@article{chung_leonard_altoe_aloni_de yoreo_franzen_2013, title={The Formation of Pd Nanocrystals from Pd2(dba)3 Microcrystals}, volume={30}, number={3}, journal={Particle & Particle Systems Characterization}, author={Chung, S. and Leonard, D. N. and Altoe, V. and Aloni, S. and De Yoreo, J. J. and Franzen, S.}, year={2013}, pages={280–286} }
 @article{dhawan_du_batchelor_wang_leonard_misra_ozturk_gerhold_vo-dinh_2011, title={Hybrid Top-Down and Bottom-Up Fabrication Approach for Wafer-Scale Plasmonic Nanoplatforms}, volume={7}, ISSN={["1613-6810"]}, DOI={10.1002/smll.201002186}, abstractNote={Bridging the nanoscale level of probe fabrication and the megascale dimensions of sensor systems is one of the greatest challenges in the development of large-area plasmonic sensing platforms. We report a generalized hybrid nanofabrication approach combining top-down (deep-UV lithography) and bottom-up (controlled lateral epitaxial growth and atomic layer deposition) fabrication techniques for the development of nanostructured platforms. This technology allows the development of reproducible substrates with controlled sub-10 nm gaps between plasmonic nanostructures over an entire 6 inch wafer (1 inch ≈ 2.54 cm). By integrating soft matter (DNA probes) and hard matter (silicon nanochips), these}, number={6}, journal={SMALL}, author={Dhawan, Anuj and Du, Yan and Batchelor, Dale and Wang, Hsin-Neng and Leonard, Donovon and Misra, Veena and Ozturk, Mehmet and Gerhold, Michael D. and Vo-Dinh, Tuan}, year={2011}, month={Mar}, pages={727–731} }
 @article{leonard_franzen_2009, title={Is Pd-2(DBA)(3) a Feasible Precursor for the Synthesis of Pd Nanoparticles?}, volume={113}, ISSN={["1932-7447"]}, DOI={10.1021/jp903417r}, abstractNote={The organometallic reagent tris(dibenzylideneacetone) dipalladium(0) [Pd2(DBA)3] has been used as a reagent for synthesis of hexagonal microstructures ranging from 0.5−10 μm. We have shown elsewhere that Pd2(DBA)3 spontaneously forms hexagonal and cubic microstructures. The results obtained herein confirm that microstructures formed by spontaneous aggregation of Pd2(DBA)3 produce the same morphology and carbonaceous chemical composition as those produced with a process that has been called RNA-mediation by pyridyl-modified RNA (pmRNA). Synthesis products from both methods of preparation were analyzed using a combination of scanning transmission electron microscopy (STEM), electron energy loss spectroscopy, energy dispersive X-ray spectroscopy, and selected area electron diffraction. Indexing of electron diffraction patterns from hexagonal molecular crystals and metallic Pd nanoparticles combined with STEM Z-contrast imaging and X-ray dot maps were used to positively differentiate the two materials. On the...}, number={29}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Leonard, D. N. and Franzen, S.}, year={2009}, month={Jul}, pages={12706–12714} }
 @article{dhawan_muth_leonard_gerhold_gleeson_vo-dinh_russell_2008, title={Focused in beam fabrication of metallic nanostructures on end faces of optical fibers for chemical sensing applications}, volume={26}, ISSN={["1071-1023"]}, DOI={10.1116/1.3013329}, abstractNote={Focused ion beam (FIB) fabrication of fiber optic sensors, mainly chemical sensors, which are based on plasmonics-active nanostructures formed on the cleaved tips of optical fibers, is reported. The nanostructures fabricated included nanoholes in optically thick metallic films as well as metallic nanopillars and nanorods. The sensing mechanism is based on detecting shifts in surface plasmon resonances (SPRs) associated with nanoholes in metallic films and localized SPRs of metallic nanopillars and nanorods, when the refractive index of the medium surrounding the nanostructures is changed. These sensors can be employed for the detection of chemical agents in air as well as liquid media surrounding the sensors. FIB milling was employed to fabricate ordered arrays of nanoholes in optically thick (100–240nm) metallic films deposited on cleaved end faces of multimode, four-mode, and single-mode optical fibers. Separately, metallic nanorods and nanopillars were formed by first depositing a metallic (gold or silver) film on tips of optical fibers, which was followed by FIB milling large area patterns to form freestanding nanorods and nanopillars. Utilizing FIB allows engineering nanostructure geometries, i.e., nanostructure shapes and sizes that are chosen based on the plasmon resonances associated with them. Formation of periodic arrays of nanoholes provides a means of tuning plasmon resonance peaks, associated with extraordinary transmission of light through the array of nanoholes in the metallic films, based on periodicity and shape of the nanoholes as well as on refractive index changes to form sensitive chemical sensors.}, number={6}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Dhawan, A. and Muth, J. F. and Leonard, D. N. and Gerhold, M. D. and Gleeson, J. and Vo-Dinh, T. and Russell, P. E.}, year={2008}, month={Nov}, pages={2168–2173} }
