faceted micrometer-sized crystals under these conditions, even with the use of Cu2O and Nb2O5 nanoparticle reactants. Heating CuNb3O8 in air to 450 °C for 3 h yields Cu-deficient Cu0.79(2)Nb3O8 that was characterized by powder X-ray Rietveld refinements (Sp. Grp. P21/a, Z = 4, a = 15.322(2) A, b = 5.0476(6) A, c = 7.4930(6) A, β = 107.07(1)o, and V = 554.0(1) A3). The parent structure of CuNb3O8 is maintained with ∼21% copper vacancies but with notably shorter Cu–O distances (by 0.16–0.27 A) within the Cu–O–Nb1 zigzag chains down its b-axis. Copper is extruded at high temperatures in air ...}, number={6}, journal={Chemistry of Materials}, publisher={American Chemical Society (ACS)}, author={King, Nacole and Sahoo, Prangya Parimita and Fuoco, Lindsay and Stuart, Sean and Dougherty, Daniel and Liu, Yi and Maggard, Paul A.}, year={2014}, month={Mar}, pages={2095–2104} }
 @article{luo_lin_li_smirnova_maggard_2014, title={Copper-Organic/Octamolybdates: Structures, Bandgap Sizes, and Photocatalytic Activities}, volume={53}, ISSN={0020-1669 1520-510X}, url={http://dx.doi.org/10.1021/IC402910A}, DOI={10.1021/ic402910a}, abstractNote={The structures, optical bandgap sizes, and photocatalytic activities are described for three copper-octamolybdate hybrid solids prepared using hydrothermal methods, [Cu(pda)]4[β-Mo8O26] (I; pda = pyridazine), [Cu(en)2]2[γ-Mo8O26] (II; en = ethylenediamine), and [Cu(o-phen)2]2[α-Mo8O26] (III; o-phen = o-phenanthroline). The structure of I consists of a [Cu(pda)]4(4+) tetramer that bridges to neighboring [β-Mo8O26](4-) octamolybdate clusters to form two-dimensional layers that stack along the a axis. The previously reported structures of II and III are constructed from [Cu2(en)4Mo8O26] and [Cu2(o-phen)4Mo8O26] clusters. The optical bandgap sizes were measured by UV-vis diffuse reflectance techniques to be ∼1.8 eV for I, ∼3.1 eV for II, and ∼3.0 eV for III. Electronic structure calculations show that the smaller bandgap size of I originates primarily from an electronic transition between the valence and conduction band edges comprised of filled 3d(10) orbitals on Cu(I) and empty 4d(0) orbitals on Mo(VI). Both II and III contain Cu(II) and exhibit larger bandgap sizes. Accordingly, aqueous suspensions of I exhibit visible-light photocatalytic activity for the production of oxygen at a rate of ∼90 μmol O2 g(-1) h(-1) (10 mg samples; radiant power density of ∼1 W/cm(2)) and a turnover frequency per calculated surface [Mo8O26](4-) cluster of ∼36 h(-1). Under combined ultraviolet and visible-light irradiation, I also exhibits photocatalytic activity for hydrogen production in 20% aqueous methanol of ∼316 μmol H2 g(-1) h(-1). By contrast, II decomposed during the photocatalysis measurements. The molecular [Cu2(o-phen)4(α-Mo8O26)] clusters of III dissolve into the aqueous methanol solution under ultraviolet irradiation and exhibit homogeneous photocatalytic rates for hydrogen production of up to ∼8670 μmol H2·g(-1) h(-1) and a turnover frequency of 17 h(-1). The clusters of III can be precipitated out by evaporation and redispersed into solution with no apparent decrease in photocatalytic activity. During the photocatalysis measurements, the dissolution of the clusters in III is found to occur with the reduction of Cu(II) to Cu(I), followed by subsequent detachment from the octamolybdate cluster. The lower turnover frequency, but higher photocatalytic rate, of III arises from the net contribution of all dissolved [Cu2(o-phen)4(α-Mo8O26)] clusters, compared to only the surface clusters for the heterogeneous photocatalysis of I.}, number={7}, journal={Inorganic Chemistry}, publisher={American Chemical Society (ACS)}, author={Luo, Lan and Lin, Haisheng and Li, Le and Smirnova, Tatyana I. and Maggard, Paul A.}, year={2014}, month={Mar}, pages={3464–3470} }
 @article{sullivan_sahoo_fuoco_hewitt_stuart_dougherty_maggard_2014, title={Cu-Deficiency in the p-Type Semiconductor Cu5–xTa11O30: Impact on Its Crystalline Structure, Surfaces, and Photoelectrochemical Properties}, volume={26}, ISSN={0897-4756 1520-5002}, url={http://dx.doi.org/10.1021/CM502891T}, DOI={10.1021/cm502891t}, abstractNote={The p-type semiconductor Cu5Ta11O30 has been investigated for the effect of Cu extrusion on its crystalline structure, surface chemistry, and photoelectrochemical properties. The Cu5Ta11O30 phase was prepared in high purity using a CuCl-mediated flux synthesis route, followed by heating the products in air from 250 to 750 °C in order to investigate the effects of its reported film preparation conditions as a p-type photoelectrode. At 650 °C and higher temperatures, Cu5Ta11O30 is found to decompose into CuTa2O6 and Ta2O5. At lower temperatures of 250 to 550 °C, nanosized CuIIO surface islands and a Cu-deficient Cu5–xTa11O30 crystalline structure (i.e., x ∼ 1.8(1) after 450 °C for 3 h in air) is found by electron microscopy and Rietveld structural refinement results, respectively. Its crystalline structure exhibits a decrease in the unit cell volume with increasing reaction temperature and time, owing to the increasing removal of Cu(I) ions from its structure. The parent structure of Cu5Ta11O30 is conserved...}, number={23}, journal={Chemistry of Materials}, publisher={American Chemical Society (ACS)}, author={Sullivan, Ian and Sahoo, Prangya P. and Fuoco, Lindsay and Hewitt, Andrew S. and Stuart, Sean and Dougherty, Daniel and Maggard, Paul A.}, year={2014}, month={Nov}, pages={6711–6721} }
 @article{xu_hewitt_wang_guan_boltersdorf_maggard_dougherty_gundogdu_2014, title={Intrinsic and extrinsic effects on the electrostatic field at the surface of Bi2Se3}, volume={116}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.4891719}, DOI={10.1063/1.4891719}, abstractNote={The time evolution of electrostatic fields near a Bi2Se3 surface after a mechanical cleave was observed using Second Harmonic Generation. By comparing samples with different bulk doping levels and samples cleaved in different gas environments, these observations indicate multiple contributions to electric field evolution. These include the intrinsic process of Se vacancy diffusion as well as extrinsic processes due to both reactive and nonreactive surface adsorbates.}, number={4}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Xu, Chao and Hewitt, Andy and Wang, Jingying and Guan, Tianshuai and Boltersdorf, Jonathan and Maggard, Paul A. and Dougherty, Daniel B. and Gundogdu, Kenan}, year={2014}, month={Jul}, pages={043519} }
 @article{wang_hewitt_kumar_boltersdorf_guan_hunte_maggard_brom_redwing_dougherty_2014, title={Molecular Doping Control at a Topological Insulator Surface: F-4-TCNQ on Bi2Se3}, volume={118}, ISSN={["1932-7447"]}, DOI={10.1021/jp412690h}, abstractNote={Recent electrical measurements have accessed transport in the topological surface state band of thin exfoliated samples of Bi2Se3 by removing the bulk n-type doping by contact with thin films of the molecular acceptor F4-TCNQ. Here we report on the film growth and interfacial electronic characterization of F4-TCNQ grown on Bi2Se3. Atomic force microscopy shows wetting layer formation followed by 3D island growth. X-ray photoelectron spectroscopy is consistent with this picture and also shows that charge transferred to the molecular layer is localized on nitrogen atoms. Ultraviolet photoelectron spectroscopy shows a work function increase and an upward shift of the valence band edge that suggest significant reduction in carrier density at the Bi2Se3 surface.}, number={27}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Wang, J. and Hewitt, A. S. and Kumar, R. and Boltersdorf, J. and Guan, T. and Hunte, F. and Maggard, P. A. and Brom, J. E. and Redwing, J. M. and Dougherty, D. B.}, year={2014}, month={Jul}, pages={14860–14865} }
 @article{sahoo_maggard_2013, title={Crystal Chemistry, Band Engineering, and Photocatalytic Activity of the LiNb3O8-CuNb3O8 Solid Solution}, volume={52}, ISSN={["1520-510X"]}, DOI={10.1021/ic302649s}, abstractNote={A new solid solution has been prepared in the system LiNb3O8-CuNb3O8, and the impacts of chemical composition and crystal structure have been investigated for the resulting band gap sizes and photocatalytic activities for water reduction to hydrogen under visible light. All members of the solid solution were synthesized by solid-state methods within evacuated fused-silica vessels, and their phase purities were confirmed via powder X-ray diffraction techniques (space group P2(1)/a, a = 15.264(5)-15.367(1) Å, b = 5.031(3)-5.070(1) Å, c = 7.456(1)-7.536(8) Å, and β = 107.35(1)-107.14(8)°, for 0 ≤ x ≤ 1). Rietveld refinements were carried out for the x = 0.09, 0.50, and 0.70 members of the solid solution, which reveal the prevailing isostructurality of the continuous solid solution. The structure consists of chains of (Li/Cu)O6 and NbO6 octahedra. The optical band gap size across the solid solution exhibits a significant red-shift from ∼3.89 eV (direct) to ∼1.45 eV and ∼1.27 eV (direct and indirect) with increasing Cu(I) content, consistent with the change in sample color from white to dark brown to black. Electronic structure calculations based on density-functional theory methods reveal the rapid formation of a new Cu 3d(10)-based valence band that emerges higher in energy than the O 2p band. While the pure LiNb3O8 is a highly active UV-photocatalyst for water reduction, the Li(1-x)Cu(x)Nb3O8 solid is shown to be photocatalytically active under visible-light irradiation for water reduction to hydrogen.}, number={8}, journal={INORGANIC CHEMISTRY}, author={Sahoo, Prangya Parimita and Maggard, Paul A.}, year={2013}, month={Apr}, pages={4443–4450} }
 @article{luo_maggard_2013, title={Effect of Ligand Coordination on the Structures and Visible-Light Photocatalytic Activity of Manganese Vanadate Hybrids}, volume={13}, ISSN={["1528-7505"]}, DOI={10.1021/cg401062f}, abstractNote={A new manganese–vanadate hybrid structure, Mn(H2O)(bpy)V2O6 (I; bpy = 2,2′-bipyridine), has been synthesized via hydrothermal methods and characterized by single crystal X-ray diffraction [P21/n, Z = 4, a = 6.8557(4) A, b = 10.4900(6) A, c = 19.7921(13) A, β = 96.419(4)°], infrared spectroscopy, thermogravimetric analysis, magnetic susceptibility measurements, and UV–vis diffuse reflectance. The structure is comprised of manganese vanadate layers with 2,2’-bipyridine ligands coordinated to the Mn(II) cations. The water molecules coordinated to the manganese sites can be reversibly desorbed at ∼190 °C with the formation of a new hybrid structure before then further decomposing to MnV2O6 upon heating to 300 °C. Notably, I undergoes a reversible structural transformation to Mn(bpy)V4O11(bpy) (II) under hydrothermal conditions. This structural transformation results from additional bpy-ligand coordination to 1/4 of the vanadium sites. Magnetic data indicate Mn(II) cations in both I and II are high spin (S = 5...}, number={12}, journal={CRYSTAL GROWTH & DESIGN}, author={Luo, Lan and Maggard, Paul A.}, year={2013}, month={Dec}, pages={5282–5288} }
 @article{mclamb_sahoo_fuoco_maggard_2013, title={Flux Growth of Single-Crystal Na2Ta4O11 Particles and their Photocatalytic Hydrogen Production}, volume={13}, ISSN={["1528-7483"]}, DOI={10.1021/cg301859d}, abstractNote={Single-crystal particles of the layered natrotantite, i.e., Na2Ta4O11, were prepared within a K2SO4/Na2SO4 flux for flux-to-reactant molar ratios from 12:1 to 1:1 at a reaction temperature of 1000 °C for 2 h. Depending on the conditions, the flux reactions yielded crystals of Na2Ta4O11 that ranged in size from ∼100 nm to ∼1000 nm. The highest and lowest flux amounts yielded more isolated single crystals with sharper facets and surfaces, whereas intermediate flux amounts yielded more aggregates of particles with smooth and rounded surface features. All products were characterized by UV–vis diffuse reflectance techniques and were found to exhibit an indirect bandgap size of ∼4.1–4.3 eV and a larger direct bandgap transition of ∼4.5 eV. When the crystals are suspended in aqueous solutions and irradiated by ultraviolet light, they exhibit stable photocatalytic rates for hydrogen production of ∼13.4 μmol of H2·g–1·h–1 to ∼34.1 μmol of H2·g–1·h–1. The higher photocatalytic rates are found for the single crystal...}, number={6}, journal={CRYSTAL GROWTH & DESIGN}, author={McLamb, Nathan and Sahoo, Prangya Parimita and Fuoco, Lindsay and Maggard, Paul A.}, year={2013}, month={Jun}, pages={2322–2326} }
 @article{arney_fuoco_boltersdorf_maggard_2013, title={Flux Synthesis of Na2Ca2Nb4O13: The Influence of Particle Shapes, Surface Features, and Surface Areas on Photocatalytic Hydrogen Production}, volume={96}, ISSN={["0002-7820"]}, DOI={10.1111/jace.12122}, abstractNote={The layered perovskite (n = 4) Ruddlesden-Popper phase Na2Ca2Nb4O13 was prepared within molten NaCl and Na2SO4 fluxes, yielding either rod-shaped or platelet-shaped particles, respectively. The flux-to-reactant molar ratios of 5:1 or 20:1 were found to significantly influence particle sizes and surface areas, while still maintaining the overall particle shapes. Measured surface areas of flux-prepared Na2Ca2Nb4O13 particles ranged from ∼0.36 to 4.6 m2/g, with the highest surface areas obtained using a 5:1 (NaCl-to-Na2Ca2Nb4O13) molar ratio. All samples exhibited a bandgap size of ∼3.3 eV, as determined by UV–Vis diffuse reflectance measurements. Photocatalytic rates for hydrogen production under ultraviolet light for platinized Na2Ca2Nb4O13 particles in an aqueous methanol solution ranged from ∼230 to 1355 μmol H2 g−1 h−1 when using the photochemical deposition (PCD) method of platinization, and ∼113–1099 μmol H2 g−1 h−1 when using the incipient wetness impregnation (IWI) method of platinization. The higher photocatalytic rates were obtained for the rod-shaped particles with the highest surface areas, with an apparent quantum yield (AQY) measured at ∼6.5% at 350 nm. For the platelet-shaped particles, the higher photocatalytic rates were observed for the sample with the lowest surface area but the largest concentration of stepped edges and grooves observed at the particle surfaces. The latter origin of the photocatalytic activity is confirmed by the significant enhancement of the photocatalytic rates by the PCD method that allows for the preferential deposition of the surface Pt cocatalyst islands at the stepped edges and grooves, while the photocatalytic enhancement is much smaller when using the more general IWI platinization method.}, number={4}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Arney, David and Fuoco, Lindsay and Boltersdorf, Jonathan and Maggard, Paul A.}, year={2013}, month={Apr}, pages={1158–1162} }
 @article{choi_king_maggard_2013, title={Metastable Cu(I)-Niobate Semiconductor with a Low-Temperature, Nanoparticle-Mediated Synthesis}, volume={7}, ISSN={["1936-086X"]}, DOI={10.1021/nn305707f}, abstractNote={A nanoparticle synthetic strategy for the preparation of a new metastable Cu(I)-niobate is described, and that involves multipored Li₃NbO₄ nanoparticles as a precursor. A hydrothermal reaction of HNbO₃ and LiOH·H₂O in PEG200 and water at ∼180 °C yields ∼15-40 nm Li₃NbO₄ particles. These particles are subsequently used in a solvothermal copper(I)-exchange reaction with excess CuCl at 150 °C. Heating these products within the used CuCl flux (mp = 430 °C) to 450 °C for 30 min yields ∼4-12 nm Cu₂Nb₈O₂₁ crystalline nanoparticles, and for a heating time of 24 h yields μm-sized, rod-shaped crystals. The new structure was characterized by single-crystal X-ray diffraction to have a condensed network consisting of NbO₇ polyhedra and chains of elongated CuO₄ tetrahedra. The compound thermally decomposes starting at ∼250 °C and higher temperatures, depending on the particle sizes, owing to the loss of the weakly coordinated Cu(I) cations from the structure and a concurrent disproportionation reaction at its surfaces. Thus, conventional solid-state reactions involving higher temperatures and bulk reagents have proven unsatisfactory for its synthesis. The measured bandgap size is ∼1.43-1.65 eV (indirect) and shows a dependence on the particle sizes. Electronic structure calculations based on density functional theory show that the bandgap transition results from the excitation of electrons at the band edges between filled Cu(I) 3d¹⁰-orbitals and empty Nb(V) 4d⁰-orbitals, respectively. The p-type nature of the Cu₂Nb₈O₂₁ particles was confirmed in photoelectrochemical measurements on polycrystalline films that show a strong photocathodic current under visible-light irradiation in aqueous solutions. These results demonstrate the general utility of reactive nanoscale precursors in the synthetic discovery of new Cu(I)-based semiconducting oxides and which also show promise for use in solar energy conversion applications.}, number={2}, journal={ACS NANO}, author={Choi, Jonglak and King, Nacole and Maggard, Paul A.}, year={2013}, month={Feb}, pages={1699–1708} }
 @article{boltersdorf_maggard_2013, title={Silver Exchange of Layered Metal Oxides and Their Photocatalytic Activities}, volume={3}, ISSN={2155-5435 2155-5435}, url={http://dx.doi.org/10.1021/CS400466B}, DOI={10.1021/CS400466B}, abstractNote={Layered Dion–Jacobson phases RbLaNb2O7 and RbA2Nb3O10 (A = Ca, Sr) and the Ruddlesden–Popper phase Rb2La2Ti3O10 were prepared by solid-state methods at a reaction time of 50 h and a temperature of 1100 °C. The products were silver-exchanged within a AgNO3 flux at a reaction time of 24 h and a temperature of 250 °C. Substitution of silver cations into the interlayer spacing of the layered structures is found to decrease the optical bandgap sizes on average by ∼0.5 to ∼1.0 eV. The products were found by scanning electron microscopy (SEM) to exhibit irregularly shaped platelet morphologies with an average size of ∼1–5 μm across their lateral dimensions and stepped edges ranging from ∼20 to ∼300 nm in height. Significant increases in photocatalytic hydrogen production rates for all silver-exchanged products were observed. The silver-exchanged RbA2Nb3O10 layered structures exhibited the highest photocatalytic hydrogen formation rates under ultraviolet and visible irradiation (∼13,616 μmol H2·g–1·h–1). These ra...}, number={11}, journal={ACS Catalysis}, publisher={American Chemical Society (ACS)}, author={Boltersdorf, Jonathan and Maggard, Paul A.}, year={2013}, month={Oct}, pages={2547–2555} }
 @article{boltersdorf_wong_maggard_2013, title={Synthesis and Optical Properties of Ag(I), Pb(II), and Bi(III) Tantalate-Based Photocatalysts}, volume={3}, ISSN={["2155-5435"]}, DOI={10.1021/cs400707x}, abstractNote={The Ag(I) and Bi(III) tantalates Ag2Ta4O11, BiTa7O19, and Bi7Ta3O18 were prepared by solid-state methods at 1000 °C for 24–48 h. The Pb(II)-containing tantalate PbTa2O6 was prepared at 1100 °C for 24 h, whereas Pb3Ta4O13 and PbTa4O11 were synthesized from a reaction of A2Ta4O11 (A = Na, Ag) precursors with a PbCl2 flux (at 1:1, 5:1, and 10:1 molar ratios) at 700 °C from 24 to 96 h. The PbTa2O6, Pb3Ta4O13, and Bi7Ta3O18 structures consist of TaO6 layers and TaO6 chains/rings with Pb(II) ions located within the cavities. The structures of Ag2Ta4O11, PbTa4O11, and BiTa7O19 consist of layers of TaO7 pentagonal bipyramids that alternate with Ag(I), Pb(II), and Bi(III) cations, respectively. UV–vis diffuse reflectance data were used to measure bandgap sizes for Ag2Ta4O11 (∼3.9 eV), PbTa4O11 (∼3.8–3.95 eV), Pb3Ta4O13 (∼3.0 eV), PbTa2O6 (∼3.6 eV), BiTa7O19 (∼3.6 eV), and Bi7Ta3O18 (∼2.75 eV). A decrease in the band gap was observed with an increase in the Pb(II) or Bi(III) content. Photocatalytic activities of th...}, number={12}, journal={ACS CATALYSIS}, author={Boltersdorf, Jonathan and Wong, Tricia and Maggard, Paul A.}, year={2013}, month={Dec}, pages={2943–2953} }
 @article{joshi_maggard_2012, title={CuNb3O8: A p-Type Semiconducting Metal Oxide Photoelectrode}, volume={3}, ISSN={["1948-7185"]}, DOI={10.1021/jz300477r}, abstractNote={A new p-type CuNb3O8 polycrystalline photoelectrode was investigated and was determined to have indirect and direct bandgap sizes of 1.26 and 1.47 eV, respectively. The p-type polycrystalline film could be prepared on fluorine-doped tin oxide glass and yielded a cathodic photocurrent under visible-light irradiation (λ > 420 nm) with incident photon-to-current efficiencies of up to ∼6-7% and concomitant hydrogen evolution. A Mott-Schottky analysis yielded a flat band potential of +0.35 V versus RHE (pH = 6.3) and a calculated p-type dopant concentration of ∼7.2 × 10(15) cm(-3). The conduction band energies are found to be negative enough for the reduction of water under visible light irradiation. A hole mobility of ∼145 cm(2)/V·s was obtained from J(I)-V(2) measurements using the Mott-Gurney relation, which is ∼50% higher than that typically found for p-type Cu2O. DFT-based electronic structure calculations were used to probe the atomic and structural origins of the band gap transitions and carrier mobility. Thus, a new p-type semiconductor is discovered for potential applications in solar energy conversion.}, number={11}, journal={JOURNAL OF PHYSICAL CHEMISTRY LETTERS}, author={Joshi, Upendra A. and Maggard, Paul A.}, year={2012}, month={Jun}, pages={1577–1581} }
 @article{arney_maggard_2012, title={Effect of Platelet-Shaped Surfaces and Silver-Cation Exchange on the Photocatalytic Hydrogen Production of RbLaNb2O7}, volume={2}, ISSN={["2155-5435"]}, DOI={10.1021/cs200643h}, abstractNote={The layered Dion-Jacobsen RbLaNb2O7 photocatalyst was prepared in platelet-shaped morphologies using a RbCl flux and with a modulation of the particle morphologies using from 1:1–10:1 (RbCl:RbLaNb2O7) molar ratios and reaction times of 24 h–1 h at a temperature of 1100 °C. Further, the silver-ion exchanged AgLaNb2O7 product could be prepared by reaction of the RbLaNb2O7 particles within a AgNO3 flux at 250 °C for 24 h. These products were characterized by powder X-ray diffraction (e.g., Imma, a = 5.4763(8) A, b = 22.4042(2) A, c = 5.1576(3) A, for RbLaNb2O7; I41/acd, a = 7.7803(2) A, c = 42.5692(4) A, for AgLaNb2O7). At a 10:1 flux ratio, rounded-platelet morphologies with smooth surfaces were observed by scanning electron microscopy (SEM) with thicknesses of ∼100–300 nm and lateral dimensions of ∼1.0–6.0 μm. These particle dimensions and morphologies were conserved during the silver-exchange reactions. Photocatalytic rates for hydrogen production were measured in aqueous methanol and yielded maximal rate...}, number={8}, journal={ACS CATALYSIS}, author={Arney, David and Maggard, Paul A.}, year={2012}, month={Aug}, pages={1711–1717} }
 @article{palasyuk_maggard_2012, title={NaCu(Ta1−yNby)4O11 solid solution: A tunable band gap spanning the visible-light wavelengths}, volume={191}, ISSN={0022-4596}, url={http://dx.doi.org/10.1016/j.jssc.2012.03.023}, DOI={10.1016/j.jssc.2012.03.023}, abstractNote={The new solid-solution NaCu(Ta1−yNby)4O11 (0≤y≤0.7) was synthesized by solid-state methods in the form of bulk powders that ranged from light-yellow to brown colored and were characterized by powder X-ray diffraction techniques (Space group R-3c (#167); Z=6; a=6.214(1)–6.218(1) Å and c=36.86(1)–36.94(1) Å). Full-profile Rietveld refinements confirmed a site-differentiated ordering of the Cu(I) and Na cations, i.e., occupying the 12c (linear environment) and 18d (seven-coordinate environment) crystallographic sites respectively. Conversely, a statistical mixture of Ta(V) and Nb(V) cations occurred over the 6b (octahedral environment) or the 18e (pentagonal-bipyramidal environment) crystallographic sites, without any preferential segregation. The UV-Vis diffuse reflectance spectra showed a significant red-shift of the optical bandgap size (indirect) from ∼2.70 eV to ∼1.80 eV across the solid solution with increasing Nb(V) content. Electronic-structure calculations using the tight-binding linear-muffin-tin-orbital approach showed that the reduction in bandgap size arises from the introduction of the lower-energy Nb 4d0 orbitals into the conduction band and consequently a lower energy of the conduction band edge. The lowest-energy bandgap transitions were found to be derived from electronic transitions between the filled Cu(I) and the empty Nb(V) d-orbitals, with a small amount of mixing with the O 2p orbitals. The resulting conduction and valence band energies are found to approximately bracket the redox potentials for water reduction and oxidation, and meeting the thermodynamic requirements for photocatalytic water-splitting reactions.}, journal={Journal of Solid State Chemistry}, publisher={Elsevier BV}, author={Palasyuk, Olena and Maggard, Paul A.}, year={2012}, month={Jul}, pages={263–270} }