 @article{leonard_cerruti_duscher_franzen_2008, title={Interfacial and solvent effects govern the formation of tris(dibenzylidenacetone)dipalladium(0) microstructures}, volume={24}, ISSN={["0743-7463"]}, DOI={10.1021/la801039j}, abstractNote={Organometallic palladium adducts have application as catalysts and as precursors for nanoparticle synthesis. Herein, we study the spontaneous formation of molecular crystals of the organometallic reagent tris(dibenzylidenacetone)dipalladium(0) (Pd(2)(DBA)(3)) in THF/H(2)O binary solvent systems. We report structural and chemical characterization of the resulting diverse structures with shapes including hexagonal platelets, rods, cubes, and stars. Optical microscopy, transmission electron microscopy, scanning electron microscopy, and energy-dispersive spectroscopy were used to determine representative structures and corresponding compositions when formed either in a binary solution or upon evaporation on a surface. The difference in Pd(2)(DBA)(3) particle morphology was attributed to differences in the surface tension of growing crystalline faces. The formation of a majority of rods or hexagonal platelets in solution was shown to be determined by the ratio of THF to H(2)O in the solvent, whereas supersaturation effects and interfacial surface tension played a major role in creating the shape of particles formed upon evaporation of Pd(2)(DBA)(3) droplets on a surface.}, number={15}, journal={LANGMUIR}, author={Leonard, Donovan N. and Cerruti, Marta and Duscher, Gerd and Franzen, Stefan}, year={2008}, month={Aug}, pages={7803–7809} }
 @article{darling_reynolds_leonard_duscher_scattergood_koch_2008, title={Self-assembled three-dimensional Cu-Ge nanoweb composite}, volume={19}, ISSN={["1361-6528"]}, DOI={10.1088/0957-4484/19/13/135603}, abstractNote={The inexpensive combination of cryogenically milled Cu3Ge powders sonochemically processed in a standard ultrasonic cleaner has led to the prototype of a heretofore undescribed class of material. This prototype is a nanostructured composite composed of 4.5 nm diameter Cu nanocrystals embedded in a three-dimensional (3D) amorphous CuGeO3 polyhedron web matrix. The diameters of the wires comprising the matrix are typically 5–15 nm. Complete structural and compositional characterization is reported to provide additional insight and firm designation on the observation of this previously undescribed class of material. The large surface to volume ratio of these nanoweb composites may offer unique advantages based on altered optical or electronic and magnetic properties. For example, quantum confinement of the Cu dots in the amorphous 3D nanowebs is possible. Nanostructures in general have altered properties compared to those of bulk materials and the same is expected in nanostructured composites.}, number={13}, journal={NANOTECHNOLOGY}, author={Darling, Kris A. and Reynolds, C. Lewis, Jr. and Leonard, Donovan N. and Duscher, Gerd and Scattergood, Ronald O. and Koch, Carl C.}, year={2008}, month={Apr} }
 @article{franzen_cerruti_leonard_duscher_2007, title={The role of selection pressure in RNA-mediated evolutionary materials synthesis}, volume={129}, ISSN={["0002-7863"]}, DOI={10.1021/ja076054r}, abstractNote={Evolutionary materials synthesis is a provocative concept that has the potential for the discovery of novel compounds ranging from drugs to inorganic materials. RNA-mediated evolutionary materials synthesis requires aqueous solvent of moderate ionic strength, water-soluble precursors, and an appropriately designed selection pressure. Throughout the selection process, the RNA must be folded, stable, and accessible once it has bound to a target, catalyzed a chemical reaction, or templated formation of a structure. Subsequently, the RNA must be accessible to permit reverse transcriptase to create DNA copies for amplification. A well-designed selection will generate RNAs that can favor growth of a particular crystal habit or catalyze a specific reaction pathway. In this study