 @article{fuoco_joshi_maggard_2012, title={Preparation and Photoelectrochemical Properties of p-type Cu5Ta11O30 and Cu3Ta7O19 Semiconducting Polycrystalline Films}, volume={116}, ISSN={["1932-7447"]}, DOI={10.1021/jp300267v}, abstractNote={New p-type polycrystalline films of semiconducting Cu5Ta11O30 and Cu3Ta7O19 were prepared on fluorine-doped tin oxide (FTO) glass starting from their CuCl-flux synthesis as highly faceted micrometer-sized particles. The particles were annealed on FTO at 400–500 °C, followed by a mild oxidation in air at between 250 and 550 °C. In an aqueous 0.5 M Na2SO4 electrolyte solution (pH = 6.3), the films exhibit strong cathodic photocurrents under irradiation by visible and/or ultraviolet light, which increased with higher annealing and oxidation temperatures owing to increased p-type carrier concentration and better electrical contact between particles. Thermogravimetric analyses show that the oxidation treatments result in an oxygen uptake at concentrations of ∼3 × 1020 cm–3 at 250 °C, to ∼4 × 1021 cm–3 at 550 °C, with the higher temperatures leading to the decomposition of the film. The Cu5Ta11O30 and Cu3Ta7O19 bulk powders exhibit band-gap sizes of ∼2.59 and ∼2.47 eV, respectively, and show an onset of their c...}, number={19}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Fuoco, Lindsay and Joshi, Upendra A. and Maggard, Paul A.}, year={2012}, month={May}, pages={10490–10497} }
 @article{arney_watkins_maggard_2011, title={Effects of Particle Surface Areas and Microstructures on Photocatalytic H-2 and O-2 Production over PbTiO3}, volume={94}, ISSN={["1551-2916"]}, DOI={10.1111/j.1551-2916.2010.04262.x}, abstractNote={The visible-light photocatalyst PbTiO3 was prepared in molten NaCl and PbO fluxes using 0.5:1–20:1 flux-to-reactant molar ratios by heating to 1000°C for a duration of 1 h. Yellow-colored powders were obtained in high purity, as confirmed by powder X-ray diffraction and exhibited a bandgap size of ∼2.75 eV as determined by UV–Vis diffuse reflectance measurements. Roughly spherical and cubic shaped particles with homogeneous microstructures were observed with sizes ranging from ∼100 to 6 000 nm, and surface areas ranging from 0.56 to 2.63 m2/g. The smallest particle-size distributions and highest surface areas were obtained for the 10:1 NaCl flux molar ratio. By comparison, solid-state preparations of PbTiO3 particles exhibit no well-controlled sizes or microstructures. The water-splitting photocatalytic activities of the PbTiO3 particles were evaluated in visible light (λ>420 nm), and yielded maximum rates of 27.4 μmol·H2·(g·h)−1 for the PbTiO3 prepared using a 1:1 PbO molar ratio and 183 μmol·O2·(g·h)−1 for the solid-state prepared sample. The rates were inversely correlated with the particle surface areas. The relationship between particle morphology and photocatalytic activity provides important insights into understanding the origins of photocatalysis in metal-oxides.}, number={5}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Arney, David and Watkins, Tylan and Maggard, Paul A.}, year={2011}, month={May}, pages={1483–1489} }
 @article{zou_lin_maggard_deiters_2011, title={Efficacy of C-N Coupling Reactions with a New Multinuclear Copper Complex Catalyst and Its Dissociation into Mononuclear Species}, volume={2011}, ISSN={["1099-0690"]}, DOI={10.1002/ejoc.201100399}, abstractNote={A new tetranuclear copper(I)–pyridazine (pda)/rhenate hybrid has been synthesized under hydrothermal conditions and structurally characterized by X-ray crystallography. The activity of this catalyst, as well as its dissociation into mononuclear species, was investigated in homogeneous C–N arylation reactions. A variety of N-arylamides and -azoles were synthesized in good to excellent yields, revealing the effect of polynuclear versus mononuclear Cu complexation in this type of coupling reaction.}, number={22}, journal={EUROPEAN JOURNAL OF ORGANIC CHEMISTRY}, author={Zou, Yan and Lin, Haisheng and Maggard, Paul A. and Deiters, Alexander}, year={2011}, month={Aug}, pages={4154–4159} }
 @article{lin_maggard_2011, title={Investigation of Trimetallic Ligand-Pillared Oxyfluorides: Ag2Cu(pzc)2MO x F6−x (M = Mo, Nb, and W)}, volume={41}, ISSN={["1572-8854"]}, DOI={10.1007/s10870-011-0139-y}, number={10}, journal={Journal of Chemical Crystallography}, author={Lin, H and Maggard, P.A.}, year={2011}, pages={1552–1559} }
 @article{fuoco_rodriguez_peppel_maggard_2011, title={Molten-Salt-Mediated Syntheses of Sr2FeReO6, Ba2FeReO6, and Sr2CrReO6: Particle Sizes, B/B ' Site Disorder, and Magnetic Properties}, volume={23}, ISSN={["1520-5002"]}, DOI={10.1021/cm202545z}, abstractNote={The half-metallic double-perovskites Sr2FeReO6, Ba2FeReO6, and Sr2CrReO6 were synthesized in high purity and homogeneity using a NaCl/KCl molten flux at 750–800 °C in as little as 3–6 h. The partic...}, number={24}, journal={CHEMISTRY OF MATERIALS}, author={Fuoco, Lindsay and Rodriguez, Dianny and Peppel, Tim and Maggard, Paul A.}, year={2011}, month={Dec}, pages={5409–5414} }
 @article{joshi_palasyuk_maggard_2011, title={Photoelectrochemical Investigation and Electronic Structure of a p-Type CuNbO3 Photocathode}, volume={115}, ISSN={["1932-7447"]}, DOI={10.1021/jp204631a}, abstractNote={A new p-type CuNbO3 photoelectrode was prepared on fluorine-doped tin oxide (FTO) glass and characterized by X-ray diffraction (XRD), UV–vis spectroscopy, and photoelectrochemical techniques. Solid-state syntheses yielded a red-colored CuNbO3 phase (space group: C2/m (No. 12), Z = 8, a = 9.525(1) A, b = 8.459(2) A, c = 6.793(1) A, β = 90.9(2)°) with a measured optical bandgap size of ∼2.0 eV. Phase-pure samples could be deposited and annealed on FTO slides at 400 °C under vacuum. Photoelectrochemical measurements showed the onset of a photocathodic current driven under visible-light irradiation and reaching incident-photon-to-current efficiencies exceeding ∼5%. The p-type CuNbO3 film also exhibits a stable photocurrent and notable resistance to photocorrosion, as shown by X-ray diffraction. Electronic structure calculations based on density functional theory reveal the visible-light absorption originates from a nearly direct bandgap transition owing primarily to copper-to-niobium (d10-to-d0) excitations. ...}, number={27}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Joshi, Upendra A. and Palasyuk, Andriy M. and Maggard, Paul A.}, year={2011}, month={Jul}, pages={13534–13539} }
 @article{gupta_maggard_corbett_2010, title={A Bismuth-Stabilized Metal-Rich Telluride Lu9Bi≈1.0Te≈1.0 - Synthesis and Characterization}, volume={2010}, ISSN={1434-1948}, url={http://dx.doi.org/10.1002/ejic.201000147}, DOI={10.1002/ejic.201000147}, abstractNote={Synthetic reactions aimed at bismuth incorporation into rare-earth-metal-rich tellurides yielded Lu 9 Bi ≈1.00 Te ≈1.00 over a small range of compositions, but no analogues with Gd, Tb, Er, or Y. A single-crystal X-ray diffraction analysis gave the composition Lu 9 Bi 0.99(3) Te 1.01 in the acentric orthorhombic space group Cmc2 1 at ambient temperature. This is isostructural with the re-refined Sc 9 Te 2 earlier reported in a monoclinic Cc structure. Lu 9 Bi ≈1.00 Te ≈1.00 represents the first ternary compound in this structure type and the third lutetium-richest compound after Lu 8 Te and Lu 7 Te. The structure contains 3 × 3 columns of Lu in the form of condensed distorted trans-edge-sharing octahedral chains along α. The Te and Bi anions lie within tricapped trigonal prisms of Lu. Generally shorter Lu-Lu interactions lie in the interior of 3 × 3 metal columns compared with those on the periphery for which fewer Lu-Lu interactions and polar covalent bonding with neighboring tellurium weaken Lu-Lu bonding. Limiting Lu-Lu distances around 3.18 A are by far the shortest among reduced lutetium tellurides. LMTO-type ab initio electronic structure calculations reveal a metallic nature and show that strong polar bonding of Lu to both the more electronegative Bi and Te leaves Lu relatively oxidized, many 5d states falling above the Fermi level. Stronger Lu-Lu bonding within the metal columns is also indicated by their larger individual Hamilton populations. The isostructural Lu 9 SbTe and Sc 9 BiTe were also shown to exist according to powder data.}, number={18}, journal={European Journal of Inorganic Chemistry}, publisher={Wiley}, author={Gupta, Shalabh and Maggard, Paul A. and Corbett, John D.}, year={2010}, month={Apr}, pages={2620–2625} }
 @article{gupta_maggard_corbett_2010, title={A bismuth-stabilized metal-rich telluride Lu9Bi approximate to 1.0Te approximate to 1.0 - synthesis and characterization}, number={18}, journal={European Journal of Inorganic Chemistry}, author={Gupta, S. and Maggard, P. A. and Corbett, J. D.}, year={2010}, pages={2620–2625} }
 @article{arney_hardy_greve_maggard_2010, title={Flux synthesis of AgNbO3: Effect of particle surfaces and sizes on photocatalytic activity}, volume={214}, ISSN={["1010-6030"]}, DOI={10.1016/j.jphotochem.2010.06.006}, abstractNote={The molten-salt flux synthesis of AgNbO3 particles was performed in a Na2SO4 flux using 1:1, 2:1 and 3:1 flux-to-reactant molar ratios and heating to 900 °C for reaction times of 1–10 h. Rectangular-shaped particles are obtained in high purity and with homogeneous microstructures that range in size from ∼100 to 5000 nm and with total surface areas from 0.16 to 0.65 m2 g−1. The smallest particle-size distributions and highest surface areas were obtained for the largest amounts of flux (3:1 ratio) and the shortest reaction time (1 h). Measured optical bandgap sizes of the AgNbO3 products were in the range of ∼2.8 eV. The photocatalytic activities of the AgNbO3 particles for H2 formation were measured in visible light (λ > 420 nm) in an aqueous methanol solution and varied from ∼1.7 to 5.9 μmol H2 g−1 h−1. The surface microstructures of the particles were evaluated using field-emission SEM, and the highest photocatalytic rates of the AgNbO3 particles were correlated with the formation of high densities of ∼20–50 nm terraced surfaces. By comparison, the solid-state sample showed no well-defined morphology or microstructure. Thus, the results presented herein demonstrate the utility of flux-synthetic methods in targeting new particles sizes and surface microstructures for the enhancement and understanding of photocatalytic reactivity over metal-oxide particles.}, number={1}, journal={JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY}, author={Arney, David and Hardy, Christopher and Greve, Benjamin and Maggard, Paul A.}, year={2010}, month={Jul}, pages={54–60} }
 @article{lin_maggard_2010, title={Microporosity, Optical Bandgap Sizes, and Photocatalytic Activity of M(I)-Nb(V) (M = Cu, Ag) Oxyfluoride Hybrids}, volume={10}, ISSN={1528-7483 1528-7505}, url={http://dx.doi.org/10.1021/cg9013625}, DOI={10.1021/cg9013625}, abstractNote={Using hydrothermal methods, a new series of five M(I)−Nb(V) oxyfluoride hybrid solids was prepared having the compositions [Cu(pyz)]2NbOF5 (1, pyz = pyrazine), Ag(pyz)NbOF4 (2), M(bpy)NbOF4·2H2O (3, M = Cu; 4, M = Ag; bpy = 4,4′-bipyridine), and [Cu(dpe)]2NbOF5·8H2O (5, dpe = 1,2-bis(4-pyridyl)-ethene). Each of the hybrid solids consists of layered structures with bridging ligands that coordinate via the Ag+ or Cu+ (i.e., M+) sites in each layer. The structure of 1 is comprised of [Cu2(pyz)22+]n double chains that are cross-linked into double layers by coordination to partially O/F-disordered [NbOF5]2− octahedra. Hybrids 2−4 contain pyz- and bpy-pillared [MNbOF4] layers, with the longer bpy ligand affording two interlayer water molecules per M+ site. These [MNbOF4] layers consist of ordered polar [NbOF4]− chains that are bridged via the M+ sites and that orient in alternating directions. The longest ligand in 5, dpe, results in a 3-fold interpenetrating pillared network consisting of [Cu(dpe)+]n chains br...}, number={3}, journal={Crystal Growth & Design}, publisher={American Chemical Society (ACS)}, author={Lin, Haisheng and Maggard, Paul A.}, year={2010}, month={Mar}, pages={1323–1331} }
 @article{joshi_palasyuk_arney_maggard_2010, title={Semiconducting Oxides to Facilitate the Conversion of Solar Energy to Chemical Fuels}, volume={1}, ISSN={["1948-7185"]}, DOI={10.1021/jz100961d}, abstractNote={The rising significance of producing useful chemical fuels from sunlight has motivated an upsurge of photochemical research, as shown by the growing diversity of chromophores, redox catalysts, and reactivity studies. However, their synergistic integration within artificial photosynthetic systems requires shareable platforms. Early transition-metal oxides have exhibited effective chromophoric/electronic properties across many systems, which has enabled outstanding photocatalytic water splitting efficiencies, but only under ultraviolet irradiation. Semiconducting modifications of these oxides have been investigated that both extend their absorption deep into the visible region and also closely bracket the redox potentials for water splitting and carbon dioxide reduction. Their coupling to surface-anchored molecular catalysts in order to lower kinetic barriers and provide product selectivity is anticipated to lead to studies involving the dynamic interplay of photons, charge carriers, and catalyst turnover.}, number={18}, journal={JOURNAL OF PHYSICAL CHEMISTRY LETTERS}, author={Joshi, Upendra A. and Palasyuk, Andriy and Arney, David and Maggard, Paul A.}, year={2010}, month={Sep}, pages={2719–2726} }
 @article{enterkin_maggard_ishiwata_marks_poeppelmeier_azuma_takano_2010, title={Single crystal growth and structure of La4Cu3MoO12}, volume={183}, ISSN={0022-4596}, url={http://dx.doi.org/10.1016/j.jssc.2009.11.019}, DOI={10.1016/j.jssc.2009.11.019}, abstractNote={We report the synthesis and structure determination of single crystals of La4Cu3MoO12 grown from a CuO/KCl flux. This material, whose structure had previously been reported based solely on polycrystalline diffraction data, shows frustrated magnetic behavior and an anti-ferromagnetic ordering of spin-1/2 triangles at low temperatures. The structural and atomic parameters determined from the single crystal data are in very good agreement with those reported previously. However, HREM data showed evidence for disorder in the stacking of the Cu3MoO4 planes, and thus a twinned structural refinement in space group P21/m was replaced by an equivalent disordered structural model in space group Pm. This development of a synthetic route to single crystals of La4Cu3MoO12 will allow a more detailed investigation of its complex electronic and magnetic properties.}, number={3}, journal={Journal of Solid State Chemistry}, publisher={Elsevier BV}, author={Enterkin, James A. and Maggard, Paul A. and Ishiwata, Shintaro and Marks, Laurence D. and Poeppelmeier, Kenneth R. and Azuma, Masaki and Takano, Mikio}, year={2010}, month={Mar}, pages={551–556} }
 @article{palasyuk_palasyuk_maggard_2010, title={Site-Differentiated Solid Solution in (Na1-xCux)(2)Ta4O11 and Its Electronic Structure and Optical Properties}, volume={49}, ISSN={["1520-510X"]}, DOI={10.1021/ic101529n}, abstractNote={The (Na(1-x)Cu(x))(2)Ta(4)O(11) (0 ≤ x ≤ 0.78) solid-solution was synthesized within evacuated fused-silica vessels and characterized by powder X-ray diffraction techniques (space group: R3c (#167), Z = 6, a = 6.2061(2)-6.2131(2) Å, c = 36.712(1)-36.861(1) Å, for x = 0.37, 0.57, and 0.78). The structure consists of single layers of TaO(7) pentagonal bipyramids as well as layers of isolated TaO(6) octahedra surrounded by Na(+) and Cu(+) cations. Full-profile Rietveld refinements revealed a site-differentiated substitution of Na(+) cations located in the 12c (Wyckoff) crystallographic site for Cu(+) cations in the 18d crystallographic site. This site differentiation is driven by the linear coordination geometry afforded at the Cu(+) site compared to the distorted seven-coordinate geometry of the Na(+) site. Compositions more Cu-rich than x ~ 0.78, that is, closer to "Cu(2)Ta(4)O(11)", could not be synthesized owing to the destabilizing Na(+)/Cu(+) vacancies that increase with x up to the highest attainable value of ~26%. The UV-vis diffuse reflectance spectra show a significant red-shift of the bandgap size from ~4.0 eV to ~2.65 eV with increasing Cu(+) content across the series. Electronic structure calculations using the TB-LMTO-ASA approach show that the reduction in bandgap size arises from the introduction of Cu 3d(10) orbitals and the formation of a new higher-energy valence band. A direct bandgap transition emerges at k = Γ that is derived from the filled Cu 3d(10) and the empty Ta 5d(0) orbitals, including a small amount of mixing with the O 2p orbitals. The resulting conduction and valence band energies are determined to favorably bracket the redox potentials for water reduction and oxidation, meeting the thermodynamic requirement for photocatalytic water-splitting reactions.}, number={22}, journal={INORGANIC CHEMISTRY}, author={Palasyuk, Olena and Palasyuk, Andriy and Maggard, Paul A.}, year={2010}, month={Nov}, pages={10571–10578} }
 @article{palasyuk_maggard_2010, title={Structural modification and optical reflectivity of new gold-indide intermetallic compounds}, volume={491}, ISSN={["1873-4669"]}, DOI={10.1016/j.jallcom.2009.10.152}, abstractNote={The gold–indide SrAu3.36(2)In4.64 contains a novel 3D Au/In network, which can be described in terms of complex ∞3[Au,In]82− polyanions with strontium atoms filling hexagonal cages that are part of highly condensed infinite channels. This new intermetallic compound represents a small decrease in the indium content, i.e., as compared to SrAu3.76(4)In4.24, and results in a significant orthorhombic to monoclinic structural transformation. Electronic structure calculations by Linear Muffin-Tin-Orbital (LMTO) methods show that Au–In interactions are predominant in its structural stabilization. UV–vis measurements show a generally lower reflectivity and higher absorption, as compared to elemental Au.}, number={1-2}, journal={JOURNAL OF ALLOYS AND COMPOUNDS}, author={Palasyuk, A. and Maggard, Paul A.}, year={2010}, month={Feb}, pages={81–84} }
 @article{palasyuk_palasyuk_maggard_2010, title={Syntheses, optical properties and electronic structures of copper(I) tantalates: Cu5Ta11O30 and Cu3Ta7O19}, volume={183}, ISSN={["1095-726X"]}, DOI={10.1016/j.jssc.2010.01.030}, abstractNote={Two copper tantalates, Cu5Ta11O30 (1) and Cu3Ta7O19 (2), were synthesized by solid-state and flux synthetic methods, respectively. A synthetic route yielding 2 in high purity was found using a CuCl flux at 800oC and its structure was characterized using powder X-ray diffraction (XRD) data (P63/m (no. 176), Z=2, a=6.2278(1) Å, and c=20.1467(3) Å). The solid-state synthesis of 1 was performed using excess Cu2O that helped to facilitate the growth of single crystals and their characterization by XRD (P6¯2c (no. 190), Z=2, a=6.2252(1) Å, and c=32.516(1) Å). The atomic structures of both copper tantalates consist of alternating single and double layers of TaO7 pentagonal bipyramids that are bridged by a single layer of isolated TaO6 octahedra and linearly-coordinated Cu+. Measured optical bandgap sizes of ∼2.59 and ∼2.47 eV for 1 and 2 were located well within visible-light energies and were consistent with their orange–yellow colours. Each also exhibits optical absorption coefficients at the band edge of ∼700 and ∼275 cm−1, respectively, and which were significantly smaller than that for NaTaO3 of ∼1450 cm−1. Results of LMTO calculations indicate that their visible-light absorption is attributable mainly to indirect bandgap transitions between Cu 3d10 and Ta 5d0 orbitals within the TaO7 pentagonal bipyramids.}, number={4}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Palasyuk, Olena and Palasyuk, Andriy and Maggard, Paul A.}, year={2010}, month={Apr}, pages={814–822} }
 @article{lin_wu_maggard_2009, title={Ligand-Based Modification of the Structures and Optical Properties of New Silver(I)-Rhenate(VII) Oxide/Organic Hybrid Solids}, volume={48}, ISSN={["1520-510X"]}, DOI={10.1021/ic901749r}, abstractNote={A new series of silver(I)-rhenate(VII) hybrids was systematically prepared under hydrothermal conditions from eight different N-donor organic ligands (isonicotinate = inca, pyrazine-2-carboxylate = pzc, 1,2,4-triazole = tro, pyridazine = pda, 4,4'-bipyridine = bpy, 1,2-bis(4-pyridyl)-ethane = dpa, 2,3-bis(2-pyridyl)pyrazine = bpp, and tetra-2-pyridinylpyrazine = tpp), and their resulting structures and optical properties were investigated. The reactions targeted a 1:1 molar ratio of Ag/Re, and new hybrid solids were prepared with the compositions Ag(bpp)ReO(4) (1), Ag(tpp)ReO(4) x H(2)O (2), Ag(Hinca)(2)ReO(4) x H(2)O (3), Ag(tro)ReO(4) (4), Ag(pda)ReO(4) x 1/2 H(2)O (5), Ag(Hpzc)ReO(4) (6), Ag(2)(Hpzc)(pzc)(H(2)O)ReO(4) (7), Ag(bpy)ReO(4) (8), and Ag(dpa)(2)ReO(4) (9). Hybrid solids 1, 2, and 3 each exhibit low-dimensional structures, consisting of [Ag(2)(bpp)(4)](2+) and [Ag(2)(Hinca)(4)](2+) dimers in 1 and 3, respectively, and [Ag(tpp)](n)(n+) chains in 2. Hybrid solids 4 and 5 contain a [Ag(tro)](+) chain and a [Ag(3)(pda)(3)](3+) cyclic trimer, respectively, that are both ReO(4)-bridged into layered structures. Both 6 and 8 consist of ligand-pillared "AgReO(4)" layers, while 7 is a Re-deficient analogue of 6 that contains ligand-pillared [Ag(2)(H(2)O)ReO(4)](+) layers where H(2)O replaces the missing ReO(4)(-) anion. The hybrid networks of 8 and 9 are interpenetrating, owing to the length of the bpy and dpa ligands, and consist of bpy-pillared "AgReO(4)" layers and ReO(4)-filled [Ag(dpa)(2)](+) diamond-type networks that are 2-fold and 6-fold interpenetrating, respectively. Their optical properties and thermal stabilities were investigated using UV-vis transmittance, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The measured properties were analyzed with respect to the varying structural modifications. The Ag-ReO(4) network dimensionalities, Ag coordination environments, and the ligand lengths and geometries are found to play important roles in the absorption coefficients, bandgap sizes, and whether the structure collapses softly to give condensed AgReO(4), respectively.}, number={23}, journal={INORGANIC CHEMISTRY}, author={Lin, Haisheng and Wu, Xiaomeng and Maggard, Paul A.}, year={2009}, month={Dec}, pages={11265–11276} }
 @article{lin_maggard_2009, title={Ligand-Mediated Interconversion of Multiply-Interpenetrating Frameworks in Cu-I/Re-VII-Oxide Hybrids}, volume={48}, ISSN={["1520-510X"]}, DOI={10.1021/ic900735n}, abstractNote={Two new copper(I)-rhenate(VII) hybrid solids, Cu(bpy)ReO(4) (I) and Cu(bpy)(2)ReO(4).0.5H(2)O (II) (bpy = 4,4'-bipyridine), with 2-fold and 4-fold interpenetrating networks, respectively, were prepared from hydrothermal reactions, and their structures characterized by single-crystal X-ray diffraction [I, Pbca (No. 61), Z = 8, a = 10.8513(3) A, b = 12.9419(4) A, c = 15.6976(5) A; II, P1 (No. 2), Z = 2, a = 11.8190(4) A, b = 12.6741(4) A, c = 13.7585(5) A, alpha = 85.8653(13) degrees, beta = 81.6197(13) degrees, gamma = 84.0945(11) degrees]. The structure of I contains 6(3) nets of neutral CuReO(4) layers that are pillared via bpy ligands on the Cu sites {CuO(3)N(2)} to yield a 2-fold interpenetrating pillared-layered network. Conversely, the structure of II consists of a 4-fold interpenetrating diamond-type network with tetrahedral {CuN(4)} coordination nodes that are bridged by bpy ligands, with both H(2)O and ReO(4)(-) within the pores. A surprising reversible structural interconversion between these two interpenetrating structures is possible via the insertion and removal of a single bpy ligand and (1/2)H(2)O per copper atom. The structural interconversion is accompanied by a change in color from yellow to red for I and II, respectively. Measured UV-vis diffuse reflectance spectra exhibit a significant red-shift in the absorption edge of approximately 0.3 eV, with the optical bandgap size decreasing from approximately 2.5 eV to approximately 2.2 eV for I and II, respectively. X-ray photoelectron spectra and electronic structure calculations indicate that the valence band derived from the Cu 3d and N 2p orbitals in II are pushed higher in energy compared to those in I because of the coordination of the additional bpy ligand. There is a much smaller change in the energy of the conduction band that is derived from the Re 5d orbitals. These results demonstrate that the ligand-mediated structural transformations of (d(0)/d(10))-hybrid solids represent a new and convenient low-temperature approach to modulate their optical bandgap sizes toward the visible wavelengths for use with solar energy.}, number={18}, journal={INORGANIC CHEMISTRY}, author={Lin, Haisheng and Maggard, Paul A.}, year={2009}, month={Sep}, pages={8940–8946} }
 @article{arney_porter_greve_maggard_2008, title={New molten-salt synthesis and photocatalytic properties of La2Ti2O7 particles}, volume={199}, ISSN={["1010-6030"]}, DOI={10.1016/j.jphotochem.2008.06.005}, abstractNote={The (1 1 0)-layered perovskite La2Ti2O7 photocatalyst has been synthesized in high purities and in homogeneous microstructures within a molten Na2SO4/K2SO4 flux in short reaction times of ∼1–10 h. The La2Ti2O7 particle morphologies and sizes were investigated as a function of flux amounts (flux:La2Ti2O7 molar ratios of 1:1, 2:1, 5:1, and 10:1) and reaction times (1, 2, 5, and 10 h). Powder X-ray diffraction confirmed the structure type and high purity, and UV–vis diffuse reflectance measurements yielded optical bandgap sizes of ∼3.75–3.81 eV. Rectangular platelet morphologies are obtained with maximal dimensions of ∼500–5000 nm, but with thicknesses down to <100 nm, and which decrease in size with increasing amounts of flux used in the synthesis. Photocatalytic activities of the La2Ti2O7 products were measured under ultraviolet irradiation in aqueous methanol solutions and yielded rates for hydrogen production from 55 to 140 μmol H2 h−1 g−1, with the maximum photocatalytic rates for the smallest particles, e.g. for 1:1 and 10:1 flux:La2Ti2O7 ratios respectively. The flux-prepared La2Ti2O7 products were also photocatalytically active in pure deionized water, yielding maximal rates for hydrogen formation of 31 μmol H2 h−1 g−1. The observed photocatalytic rates were up to nearly two times greater than that obtained when La2Ti2O7 was prepared by the reported solid-state method, and indicate that the exposed crystallite edges and the (0 1 0) and (0 0 1) crystal faces play a key role in the photocatalysis mechanisms for hydrogen formation.}, number={2-3}, journal={JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY}, author={Arney, David and Porter, Brittany and Greve, Benjamin and Maggard, Paul A.}, year={2008}, month={Sep}, pages={230–235} }