we rigorously test the assumptions, procedures, and results of the only published example of an RNA-mediated evolutionary materials synthesis. The proof that a particular RNA sequence is responsible for a novel material synthesis must be established by control experiments as outlined in the present study. Furthermore, the product of nanoscale synthesis must be studied using state-of-the-art characterization methods to determine that selection pressure is exerted according to design. Herein, we demonstrate the use of advanced electron microscopy to determine chemical composition and structure as a critical step in analysis of the success of a selection. We conclude that RNA selections should not be carried out in binary solvent systems, such as tetrahydrofuran (THF) and water. A specific example, which is not consistent with rigorous selection of functional RNAs or RNA cognates, is provided by the precipitation of the water-insoluble precursor, tris(dibenzylideneacetone) dipalladium(0) Pd2(DBA)3.}, number={49}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Franzen, Stefan and Cerruti, Marta and Leonard, Donovan N. and Duscher, Gerd}, year={2007}, month={Dec}, pages={15340–15346} }
 @article{cerruti_sauthier_leonard_liu_duscher_feldheim_franzen_2006, title={Gold and silica-coated gold nanoparticles as thermographic labels for DNA detection}, volume={78}, ISSN={["1520-6882"]}, DOI={10.1021/ac0600555}, abstractNote={The infrared emissivity of Au and silica-coated Au nanoparticles (Au NPs) deposited on indium tin oxide substrates was investigated. NPs were irradiated with laser light at a frequency close to the Au plasmon resonance band, and the blackbody radiation emitted as a result was monitored with an IR camera equipped with an InAs array detector. The differences in temperature before and after laser irradiation were recorded (T-jumps) and were found to be directly proportional to the number of particles present on the slide and to the laser power used in the experiment. Coating Au NPs with silica increased the measured T-jumps 2-5 times, depending on the thickness of the silica shell. This was in agreement with the observation that silica has a much higher IR emissivity than Au. Both Au and silica-coated Au NPs were then tested as labels for thermographic DNA detection. Target DNA concentrations as low as 100 pM were recorded when Au NPs were used as labels and as low as 10 pM when silica-coated Au NPs were used.}, number={10}, journal={ANALYTICAL CHEMISTRY}, author={Cerruti, Marta G. and Sauthier, Marc and Leonard, Donovan and Liu, Dage and Duscher, Gerard and Feldheim, Daniel L. and Franzen, Stefan}, year={2006}, month={May}, pages={3282–3288} }
 @article{rhodes_franzen_maria_losego_leonard_laughlin_duscher_weibel_2006, title={Surface plasmon resonance in conducting metal oxides}, volume={100}, ISSN={["1089-7550"]}, DOI={10.1063/1.2222070}, abstractNote={We report the initial observation of surface plasmon resonance (SPR) in a conducting metal oxide thin film. The SPR phenomenon has been observed by attenuated total reflection of near-infrared radiation and is in agreement with electron energy loss spectroscopy measurements. To date, only metals are known to exhibit surface plasmon resonance and only noble metals have practical application. According to theory SPR should be observable in any conductor. This theoretical prediction is verified in the present study. The compositions of many conducting metal oxides are systematically variable, suggesting a significant advance in thin film characterization and innovative possibilities for versatile and sensitive chemical sensing applications.}, number={5}, journal={JOURNAL OF APPLIED PHYSICS}, author={Rhodes, Crissy and Franzen, Stefan and Maria, Jon-Paul and Losego, Mark and Leonard, Donovan N. and Laughlin, Brian and Duscher, Gerd and Weibel, Stephen}, year={2006}, month={Sep} }