 @article{lin_maggard_2008, title={Synthesis and structures of a new series of silver-vanadate hybrid solids and their optical and photocatalytic properties}, volume={47}, ISSN={["1520-510X"]}, DOI={10.1021/ic8004129}, abstractNote={Three new silver-vanadate hybrid solids, [Ag(bpy)]4V4O12 x 2 H2O (I), [Ag(dpa)]4V4O12 x 4 H2O (II), and Ag4(pzc)2V2O6 (III) (bpy = 4,4'-bipyridine, dpa = 1,2-bis(4-pyridyl)-ethane, pzc = pyrazinecarboxylate), were synthesized by hydrothermal methods and characterized using single crystal X-ray diffraction (I, P2(1)/c, Z = 4, a = 11.375(2) A, b = 14.281(4) A, c = 13.598(3) A, beta = 91.46(1) degrees; II, P2(1)/c, Z = 8, a = 13.5748(3) A, b = 15.3372(4) A, c = 14.1854(3) A, beta = 114.1410(9) degrees; III, P1, Z = 2, a = 3.580(1) A, b = 11.839(4) A, c = 19.321(7) A, alpha = 89.110(7) degrees, beta = 87.719(9) degrees, gamma = 86.243(8) degrees), thermogravimetric analysis, and UV-vis diffuse reflectance. The structures of I and II are constructed from neutral {Ag4V4O12}n layers of clusters that are pillared via the coordination of organic ligands (bpy for I and dpa for II) to the Ag sites in each layer. Conversely, the structure of III is composed of a three-dimensional {Ag2(pzc)(+)}n coordination network with channels containing {VO3(-)}n chains. The lattice water molecules can be removed upon heating to > or = 180 degrees C for I (reversibly) and to > or = 120 degrees C for II (irreversibly). All three decompose with the removal of organic ligands at higher temperatures of > 200-300 degrees C. Their optical bandgap sizes were measured to be 2.77 eV for I, 2.95 eV for II, and 2.45 eV for III, which decrease most notably as a result of the band widening for the more extended vanadate structure in III. All three hybrid solids are photocatalytically active for the decomposition of methylene blue under UV light (lambda < 400 nm; 1.01, 0.64, and 2.65 mg L(-1) h(-1) for I, II, and III, respectively), while only III exhibits a high activity under visible-light irradiation (lambda > 400 nm; 1.20 mg L(-1) h(-1) ). These new hybrid solids are among the first reported to exhibit high photocatalytic activities under either ultraviolet or visible-light irradiation and have also been analyzed with respect to the effect of the different organic ligands on their atomic- and electronic-structures.}, number={18}, journal={INORGANIC CHEMISTRY}, author={Lin, Haisheng and Maggard, Paul A.}, year={2008}, month={Sep}, pages={8044–8052} }
 @article{maggard_porob_2007, title={A Rapid Flux-Assisted Synthetic Approach Towards The Bandgap Engineering of Layered Perovskites}, volume={19}, ISSN={["0897-4756"]}, DOI={10.1021/cm062743a}, abstractNote={The metal-halide-exchanged (CuCl)LaM2O7 and (CuCl)Ca2M3O10 (M = Nb, Ta) are obtained in high purity from the parent layered perovskite hosts using a rapid synthetic approach in molten alkali-nitrate or alkali-bisulfate fluxes at 300−400 °C in only 1 −2 h. The insertion of CuCl layers also introduces new higher-energy valence bands into the electronic structure of the perovskite hosts and lowers their band gap sizes by 1.0−1.4 eV into the visible region, shown in TOC Figure. Thus, the CuCl layers are shown to modify both the atomic and electronic structures and suggest their potential use in visible-light sensitization of photocatalysts.}, number={5}, journal={Chemical Materials}, author={Maggard, P and Porob, D.G.}, year={2007}, month={Jan}, pages={970–972} }
 @article{lin_maggard_2007, title={Copper(I)-rhenate hybrids: Syntheses, structures, and optical properties}, volume={46}, ISSN={["0020-1669"]}, DOI={10.1021/ic061767g}, abstractNote={The new copper(I) rhenates, CuReO4(pyz) (I) and Cu3ReO4(q6c)2 (II) (pyz = pyrazine; q6c = quinoline-6-carboxylate), were synthesized by hydrothermal methods at 140-150 degrees C, and their structures determined via single-crystal X-ray diffraction (I, P21/n, No. 14, Z = 4, a = 7.972(1) A, b = 11.928(2) A, c = 8.430(1) A, beta = 102.161(2) degrees ; II, P21, No. 4, Z = 2, a = 8.253(2) A, b = 6.841(2) A, c = 18.256(6) A, beta = 101.37(2) degrees ) and characterized by thermogravimetric analyses and UV-vis diffuse reflectance. The structure of I contains 'CuReO4' layers that are pillared through bridging pyrazine ligands via the Cu sites, while the structure of II is polar and contains chains of 'Cu2ReO4' that are condensed into layers by coordination to linear 'Cu(q6c)2' bridges between the chains. In contrast to air-sensitive CuReO4, both hybrid analogues are stable in air owing to a stabilization of the Cu1+ oxidation state by N-donating ligands, but decompose upon heating with the removal of the organic ligands, which for I yields crystalline CuReO4. UV-vis diffuse reflectance measurements and electronic structure calculations on all three copper perrhenates, I, II, and CuReO4, show that each exhibits an optical band gap of approximately 2.1-2.2 eV, with conduction and valence band levels that are primarily derived from the Re d0 and Cu d10 orbitals, respectively, and mixed with O p-orbital contributions. In contrast to the silver rhenates, which have relatively lower energy Ag d10 orbitals, the inclusion of the organic ligands into the structures has only a very minor effect ( approximately 0.1 eV) on the band gap size. The optical absorptions, in combination with the air-stable open-framework layered structures, illustrate that heterometallic Cu1+/Re7+ oxides can be promising candidates for investigating in visible-light photocatalytic reactions.}, number={4}, journal={INORGANIC CHEMISTRY}, author={Lin, Haisheng and Maggard, Paul A.}, year={2007}, month={Feb}, pages={1283–1290} }
 @article{yan_olmstead_maggard_2007, title={Effect of Spin-Ladder Topology on 2D Charge Ordering:  Toward New Spin-Antiferroelectric Transitions}, volume={129}, ISSN={0002-7863 1520-5126}, url={http://dx.doi.org/10.1021/ja0754709}, DOI={10.1021/ja0754709}, abstractNote={The low-temperature structures of M(pyz)V4O10 (M = Co, Zn) in the spin-gapped state have been investigated by single-crystal X-ray diffraction and electronic structure calculations and provide evidence for a new type of spin-antiferroelectric transition for M = Zn. This new type of phase transition involves the onset of charge ordering within spin ladders that can be mediated by the metal-organic chains via a modification of the inter-ladder interactions.}, number={42}, journal={Journal of the American Chemical Society}, publisher={American Chemical Society (ACS)}, author={Yan, Bangbo and Olmstead, Marilyn M. and Maggard, Paul A.}, year={2007}, month={Oct}, pages={12646–12647} }
 @article{zhang_maggard_2007, title={Investigation of photocatalytically-active hydrated forms of amorphous titania, TiO2·nH2O}, volume={186}, ISSN={1010-6030}, url={http://dx.doi.org/10.1016/j.jphotochem.2006.07.004}, DOI={10.1016/j.jphotochem.2006.07.004}, abstractNote={Low temperature preparations of hydrated forms of amorphous titania, TiO2·nH2O, have been obtained starting from Ti(n-butoxide)4 in ethanol, acetone, hexane or tetrahydrofuran solutions by either slow evaporation (TiO2–A1) or from rapid precipitation in an aqueous HCl solution using ammonia (TiO2–A2). The washed products lost/reabsorbed water up to a maximum of 19 wt.% for samples of TiO2–A1 (n ∼ 1.0) and 9.9% for TiO2–A2 (n ∼ 0.5), determined from TGA, and exhibited an optical band gap of ∼3.5 eV. Under full spectrum irradiation in aqueous methanol solutions the photocatalytic rates for H2 production reached a maximum of 314 and 1158 μmol h−1 g−1 for bare and platinized (0.5 wt.%) samples of TiO2–A1, respectively, and 210 and 170 μmol h−1 g−1 for TiO2–A2. The photocatalytic rates measured at a slightly elevated temperature of 58 °C were up to 2× greater than those measured nearer room temperature, while these rates were independent of the amount or type of solvent used in their preparation. The UV–vis diffuse reflectances, post irradiation, indicate a higher concentration of Ti3+ sites in TiO2–A1 compared to TiO2–A2, and thus a higher density of active sites and reduced electron–hole recombination.}, number={1}, journal={Journal of Photochemistry and Photobiology A: Chemistry}, publisher={Elsevier BV}, author={Zhang, Zhenyu and Maggard, Paul A.}, year={2007}, month={Feb}, pages={8–13} }
 @inbook{maggard_yan_2007, place={Weinheim, Germany}, title={Layered Perrhenate and Vanadate Hybrid Solids: On the Utility of Structural Relationships}, ISBN={9783527609932 9783527315109}, url={http://dx.doi.org/10.1002/9783527609932.ch17}, DOI={10.1002/9783527609932.ch17}, abstractNote={This chapter contains sections titled: Introduction Heterometallic Perrhenates Background: Molecular and Condensed Metal-perrhenates Copper- and Silver-perrhenate Hybrids Metal-coordinated Pillars in Perrhenate Hybrids Heterometallic Vanadates Background: Layered Vanadate Species Layered Heterometallic Vanadates: Charge Density Matching Heterometallic Reduced Layered Vanadates Conclusions Acknowledgments References}, booktitle={Inorganic Chemistry in Focus III}, publisher={Wiley-VCH Verlag GmbH & Co. KGaA}, author={Maggard, Paul A. and Yan, Bangbo}, editor={Meyer, G. and Naumann, D. and Wesemann, L.Editors}, year={2007}, month={Jan}, pages={251–266} }
 @article{yan_maggard_2007, title={M(bipyridine)V4O10 (M = Cu, Ag): Hybrid analogues of low-dimensional reduced vanadates}, volume={46}, ISSN={["1520-510X"]}, DOI={10.1021/ic700729q}, abstractNote={New hybrid layered vanadates, M(bpy)V4O10 (I, M = Cu+; II, M = Ag+; bpy = 4,4'-bipyridine), were prepared from hydrothermal reactions at 220-230 degrees C, and their structures were characterized by single-crystal X-ray diffraction [I, P21/c (No. 14), Z = 4, a = 3.6154(3) A, b = 21.217(1) A, c = 20.267(1) A, and beta = 90.028(3) degrees ; II, P (No. 2), Z = 2, a = 3.5731(4) A, b = 10.429(1) A, c = 21.196(2) A, alpha = 89.031(5) degrees , beta = 89.322(5) degrees , and gamma = 85.546(5) degrees ]. The structures of I and II are closely related, though not isostructurally, with both containing partially reduced V4O10- layers that are constructed from zigzag chains of edge-sharing VO5 tetragonal pyramids. Neighboring zigzag chains within a layer condense via shared vertices and alternate between versions containing V4.5+ and V5+ ions, such that two out of four symmetry-unique V atoms are reduced by a half-electron on average. The interlayer spaces contain unusual M(bpy)+ chains formed from the coordination of two bridging bpy ligands to Ag+/Cu+ in a nearly linear fashion and each with a third bond to a single apical O atom of the reduced (V4.5+) VO5 tetragonal pyramids. Both I and II are stable until approximately 350-400 degrees C in O2, at which point the ligands are liberated to yield the purely inorganic MxV4O10 (M = Ag, Cu) solids. The electrical conductivities of both compounds show a temperature dependence that is consistent with Mott's variable-range-hopping model for randomly localized electrons. Magnetic susceptibilities of both I and II can be fitted to a Curie-Weiss expression (theta = -25 and -31 K, respectively; C approximately 0.40 emu.mol-1.K for both) at higher temperatures and one unpaired spin per formula. However, at below approximately 12-18 K, both show evidence for an antiferromagnetic transition that can be fitted well to the Heisenberg linear antiferromagnetic chain model. These results are analyzed with respect to related reduced vanadates and help to provide new structure-property insights for strongly correlated electron systems.}, number={16}, journal={INORGANIC CHEMISTRY}, author={Yan, Bangbo and Maggard, Paul A.}, year={2007}, month={Aug}, pages={6640–6646} }
 @article{porob_maggard_2006, title={Flux syntheses of La-doped NaTaO3 and its photocatalytic activity}, volume={179}, ISSN={["1095-726X"]}, DOI={10.1016/j.jssc.2006.03.008}, abstractNote={The La-doped (2%) NaTaO3 perovskite-type solid was synthesized in high purity and homogeneity within a molten Na2SO4/K2SO4 (1:1 molar ratio) flux in much shortened reaction times, 0.5–1.0 h, compared to conventional solid-state techniques. The particle morphologies were investigated by scanning electron microscopy and were irregular block-shaped with dimensions of 500–100 nm and smaller surface features. The bulk particle sizes were found to decrease with increasing amounts of flux used in the synthesis, from 1:1 (NaTaO3:flux), 1:2 to 1:3 for a reaction duration of 1 h. Photocatalytic activities of the NaTaO3 products were measured in an aqueous methanol solution to be 535–1115 μmol H2 h−1 g−1, and which increased with increasing particle sizes and decreasing amounts of flux used in the synthesis. These rates were up to ×2 greater than that measured for a conventionally prepared La-doped (2%) NaTaO3 sample, which is currently one of the most efficient UV-photocatalysts known.}, number={6}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Porob, Digamber G. and Maggard, Paul A.}, year={2006}, month={Jun}, pages={1727–1732} }
 @article{luo_maggard_2006, title={Hydrothermal Synthesis and Photocatalytic Activities of SrTiO3-Coated Fe2O3 and BiFeO3}, volume={18}, ISSN={0935-9648 1521-4095}, url={http://dx.doi.org/10.1002/adma.200500109}, DOI={10.1002/adma.200500109}, abstractNote={The photocatalysis of H 2 O into H 2 and O 2 via aqueous suspensions of metal-oxide powders has drawn increasing attention in recent years, as noted in several reviews. [1–3] Numerous solids (> 30) reportedly exhibit high quantum efficiencies (QEs) for H 2 O photocatalysis at ultraviolet wavelengths, including NaTaO 3 (56% QE), [4] Sr 2 Nb 2 O 7 (23%), [5] La 2 Ti 2 O 7 (27%), [6] and La 4 CaTi 5 O 17 (20%). [5a] The metal oxides are typically loaded with co-catalysts on their surfaces, such as Pt, NiO, or RuO 2 , as active sites for H 2 and/or O 2 production, and display catalytic rates that are stable for hundreds of hours and longer time spans. Contrasted to this has been the relative failure to obtain efficient photocatalysis for the visible (400–700 nm) and predominant region of the solar spectrum, as reported for a -Fe 2 O 3 ( ∼ 2%) or In 1– x Ni x TaO 4 (0.66%), [7,8] though the theoretical requirement for H 2 O → H 2 + 1/2 O 2 is k ≤ 1008 nm. [9] One limiting barrier is the requirement for a metal oxide to have a bandgap appropriate for the absorption of visible light ( ≤ 3.0 eV), while also having a conduction band edge, or flat-band potential, above the potential of the H 2 /H 2 O redox couple. [9,10] Empirical relationships have been formulated that predict a visible-light bandgap can only be obtained at the expense of high conduction band levels (with a few exceptions) in transition-metal oxides (e.g., E fb =2.94 – E g ; E fb = flat band potential, and must be <}, number={4}, journal={Advanced Materials}, publisher={Wiley}, author={Luo, J. and Maggard, P. A.}, year={2006}, month={Feb}, pages={514–517} }
 @article{yan_maggard_2006, title={Polar Symmetry and Intercalation of New Multilayered Hybrid Molybdates:  [M2(pzc)2(H2O)x][Mo5O16] (M = Co, Ni)}, volume={45}, ISSN={0020-1669 1520-510X}, url={http://dx.doi.org/10.1021/ic060253e}, DOI={10.1021/ic060253e}, abstractNote={The layered molybdate [M2(pzc)2(H2O)x][Mo5O16] (I: M = Ni, x = 5.0; II: M = Co, x = 4.0; pzc = pyrazinecarboxylate) hybrid solids were synthesized via hydrothermal reactions at 160-165 degrees C. The structures were determined by single-crystal X-ray diffraction data for I (Cc, Z = 4; a = 33.217(4) A, b = 5.6416(8) A, c = 13.982(2) A, beta = 99.407(8) degrees , and V = 2585.0(6) A3) and powder X-ray diffraction data for II (C2/c, Z = 4; a = 35.42(6) A, b = 5.697(9) A, c = 14.28(2) A, beta = 114.95(4) degrees , and V = 2614(12) A3). The polar structure of I contains new [Ni2(pzc)2(H2O)5]2+ double layers that form an asymmetric pattern of hydrogen bonds and covalent bonds to stair-stepped [Mo5O16]2- sheets, inducing a net dipole moment in the latter. In II, however, the [Co2(pzc)2(H2O)4]2+ double layers have one less coordinated water and subsequently exhibit a symmetric pattern of covalent and hydrogen bonding to the [Mo5O16]2- sheets, leading to a centrosymmetric structure. Thermogravimetric analyses and powder X-ray diffraction data reveal that I can be dehydrated and rehydrated with from 0 to 6.5 water molecules per formula unit, which is coupled with a corresponding contraction/expansion of the interlayer distances. Also, the dehydrated form of I can be intercalated by approximately 4.3 H2S molecules per formula unit, but the intercalation by pyridine or methanol is limited to less than one molecule per formula unit.}, number={12}, journal={Inorganic Chemistry}, publisher={American Chemical Society (ACS)}, author={Yan, Bangbo and Maggard, Paul A.}, year={2006}, month={Jun}, pages={4721–4727} }
 @article{yan_luo_dube_sefat_greedan_maggard_2006, title={Spin-Gap Formation and Thermal Structural Studies in Reduced Hybrid Layered Vanadates}, volume={45}, ISSN={0020-1669 1520-510X}, url={http://dx.doi.org/10.1021/ic0604563}, DOI={10.1021/ic0604563}, abstractNote={Reduced layered M(C4H4N2)V4O10 ((I, M = Co; II, M = Ni; III, M = Zn); C4H4N2 = pyrazine, pyz) hybrid solids were synthesized via hydrothermal reactions at 200-230 degrees C, and their structures determined by single-crystal X-ray diffraction (Cmcm, No. 63, Z = 4; a = 14.311(2), 14.2372(4), 14.425(1) A; b = 6.997(1), 6.9008(2), 6.9702(6) A; and c = 11.4990(8), 11.5102(3), 11.479(1) A; for I, II, and III, respectively). All three solids are isostructural and contain V4O102- layers condensed from edge- and corner-shared VO5 square pyramids. A single symmetry-unique V atom is reduced by 1/2 electron (on average) and bonds via its apical oxygen atom to interlayer Mpyz2+ chains. Magnetic susceptibility measurements show a strong temperature dependence and a Curie constant that is consistent with two randomly localized spins per V4O10(2-) formula for III. Further, the unusual discovery of a remarkably well-defined transition to a singlet ground state, as well as formation of a spin gap, is found for III at 22(1) K. The temperature-dependent electrical conductivities show apparent activation energies of 0.36 (I), 0.46 (II), and 0.59 eV (III). During heating cycles in flowing N2, the samples exhibit weight losses corresponding to the removal of predominantly pyrazine, pyrazine fragments, and CO2 via reaction of pyrazine with the vanadate layer. The complete removal of pyrazine without loss of crystallinity is found for well-ground samples of I and III. The SEM images of I and II after heating at 400-500 degrees C show relatively intact crystals, but at 600 degrees C further structural collapse results in the formation of macropores at the surfaces.}, number={13}, journal={Inorganic Chemistry}, publisher={American Chemical Society (ACS)}, author={Yan, Bangbo and Luo, Junhua and Dube, Paul and Sefat, Athena S. and Greedan, John E. and Maggard, Paul A.}, year={2006}, month={Jun}, pages={5109–5118} }
 @article{lin_yan_boyle_maggard_2006, title={Synthesis and Properties of Pyrazine-Pillared Ag3Mo2O4F7 and AgReO4 Layered Phases}, volume={179}, ISSN={["1095-726X"]}, DOI={10.1016/j.jssc.2005.10.037}, abstractNote={The new pyrazine-pillared solids, AgReO4(C4H4N2) (I) and Ag3Mo2O4F7(C4H4N2)3 (C4H4N2=pyrazine, pyz) (II), were synthesized by hydrothermal methods at 150 °C and characterized using single crystal X-ray diffraction (I—P21/c, No. 14, Z=4, a=7.2238(6) Å, b=7.4940(7) Å, c=15.451(1) Å, β=92.296(4)°; II—P2/n, No. 13, Z=2, a=7.6465(9) Å, b=7.1888(5) Å, c=19.142(2) Å, β=100.284(8)°), thermogravimetric analysis, UV-Vis diffuse reflectance, and photoluminescence measurements. Individual Ag(pyz) chains in I are bonded to three perrhenate ReO4– tetrahedra per layer, while each layer in II contains sets of three edge-shared Ag(pyz) chains (π–π stacked) that are edge-shared to four Mo2O4F73– dimers. A relatively small interlayer spacing results from the short length of the pyrazine pillars, and which can be removed at just slightly above their preparation temperature, at >150–175 °C, to produce crystalline AgReO4 for I, and Ag2MoO4 and an unidentified product for II. Both pillared solids exhibit strong orange-yellow photoemission, at 575 nm for I and 560 nm for II, arising from electronic excitations across (charge transfer) band gaps of 2.91 and 2.76 eV in each, respectively. Their structures and properties are analyzed with respect to parent ‘organic free’ silver perrhenate and molybdate solids which manifest similar photoemissions, as well as to the calculated electronic band structures.}, number={1}, journal={Journal of Solid State Chemistry}, author={Lin, H. and Yan, B. and Boyle, P.D. and Maggard, P}, year={2006}, pages={217–225} }
 @article{porob_maggard_2006, title={Synthesis of textured Bi5Ti3FeO15 and LaBi4Ti3FeO15 ferroelectric layered Aurivillius phases by molten-salt flux methods}, volume={41}, ISSN={["0025-5408"]}, DOI={10.1016/j.materresbull.2006.01.020}, abstractNote={The ferroelectric layered Bi5Ti3FeO15 and LaBi4Ti3FeO15 Aurivillius phases were synthesized in high purity and textured microstructures in a molten Na2SO4/K2SO4 (1:1 molar ratio) flux in much shortened reaction times, 1 h minimum compared to conventional techniques. The particle growth and microstructure of both phases were investigated as a function of temperature and reaction duration, and yielded plate-like particles that could be synthesized in sizes from <1 μm to >20 μm. The product crystallinity, purity and microstructures were characterized via powder X-ray diffraction and scanning electron microscopy. The UV–vis diffuse reflectance of the products were measured and analyzed with respect to the resultant particle sizes.}, number={8}, journal={MATERIALS RESEARCH BULLETIN}, author={Porob, Digamber G. and Maggard, Paul A.}, year={2006}, month={Aug}, pages={1513–1519} }
 @article{maggard_yan_luo_2005, title={Pillared hybrid solids with access to coordinatively unsaturated metal sites: An alternative strategy}, volume={44}, ISSN={["1521-3773"]}, DOI={10.1002/anie.200462715}, abstractNote={A layered effect: Replacement of pyrazine (A) with Co- or Ni-coordinated 2-pyrazinecarboxylate (pzc; B) between neutral AgReO4 layers (red and blue polyhedra) yields M(pzc)2(H2O)2AgReO4 (M=Co (shown) or Ni). This novel strategy is aimed at pillared solids with coordinated H2O that can be reversibly removed without causing structural collapse to give coordinatively unsaturated Ni and Co sites.}, number={17}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Maggard, PA and Yan, BB and Luo, JH}, year={2005}, pages={2553–2556} }
 @article{kopf_maggard_stern_poeppelmeier_2005, title={Poly[nickel(II)-di-μ-4,4′-bipyridyl-κ4N:N′-μ-dichromato-κ2O:O′] and poly[copper(II)-di-μ-4,4'-bipyridyl-κ4N:N′-μ-dichromato-κ2O:O′]}, volume={61}, ISSN={0108-2701}, url={http://dx.doi.org/10.1107/s0108270105001605}, DOI={10.1107/s0108270105001605}, abstractNote={The novel title hybrid isomorphous organic–inorganic mixed-metal dichromates, [Ni(Cr2O7)(C10H8N2)2] and [Cu(Cr2O7)(C10H8N2)2], have been synthesized. A non-centrosymmetric three-dimensional (4,6)-net is formed from a linear chain of vertex-linked [Cr2O{}_{7}]2− and [MN4O{}_{2}]2+ (M = Ni and Cu) units, which in turn are linked by the planar bidentate 4,4′-­bipyridine ligand through the four remaining vertices of the [MN4O{}_{2}]2+ octahedra. There are two such three-dimensional nets that interpenetrate with inversion symmetry.}, number={4}, journal={Acta Crystallographica Section C Crystal Structure Communications}, publisher={International Union of Crystallography (IUCr)}, author={Kopf, Amy L. and Maggard, Paul A. and Stern, Charlotte L. and Poeppelmeier, Kenneth R.}, year={2005}, month={Mar}, pages={m165–m168} }
 @article{yan_capracotta_maggard_2005, title={Structural origin of chirality and properties of a remarkable helically pillared solid}, volume={44}, ISSN={["1520-510X"]}, DOI={10.1021/ic050794o}, abstractNote={A new helically pillared and chiral solid, Cu(pzc)2AgReO4 (I, pzc = pyrazinecarboxylate), was synthesized from hydrothermal reactions at 95-125 degrees C. The structural origin of its chirality, relative to the achiral M(pzc)2(H2O)2AgReO4 (II, M = Co; III, M = Ni) analogues, arises from significantly tilted pillars and hydrogen bonds to the AgReO4 layers. The new pillared structure exhibits second harmonic generation activity, CO2 absorption, thermal stability to approximately 250 degrees C, and Curie-Weiss magnetism expected for isolated Cu2+.}, number={19}, journal={INORGANIC CHEMISTRY}, author={Yan, BB and Capracotta, MD and Maggard, PA}, year={2005}, month={Sep}, pages={6509–6511} }