 @article{reddy_leonard_wiggins_jacob_2005, title={Internal displacement reactions in multicomponent oxides: Part I. Line compounds with narrow homogeneity range}, volume={36A}, ISSN={["1073-5623"]}, DOI={10.1007/s11661-005-0265-2}, abstractNote={As a model of an internal displacement reaction involving a ternary oxide “line” compound, the following reaction was studied at 1273 K as a function of time, t: Both polycrystalline and single-crystal materials were used as the starting NiTiO3 oxide. During the reaction, the Ni in the oxide compound is displaced by Fe and it precipitates as a γ-(Ni-Fe) alloy. The reaction preserves the starting ilmenite structure. The product oxide has a constant Ti concentration across the reaction zone, with variation in the concentration of Fe and Ni, consistent with ilmenite composition. In the case of single-crystal NiTiO3 as the starting oxide, the γ alloy has a “layered” structure and the layer separation is suggestive of Liesegang-type precipitation. In the case of polycrystalline NiTiO3 as the starting oxide, the alloy precipitates mainly along grain boundaries, with some particles inside the grains. A concentration gradient exists in the alloy across the reaction zone and the composition is >95 at. pct Ni at the reaction front. The parabolic rate constant for the reaction is k p =1.3 × 10−12 m2 s−1 and is nearly the same for both single-crystal and polycrystalline oxides.}, number={10}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Reddy, SNS and Leonard, DN and Wiggins, LB and Jacob, KT}, year={2005}, month={Oct}, pages={2685–2694} }
 @article{reddy_leonard_wiggins_jacob_2005, title={Internal displacement reactions in multicomponent oxides: Part II. Oxide solid solutions of wide composition range}, volume={36A}, ISSN={["1073-5623"]}, DOI={10.1007/s11661-005-0266-1}, abstractNote={As models of internal displacement reacions in oxide solid solutions, the following reactions were studied at 1273 K as a function of time: $$\begin{gathered} Fe + (Ni_x Mg_{1 - x} )O = Ni + (Fe_x Mg_{1 - x} )O \hfill \\ Fe + (Co_{0.5} Mg_{0.5} )O = Co + (Fe_{0.5} Mg_{0.5} )O \hfill \\ \end{gathered} $$ In both reactions, Ni or Co in the starting oxide is displaced by Fe and the γ-(Ni-Fe) or (Co-Fe) alloy is precipitated. In the reaction zone, composition gradients develop in both product phases, viz., the oxide and the alloy precipitate. The Ni (or Co) concentration of the alloy precipitate increases towards the reaction front. In the product oxide, the “inert” Mg diffuses toward the reaction front along with the Fe, while the Ni (or Co) diffusion is in the opposite direction, towards the Fe/boundary. The shape of the composition profiles for Mg and Fe in the product oxide suggests that cross-coefficient terms in the generalized flux equations contribute significantly to the cation flux. The parabolic rate constants of reactions involving Fe/(Ni x Mg1-x )O decrease by nearly four orders of magnitude when x decreases from 1 to 0.1.}, number={10}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Reddy, SNS and Leonard, DN and Wiggins, LB and Jacob, KT}, year={2005}, month={Oct}, pages={2695–2703} }
 @article{walker_semler_leonard_maanen_bukovnik_spontak_2002, title={ABA triblock copolymer gels modified with an A-compatible semicrystalline homopolymer}, volume={18}, ISSN={["0743-7463"]}, DOI={10.1021/la026117d}, abstractNote={In the presence of a midblock-selective solvent, ABA triblock copolymers form physical gels in which bridged and entangled B-chains establish a swollen network stabilized by A-microdomains. Here, we seek to improve the properties of an ABA gel through the addition of an A-compatible, high-molecular-weight semicrystalline homopolymer (shA). Dynamic rheology indicates that the elastic modulus increases substantially, and far beyond that achievable with an inert filler, with increasing shA content at constant solvent concentration. Transmission electron micrographs reveal the existence of nanoscale shA filaments and sheets dispersed in a micelle-stabilized gel network. The shape of the nanoscale shA objects, which are partially crystalline according to differential scanning calorimetry, and their apparent interaction with the A-rich micelles enhance network development and are responsible for the pronounced modulus increase.}, number={22}, journal={LANGMUIR}, author={Walker, TA and Semler, JJ and Leonard, DN and Maanen, GJ and Bukovnik, RR and Spontak, RJ}, year={2002}, month={Oct}, pages={8266–8270} }
 @article{leonard_russell_smith_spontak_2002, title={Multiscale dewetting of low-molecular-weight block copolymer ultrathin films}, volume={23}, ISSN={["1022-1336"]}, DOI={10.1002/1521-3927(20020201)23:3<205::AID-MARC205>3.0.CO;2-X}, abstractNote={Ultrathin films of a low-molecular-weight block copolymer spontaneously dewet after several days at ambient temperature. Film rupture produces macroscopic holes and a residual pancake brush layer ≈ 2 nm thick with intermittent mounds measuring up to 25 nm in thickness. Multiscale dewetting likewise occurs when the films are heated and returned to ambient temperature. Regardless of the surface pattern that forms during heating, submicron mounds develop on the dewetted copolymer film, and fine holes emerge along the substrate surface, after cooling.}, number={3}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Leonard, DN and Russell, PE and Smith, SD and Spontak, RJ}, year={2002}, month={Feb}, pages={205–209} }