 @inbook{maggard_2004, place={New York}, title={Inorganic Chemistry}, volume={2}, ISBN={9780028657233}, booktitle={Chemistry: Foundations and Applications}, publisher={Macmillan Reference USA}, author={Maggard, P}, editor={Lagowski, J.J.Editor}, year={2004} }
 @article{maggard_kopf_stern_poeppelmeier_2004, title={Probing Helix Formation in Chains of Vertex-Linked Octahedra}, volume={6}, ISSN={["1466-8033"]}, DOI={10.1039/b406621a}, abstractNote={The rational design of crystal structures based on the chemical nature of molecular components, a longstanding and exciting research topic in organic solid state chemistry, is an emerging theme of crystal engineering in inorganic solid state chemistry. In particular, noncentrosymmetric structures, or those lacking inversion symmetry, are important for future technologies that are based on piezoelectricity, pyroelectricity, ferroelectricity and second harmonic generation (SHG). Materials that exhibit these properties provide a large and new class of solids for studies in basic science associated with the noncentrosymmetric (chiral, polar, or chiral–polar) space groups. Structures comprised of vertex-linked octahedra are common in inorganic solids. The subject of our Highlight is the rational synthesis of linear, zigzag or helical chains when two vertices of an octahedron, which are either adjacent (cis) or opposite (trans), are linked.}, number={Sep 17 2004}, journal={CrystEngComm}, author={Maggard, P.A. and Kopf, A.L. and Stern, C.L. and Poeppelmeier, K.R.}, year={2004}, pages={452–457} }
 @article{luo_alexander_wagner_maggard_2004, title={Synthesis and characterization of ReO4-containing microporous and open framework structures}, volume={43}, ISSN={["1520-510X"]}, DOI={10.1021/ic049609h}, abstractNote={A microporous and an open framework structure, [Cu(2)(pzc)(2)(H(2)O)(2)ReO(4)] (I) and [Cu(pzc)(H(2)O)ReO(4)].2H(2)O (II) (pzc = 2-pyrazinecarboxylate), respectively, have been prepared using hydrothermal methods and characterized using IR, TGA, and X-ray diffraction (I Pnma, No. 62, Z = 4, a = 7.4949(9) A, b = 24.975(3) A, c = 9.141(1) A; II P2(1)/c, No. 14, Z = 4, a = 8.5878(9) A, b = 12.920(1) A, c = 9.741(1) A, beta = 92.830(2) degrees ). I and II crystallize as red and blue solids, respectively, and each contains chains constructed from alternating Cu(pzc)(2)/ReO(4) oxide-bridged metal sites. The bidentate pzc ligand further bridges each -Cu-O-Re-O- chain to adjacent chains, via the Cu sites, to form a 3D net in I, with ellipsoidal channels that are approximately 3.3-4.7 A x 12.5 A, and in II, stacked layers of square nets with H(2)O-filled cavities that are approximately 4.4 x 5.1 A. Local ReO(4)(-) groups, a component of common oxidation catalysts, are directed at the channels and cavities of each structure, respectively. Thermogravimetric analysis indicates that I loses up to 64% of its H(2)O content before decomposition at 225 degrees C, while II loses approximately 100% of its H(2)O content by 265 degrees C.}, number={18}, journal={INORGANIC CHEMISTRY}, author={Luo, JH and Alexander, B and Wagner, TR and Maggard, PA}, year={2004}, month={Sep}, pages={5537–5542} }
 @article{maggard_corbett_2004, title={Two-Dimensional Metallic Chain Compounds Y5M2Te2(M = Fe, Co, Ni) That Are Related to Gd3MnI3. The Hydride Derivative Y5Ni2Te2D0.4}, volume={43}, ISSN={0020-1669 1520-510X}, url={http://dx.doi.org/10.1021/ic0303136}, DOI={10.1021/ic0303136}, abstractNote={Y(5)M(2)Te(2) (M = Fe, Co, Ni) have been prepared by high-temperature solid-state techniques and shown to be isostructural and orthorhombic Cmcm (No. 63), Z = 4. The structure was established by single crystal X-ray methods at 23 degrees C for M = Fe, with a = 3.9594(3) A, b = 15.057(1) A, and c = 15.216(1) A. The new structure contains zigzag chains of the late transition metal sheathed by a column of yttrium atoms that are in turn condensed through trans vertices on the latter to yield 2D bimetallic layers separated by single layers of tellurium atoms. Reaction of hydrogen with Y(5)Ni(2)Te(2) causes a rumpling of the Y-Ni layers as determined by both single X-ray crystal means at 23 degrees C and neutron powder diffraction at -259 degrees C for Y(5)Ni(2)Te(2)D(0.41(1)), Pnma (No. 62), Z = 4. Lattice constants from the former study are a = 14.3678(7) A, b = 4.0173(2) A, and c = 15.8787(7) A. The hydrogen is accommodated in tetrahedral yttrium cavities generated by bending the formerly flat sheets at the trans Y vertices. A higher hydride version also exists. Band structure calculations confirm the 2D metal-bonded character of the compounds and also help illustrate the bonding/matrix changes that accompany the bonding of hydrogen. The ternary structures for both Y(5)M(2)Te(2) and Sc(5)Ni(2)Te(2) can be derived from that of Gd(3)MnI(3), the group illustrating three different kinds of metal chain condensation.}, number={8}, journal={Inorganic Chemistry}, publisher={American Chemical Society (ACS)}, author={Maggard, Paul A. and Corbett, John D.}, year={2004}, month={Apr}, pages={2556–2563} }
 @article{maggard_nault_stern_poeppelmeier_2003, title={Alignment of acentric MoO3F33- anions in a polar material: (Ag3MoOT3F3(Ag3MoO4)Cl}, volume={175}, ISSN={["1095-726X"]}, DOI={10.1016/S0022-4596(03)00090-2}, abstractNote={(Ag3MoO3F3)(Ag3MoO4)Cl was synthesized by hydro(solvato)thermal methods and characterized by single-crystal X-ray diffraction (P3m1, No. 156, Z=1, a=7.4488(6)Å, c=5.9190(7) Å). The transparent colorless crystals are comprised of chains of distorted fac-MoO3F33− octahedra and MoO42− tetrahedra anions, as suggested by the formulas Ag3MoO3F3 and Ag3MoO4+, and are connected through Ag+ cations in a polar alignment along the c-axis. One Cl− anion per formula unit serves as a charge balance and connects the two types of chains in a staggered fashion, offset by ∼12×c. In MoO42−, the Mo atom displaces towards a single oxide vertex, and in MoO3F33−, the Mo displaces towards the three oxide ligands. The ordered oxide–fluoride ligands on the MoO3F33− anion is important to prevent local inversion centers, while the polar organization is directed by the Cl− anion and interchain dipole–dipole interactions. The dipole moments of MoO3F33− and MoO42− align in the negative c-axis direction, to give a polar structure with no cancellation of the individual moments. The direction and magnitude of the dipole moments for MoO3F33− and MoO42− were calculated from bond valence analyses and are 6.1 and 1.9 debye (10−18 esu cm) respectively, compared to 4.4 debye for polar NbO6 octahedra in LiNbO3, and 4.5 debye for polar TiO6 octahedra in KTiOPO4 (KTP).}, number={1}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Maggard, PA and Nault, TS and Stern, CL and Poeppelmeier, KR}, year={2003}, month={Oct}, pages={27–33} }
 @article{maggard_boyle_2003, title={Synthesis and properties of V6O16CU(C4H4N2)(2)(.)(H2O)(0.22(1)): Charge density matching of a metal-segregated layer structure}, volume={42}, ISSN={["0020-1669"]}, DOI={10.1021/ic0342649}, abstractNote={A metal-segregated layered compound, containing square nets of Cu(pyz)(2)(2+) and buckled V(6)O(16)(2)(-) layers, has been synthesized using hydrothermal techniques to have the composition V(6)O(16)Cu(C(4)H(4)N(2))(2) x (H(2)O)(0.22(1)) (C(4)H(4)N(2) = pyrazine, pyz). The Cu(II) square nets are nearly regular and undergo an antiferromagnetic transition at 8 K. In contrast to the plethora of recently synthesized metal-oxide clusters, chains, and networks in the VO(x)/M/L (M = late transition element; L = organonitrogen ligand) system, this compound is a relatively rare example that contains two different metals distributed into distinct layers. An application of charge density matching to form layered structures is postulated.}, number={14}, journal={INORGANIC CHEMISTRY}, author={Maggard, PA and Boyle, PD}, year={2003}, month={Jul}, pages={4250–4252} }
 @article{maggard_kopf_stern_poeppelmeier_2002, title={(2,2′-Bipyridine-κ2N,N′)(dichromato-κO)copper(II)}, volume={58}, ISSN={0108-2701}, url={http://dx.doi.org/10.1107/s0108270101021722}, DOI={10.1107/s0108270101021722}, abstractNote={The title compound, [Cu(Cr(2)O(7))(C(10)H(8)N(2))(2)], a new mixed-metal molecular compound, contains isolated molecular units, each comprised of one Cu(II) atom coordinated to two 2,2'-bipyridine ligands and also to an oxygen vertex of a dichromate anion. The Cu(II) atom has an approximate trigonal-bipyramidal geometry, which is consistent with previous studies. Both enantiomers of the chiral complex molecule are present and are related by inversion centers. In a reported pyridine analogue, achiral [Cu(Cr(2)O(7))(pyridine)(4)] chains pack in the non-centrosymmetric space group Pna2(1). Differences in the organic ligands influence the chirality and dimensionality of the Cu-Cr(2)O(7) bonding.}, number={4}, journal={Acta Crystallographica Section C Crystal Structure Communications}, publisher={International Union of Crystallography (IUCr)}, author={Maggard, Paul A. and Kopf, Amy L. and Stern, Charlotte L. and Poeppelmeier, Kenneth R.}, year={2002}, month={Mar}, pages={m207–m209} }
 @article{maggard_kopf_stern_poeppelmeier_ok_halasyamani_2002, title={From Linear Inorganic Chains to Helices:  Chirality in the M(pyz)(H2O)2MoO2F4(M = Zn, Cd) Compounds}, volume={41}, ISSN={0020-1669 1520-510X}, url={http://dx.doi.org/10.1021/ic0255712}, DOI={10.1021/ic0255712}, abstractNote={Cd(C(4)H(4)N(2))(H(2)O)(2)MoO(2)F(4) (C(4)H(4)N(2) = pyrazine, pyz) was synthesized via hydro(solvato)thermal methods and characterized by single-crystal X-ray diffraction methods (P3(2)()21, no. 154, Z = 3, a = 7.4328(7) A, c = 16.376(2) A). Both of the known M(pyz)(H(2)O)(2)MoO(2)F(4) (M = Zn, Cd) compounds are comprised of trans-M(pyz)(2)(OH(2))(2)F(2) and cis-MoO(2)F(4) octahedra that share fluoride vertices to form helical chains along the 3-fold screw axes. Individual chains are bridged to six symmetry-equivalent helices through metal-pyrazine and OH(2)...F and OH(2)...O hydrogen bonds. Structural comparisons of similar oxyfluoride chains demonstrate that they can be varied from linear to helical through (1) the replacement of pyridine or pyrazine by H(2)O molecules and (2) the substitution of cis-directing MoO(2)F(4)(2-) anions in place of trans-directing WO(2)F(4)(2-) or TiF(6)(2-) anions. Infrared absorption (IR) measurements for M = Cd show two distinct O-H stretches corresponding to hydrogen-bonded O-H...F and O-H...O groups. Contrastingly for M = Zn, IR measurements exhibit O-H stretches for averaged hydrogen-bonded O-H...(O/F) groups, free (unbound) O-H groups, and higher energy Mo-F stretches. The IR data suggest a small fraction of the O-H...F hydrogen bonds are broken in the M = Zn analogue as a result of the racemic twinning. Both compounds exhibit nonlinear optical behavior, with second harmonic generation (SHG) intensities, relative to SiO(2), of approximately 0.25 ( = 0.28 pm/V) for the racemically twinned Zn(pyz)(H(2)O)(2)MoO(2)F(4) and approximately 1.0 ( = 0.55 pm/V) for the enantiopure Cd(pyz)(H(2)O)(2)MoO(2)F(4).}, number={19}, journal={Inorganic Chemistry}, publisher={American Chemical Society (ACS)}, author={Maggard, Paul A. and Kopf, Amy L. and Stern, Charlotte L. and Poeppelmeier, Kenneth R. and Ok, Kang Min and Halasyamani, P. Shiv}, year={2002}, month={Sep}, pages={4852–4858} }
 @article{maggard_corbett_2001, title={Formation of Gallium Dimers in the Intermetallic Compounds R5Ga3(R = Sc, Y, Ho, Er, Tm, Lu). Deformation of the Mn5Si3-Type Structure}, volume={40}, ISSN={0020-1669 1520-510X}, url={http://dx.doi.org/10.1021/ic0011720}, DOI={10.1021/ic0011720}, abstractNote={The R(5)Ga(3) (R = Sc, Y, Ho, Er, Tm, Lu) phases were prepared by high-temperature solid-state techniques. The structure of monoclinic Sc(5)Ga(3) was determined by single-crystal X-ray diffraction means (C2/m, No. 12, Z = 4, a = 8.0793(5) A, b = 14.003(1) A, c = 5.9297(3) A, beta = 90.994(5) degrees ), and those of the isotypic R(5)Ga(3), R = Y, Ho, Er, Tm, Lu, were determined by Guinier powder diffraction. The new Sc(5)Ga(3) structure is a deformation of the hexagonal Mn(5)Si(3) type (P6(3)/mcm) and contains two types of gallium dimers with d(Ga-Ga) = 2.91 and 3.14 A. The closely spaced Sc1 chains in the parent Mn(5)Si(3) type transform to zigzag chains in concert with displacements of the uniformly spaced gallium atoms to form dimers within distorted confacial square antiprisms of Sc. Matrix effects appear important in the different Ga(2) bond lengths. Electronic calculations reveal that the transformation from the hypothetical Mn(5)Si(3) to the Sc(5)Ga(3) type is aided by antibonding Ga-Ga interactions between the dimers that are pushed above E(F) and Ga-Ga and Ga-Sc bonding states just below E(F) that are stabilized. Sc(5)Ga(3) is appropriately metallic. Except for R = Sc, Lu, the arc-melted R(5)Ga(3) compounds above slowly transform on annealing at 1150 degrees C and below into tetragonal Ba(5)Si(3)-type structures.}, number={6}, journal={Inorganic Chemistry}, publisher={American Chemical Society (ACS)}, author={Maggard, Paul A. and Corbett, John D.}, year={2001}, month={Mar}, pages={1352–1357} }
 @article{maggard_knight_corbett_2001, title={Substitutional chemistry in Mn5Si3-type scandium–main group compounds and the formation of quasibinary phases}, volume={315}, ISSN={0925-8388}, url={http://dx.doi.org/10.1016/s0925-8388(00)01266-4}, DOI={10.1016/s0925-8388(00)01266-4}, abstractNote={Abstract The compositions Sc5M3−xM′x (M=Al or Ga; M′=Sn, Sb or Te) were prepared by high-temperature solid-state techniques, and their Mn5Si3-type structures were either identified by powder X-ray means or determined by single crystal X-ray diffraction (hexagonal P63/mcm (No. 193), Z=2). Each Al or Ga (M) atom type exhibits mixed occupancy with Sn, Sb, or Te (M′) over different composition regions. For systems annealed at 1100–1575°C, single crystal data indicate that the phase widths of Sc5M3−xM′x extend over the ranges x=1.38(6)–2.25(2), 0.83(1)–0.96(1), 0–2.25(6), and 0–1.25(3) for Al/Sb, Al/Te, Ga/Sb, and Ga/Te, respectively. Powder X-ray data on the Sn systems shows phase width ranges of x=∼1.2–3.0 with Al and 0.0–3.0 with Ga, respectively. No interstitials in the Mn5Si3-type host were seen. The series of mixed compounds illustrate regular effects of substitution of larger and electron-richer M′ atoms in the flexible structure. The lattice constant trends follow Vegard’s law, with natural increases of a (b) and V with increasing x, but with small and irregular changes in c. Physical property measurements show that many of the compounds display metallic characteristics, with positive temperature-dependent resistivity and Pauli-like paramagnetism. The structure of Sc5Sb3 is reassigned to the Y5Bi3-type (Pnma).}, number={1-2}, journal={Journal of Alloys and Compounds}, publisher={Elsevier BV}, author={Maggard, Paul A. and Knight, Douglas A. and Corbett, John D.}, year={2001}, month={Feb}, pages={108–117} }
 @article{maggard_stern_poeppelmeier_2001, title={Understanding the Role of Helical Chains in the Formation of Noncentrosymmetric Solids}, volume={123}, ISSN={0002-7863 1520-5126}, url={http://dx.doi.org/10.1021/ja016055y}, DOI={10.1021/ja016055y}, abstractNote={A general, new principle for the design of noncentrosymmetric solids is evident in the packing of helical metal -oxyfluoride chains in Zn(C4H4N2)(H2O)2MoO2F4 (C4H4N2 ) pyrazine, pyz). Each inorganic helical chain comprises alternating Znand Mocentered octahedra and interleaves with six more helices of the same handedness through Zn -pyrazine-Zn bridges. From comparisons with similar structures which are centrosymmetric, the small organic ligand, pyrazine, plays a key role in the acentric packing of inorganic helices, while the cis-MoO2F4 and transZn(pyz)2(H2O)2F2 metal coordination geometries are important for helix formation. Major efforts in solid-state chemistry have as their goal the ability to engineer new inorganic frameworks that will yield desired physical properties. For instance, the designed synthesis of noncentrosymmetric solids is a challenging problem for the future fabrication of materials with ferroelectric, pyroand piezoelectric, and other nonlinear optical (NLO) properties. 1}, number={31}, journal={Journal of the American Chemical Society}, publisher={American Chemical Society (ACS)}, author={Maggard, Paul A. and Stern, Charlotte L. and Poeppelmeier, Kenneth R.}, year={2001}, month={Aug}, pages={7742–7743} }
 @article{maggard_corbett_2000, title={Insights into Metal Framework Constructions from the Syntheses of New Scandium- and Yttrium-Rich Telluride Compounds:  Y5Ni2Te2and Sc6PdTe2}, volume={122}, ISSN={0002-7863 1520-5126}, url={http://dx.doi.org/10.1021/ja002875j}, DOI={10.1021/ja002875j}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTInsights into Metal Framework Constructions from the Syntheses of New Scandium- and Yttrium-Rich Telluride Compounds: Y5Ni2Te2 and Sc6PdTe2Paul A. Maggard and John D. CorbettView Author Information Department of Chemistry Iowa State University Ames, Iowa 50011 Cite this: J. Am. Chem. Soc. 2000, 122, 43, 10740–10741Publication Date (Web):October 13, 2000Publication History Received3 August 2000Published online13 October 2000Published inissue 1 November 2000https://doi.org/10.1021/ja002875jCopyright © 2000 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views257Altmetric-Citations25LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (189 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Chemical structure,Condensation,Metals,Palladium,Transition metals Get e-Alerts}, number={43}, journal={Journal of the American Chemical Society}, publisher={American Chemical Society (ACS)}, author={Maggard, Paul A. and Corbett, John D.}, year={2000}, month={Nov}, pages={10740–10741} }
 @article{maggard_corbett_2000, title={Sc6MTe2(M = Mn, Fe, Co, Ni):  Members of the Flexible Zr6CoAl2-Type Family of Compounds}, volume={39}, ISSN={0020-1669 1520-510X}, url={http://dx.doi.org/10.1021/ic0003269}, DOI={10.1021/ic0003269}, abstractNote={The compounds Sc6MTe2 (M = Mn, Fe, Co, Ni) have been prepared by high-temperature solid-state techniques and their structures determined to be hexagonal P62m (No. 189), Z = 1, a = 7.662(1) A, 7.6795(2) A, 7.6977(4) A, 7.7235(4) A and c = 3.9041(9) A, 3.8368(2) A, 3.7855(3) A, 3.7656(3) A for M = Mn, Fe, Co, and Ni, respectively. Crystal structures were refined for M = Fe and Ni, while M = Mn and Co were assigned as isostructural on the basis of powder diffraction data. The Sc6MTe2 compounds belong to a large family with the Zr6CoAl2-type structure, an ordered variant of the Fe2P structure. The structure contains confacial tricapped trigonal prisms of scandium centered alternately by the late transition metal or tellurium atoms. The Sc6MTe2 compounds are the electron-poorest examples of this structure type. Extended Hückel band calculations for M = Fe and Ni show that both compounds exhibit largely 1D metal-metal bonding and are predicted to be metallic.}, number={18}, journal={Inorganic Chemistry}, publisher={American Chemical Society (ACS)}, author={Maggard, Paul A. and Corbett, John D.}, year={2000}, month={Sep}, pages={4143–4146} }
 @article{maggard_corbett_2000, title={Sc9Te2:  A Two-Dimensional Distortion Wave in the Scandium-Richest Telluride}, volume={122}, ISSN={0002-7863 1520-5126}, url={http://dx.doi.org/10.1021/ja993316j}, DOI={10.1021/ja993316j}, abstractNote={Sc9Te2 was prepared by high-temperature solid-state techniques, and the structure was determined by single-crystal X-ray diffraction to be monoclinic, Cc (No. 9, Z = 8) with a = 7.7576(1) A, b = 15.654(3) A, c = 17.283(3) A, and β = 90.01(3)° at 23 °C. The structure of metallic Sc9Te2 can be viewed as columns built either from distorted 3 × 3 bcc metal atoms or from distorted edge-sharing octahedra along a that are joined via intercolumn bonds on opposite sides into two-dimensional layers along b. A corrugated layer of Te atoms separates the metal layers in the c direction. This structure derives from the Ti9Se2 structure, with doubled a and b dimensions and a lower symmetry. Magnetic susceptibility measurements on Sc9Te2 show a substantially temperature-independent paramagnetism that is much smaller per metal atom than those for other scandium-rich tellurides or scandium metal. Extended Huckel band calculations reveal a clear distinction between high overlap populations for Sc−Sc interactions in the in...}, number={5}, journal={Journal of the American Chemical Society}, publisher={American Chemical Society (ACS)}, author={Maggard, Paul A. and Corbett, John D.}, year={2000}, month={Feb}, pages={838–843} }
 @article{maggard_corbett_1999, title={Sc5Ni2Te2:  Synthesis, Structure, and Bonding of a Metal−Metal-Bonded Chain Phase, a Relative of Gd3MnI3}, volume={38}, ISSN={0020-1669 1520-510X}, url={http://dx.doi.org/10.1021/ic981073a}, DOI={10.1021/ic981073a}, abstractNote={Sc{sub 5}Ni{sub 2}Te{sub 2} has been prepared by high-temperature solid-state techniques and the structure determined at 23 C by single crystal and powder X-ray diffraction methods to be orthorhombic. The structure contains pairs of eclipsed zigzag chains of nickel atoms that are sheathed by scandium atoms and demarcated from other chains by tellurium atoms. The structure is isotypic with that of Hf{sub 5}Co{sub 1+x}P{sub 3{minus}x}, but shifted atomic positions and a different ordering of the main group and late transition elements give it a clearly 1D character. The differences in dimensionality, ordering, and bonding are discussed, and comparisons are made with Gd{sub 3}MnI{sub 3} and rare-earth-metal cluster halides in general.}, number={8}, journal={Inorganic Chemistry}, publisher={American Chemical Society (ACS)}, author={Maggard, Paul A. and Corbett, John D.}, year={1999}, month={Apr}, pages={1945–1950} }
 @article{maggard_corbett_1998, title={The Synthesis, Structure, and Bonding of Sc8Te3and Y8Te3. Cooperative Matrix and Bonding Effects in the Solid State}, volume={37}, ISSN={0020-1669 1520-510X}, url={http://dx.doi.org/10.1021/ic971107z}, DOI={10.1021/ic971107z}, abstractNote={Sc8Te3 and Y8Te3 have been prepared by high-temperature solid-state techniques. The structures of both were determined from single-crystal and powder X-ray diffraction methods to be monoclinic, C2/...}, number={4}, journal={Inorganic Chemistry}, publisher={American Chemical Society (ACS)}, author={Maggard, Paul A. and Corbett, John D.}, year={1998}, month={Feb}, pages={814–820} }
 @article{maggard_corbett_1997, title={Sc2Te: A Novel Example of Condensed Metal Polyhedra in a Metal-Rich but Relatively Electron-Poor Compound}, volume={36}, ISSN={0570-0833 1521-3773}, url={http://dx.doi.org/10.1002/anie.199719741}, DOI={10.1002/anie.199719741}, abstractNote={Condensed double chains of edge-sharing scandium octahedra are contained in Sc2Te. These structural units are augmented by more loosely bound pyramidal and zigzag scandium aggregates. On the right is a projection of these chains together with tellurium (the open circles). The metal array may be viewed as the result of the dissociation of the metal framework in electron-richer chalcogenides.}, number={18}, journal={Angewandte Chemie International Edition in English}, publisher={Wiley}, author={Maggard, Paul A. and Corbett, John D.}, year={1997}, month={Oct}, pages={1974–1976} }
 @article{lulei_maggard_corbett_1996, title={The Novel Encapsulation of Transition Metals in a Bioctahedral Rare Earth Metal Cluster: Cs2La10I17Co2}, volume={35}, ISSN={0570-0833 1521-3773}, url={http://dx.doi.org/10.1002/anie.199617041}, DOI={10.1002/anie.199617041}, abstractNote={A missing link in the chemistry of rare earth metal cluster compounds stabilized by interstitial transition metals is the new La10Co2 dimeric cluster shown on the right with its iodine environment. The most remarkable structural features of this cluster are the two edge-sharing La octahedra, each centered by a Co atom.}, number={15}, journal={Angewandte Chemie International Edition in English}, publisher={Wiley}, author={Lulei, Michael and Maggard, Paul A. and Corbett, John D.}, year={1996}, month={Aug}, pages={1704–1706} }
 @article{maggard_lobastov_schaefer_ewbank_ischenko_1995, title={Direct Evaluation of Equilibrium Molecular Geometries Using Real-Time Gas Electron Diffraction. 2. Selenium Hexafluoride}, volume={99}, ISSN={0022-3654 1541-5740}, url={http://dx.doi.org/10.1021/j100035a012}, DOI={10.1021/j100035a012}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDirect Evaluation of Equilibrium Molecular Geometries Using Real-Time Gas Electron Diffraction. 2. Selenium HexafluoridePaul Maggard, Vladimir A. Lobastov, Lothar Schaefer, John D. Ewbank, and Anatoli A. IschenkoCite this: J. Phys. Chem. 1995, 99, 35, 13115–13117Publication Date (Print):August 1, 1995Publication History Published online1 May 2002Published inissue 1 August 1995https://doi.org/10.1021/j100035a012RIGHTS & PERMISSIONSArticle Views43Altmetric-Citations16LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (387 KB) Get e-Alerts}, number={35}, journal={The Journal of Physical Chemistry}, publisher={American Chemical Society (ACS)}, author={Maggard, Paul and Lobastov, Vladimir A. and Schaefer, Lothar and Ewbank, John D. and Ischenko, Anatoli A.}, year={1995}, month={Aug}, pages={13115–13117} }