 @article{leonard_spontak_smith_russell_2002, title={Topological coarsening of low-molecular-weight block copolymer ultrathin films by environmental AFM}, volume={43}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(02)00640-7}, abstractNote={Topological coarsening of block copolymer ultrathin films is well-understood for copolymers exhibiting intermediate or strong segregation and differing in film thickness or molecular weight at temperatures above the upper glass transition temperature (Tg), but below the order–disorder transition (TODT), of the copolymers. More recent studies suggest that the stability and topology of such films differ at temperatures above TODT. In this work, we use environmental atomic force microscopy to examine the effect of temperature on the coarsening of block copolymer ultrathin films in situ. Films measuring ca. 25 nm thick consist of a low-molecular-weight poly(styrene-b-isoprene) diblock copolymer for which the upper Tg and TODT in the bulk are about 42 and 70 °C, respectively. Time-resolved image sequences illustrating surface reorganization are obtained at temperatures below, above and near 70 °C. At temperatures very close to 70 °C, coarsening is found to slow markedly, by almost an order of magnitude relative to what is observed at higher and lower temperatures, suggesting that thermal factors may provide a means by which to inhibit the dewetting of block copolymer ultrathin films.}, number={25}, journal={POLYMER}, author={Leonard, DN and Spontak, RJ and Smith, SD and Russell, PE}, year={2002}, month={Dec}, pages={6719–6726} }
 @inbook{leonard_spontak_russell_2000, title={Environmental atomic force microscopy: Probing diblock polymer thin films and self-assembling molecules at various temperatures and pressures}, volume={165}, ISBN={0750306858}, number={2000}, booktitle={Microbeam Analysis 2000: proceedings of the Second Conference of the International Union of Microbeam Analysis Societies held in Kailua-Kona, Hawaii, 9-14 July 2000}, publisher={Bristol: Institute of Physics Publishing}, author={Leonard, D. N. and Spontak, R. J. and Russell, P. E.}, editor={Williams, D. B. and Shimizu, R.Editors}, year={2000}, pages={389–390} }
 @inbook{neves_salmon_leonard_troughton_russell_2000, title={Scratching and healing investigations on self-assembled monolayers using Atomic Force Microscopy}, volume={165}, ISBN={0750306858}, number={2000}, booktitle={Microbeam Analysis 2000: proceedings of the Second Conference of the International Union of Microbeam Analysis Societies held in Kailua-Kona, Hawaii, 9-14 July 2000}, publisher={Bristol: Institute of Physics Publishing}, author={Neves, B. R. A. and Salmon, M. E. and Leonard, D. N. and Troughton, E. B. and Russell, P. E.}, editor={Williams, D. B. and Shimizu, R.Editors}, year={2000}, pages={367–368} }
 @article{neves_leonard_salmon_russell_troughton_1999, title={Observation of topography inversion in atomic force microscopy of self-assembled monolayers}, volume={10}, ISSN={["0957-4484"]}, DOI={10.1088/0957-4484/10/4/307}, abstractNote={In this paper, we report on atomic force microscopy (AFM) investigation of a self-assembled monolayer (SAM) system - octadecylphosphonic acid (OPA) deposited on mica. With the deposition methods employed in this work, the SAM presents a partial coverage, i.e., the OPA covers only a fraction of the mica surface and, therefore, some bare mica regions are observed. Using standard intermittent contact AFM (IC-AFM) techniques (with medium to high oscillation damping), the topographic profile of this system clearly shows the flat SAM on top of the mica surface. However, when a small oscillation damping mode is employed, the topographic profile is inverted, i.e., the mica regions appear higher than the surrounding OPA layer. AFM experiments, carried out to assess the origin of this effect, yield strong evidences that it is related to the presence of a water contamination layer on the bare mica regions only. A semi-quantitative model is utilized to understand the experimental results.}, number={4}, journal={NANOTECHNOLOGY}, author={Neves, BRA and Leonard, DN and Salmon, ME and Russell, PE and Troughton, EB}, year={1999}, month={Dec}, pages={399–404} }