@article{clary_cantu_liu_evans_tracy_2024, title={Magnetic Reprogramming of Self-Assembled Hard-Magnetic Cilia}, ISSN={["2365-709X"]}, DOI={10.1002/admt.202302243}, abstractNote={Abstract Artificial magnetic cilia are hair‐like structures that can respond to magnetic fields. Using hard magnetic materials in magnetic cilia makes possible programming and reprogramming of the magnetization state and corresponding actuation behaviors. Hard‐magnetic cilia are fabricated through self‐assembly by solvent casting of a slurry of NdFeB microparticles dispersed in a solution of a thermoplastic polyurethane elastomer. These hard‐magnetic cilia are capable of attractive and repulsive responses to magnetic fields, determined by the remanent magnetization of the NdFeB microparticles. An array of cilia can be magnetically reprogrammed through immobilization in ice, applying a damped alternating magnetic field first to reduce the remanent magnetization, and then remagnetizing the cilia with a large field. This demagnetization process significantly improves the reprogrammability of the cilia array. Different responses to magnetic fields can be programmed, including spatially nonuniform behaviors. Reprogrammed hard‐magnetic cilia exhibit unique behaviors in rotating magnetic fields. After reprogramming the magnetization direction along the width of the cilia, rotation and torsion cause them to slowly coil and then quickly uncoil in a snapping behavior. Modeling the magnetic and elastic torques during actuation provides additional insights and aids the design of magnetic cilia actuators based on hard magnets.}, journal={ADVANCED MATERIALS TECHNOLOGIES}, author={Clary, Matthew R. and Cantu, Saarah N. and Liu, Jessica A. -C. and Evans, Benjamin A. and Tracy, Joseph B.}, year={2024}, month={Apr} }
 @article{ford_porcincula_telles_mancini_wang_rizvi_loeb_moran_tracy_lewis_et al._2024, title={Movement with light: Photoresponsive shape morphing of printed liquid crystal elastomers}, volume={7}, ISSN={["2590-2385"]}, DOI={10.1016/j.matt.2024.01.006}, abstractNote={Soft machines will require soft materials that exhibit a rich diversity of functionality, including shape morphing and photoresponsivity. The combination of these functionalities enables useful behaviors in soft machines that can be further developed by synthesizing materials that exhibit localized responsivity. Localized responsivity of liquid crystal elastomers (LCEs), which are soft materials that exhibit shape morphing, can be enabled by formulating composite inks for direct ink writing (DIW). Gold nanorods (AuNRs) can be added to LCEs to enable photothermal shape change upon absorption of light through a localized surface plasmon resonance. We compared LCE formulations, focusing on their amenability for printing by DIW and the photoresponsivity of AuNRs. The local responsivity of different three-dimensional architectures enabled soft machines that could oscillate, crawl, roll, transport mass, and display other unique modes of actuation and motion in response to light, making these promising functional materials for advanced applications.}, number={3}, journal={MATTER}, publisher={Elsevier BV}, author={Ford, Michael J. and Porcincula, Dominique H. and Telles, Rodrigo and Mancini, Julie A. and Wang, Yuchen and Rizvi, Mehedi H. and Loeb, Colin K. and Moran, Bryan D. and Tracy, Joseph B. and Lewis, Jennifer A. and et al.}, year={2024}, month={Mar} }
 @article{mahmood_rizvi_tracy_yingling_2023, title={Solvent Effects in Ligand Stripping Behavior of Colloidal Nanoparticles}, volume={6}, ISSN={["1936-086X"]}, url={https://doi.org/10.1021/acsnano.3c01313}, DOI={10.1021/acsnano.3c01313}, abstractNote={Inorganic colloidal nanoparticle (NP) properties can be tuned by stripping stabilizing ligands using a poor solvent. However, the mechanism behind ligand stripping is poorly understood, in part because in situ measurements of ligand stripping are challenging at the nanoscale. Here, we investigate ethanol solvent-mediated oleylamine ligand stripping from magnetite (Fe3O4) NPs in different compositions of ethanol/hexane mixtures using atomistic molecular dynamics (MD) simulations and thermogravimetric analysis (TGA). Our study elucidates a complex interplay of ethanol interactions with system components and indicates the existence of a threshold concentration of ∼34 vol % ethanol, above which ligand stripping saturates. Moreover, hydrogen bonding between ethanol and stripped ligands inhibits subsequent readsorption of the ligands on the NP surface. A proposed modification of the Langmuir isotherm explains the role of the enthalpy of mixing of the ligands and solvents on the ligand stripping mechanism. A good agreement between the MD predictions and TGA measurements of ligand stripping from Fe3O4 NPs validates the simulation observations. Our findings demonstrate that the ligand coverage of NPs can be controlled by using a poor solvent below the threshold concentration and highlight the importance of ligand-solvent interactions that modulate the properties of colloidal NPs. The study also provides an approach for a detailed in silico study of ligand stripping and exchange from colloidal NPs that are crucial for applications of NPs spanning self-assembly, optoelectronics, nanomedicine, and catalysis.}, journal={ACS NANO}, author={Mahmood, Akhlak U. and Rizvi, Mehedi H. and Tracy, Joseph B. and Yingling, Yaroslava G.}, year={2023}, month={Jun} }
 @article{song_li_chen_keshavarz_chapman_tracy_mckinley_holten-andersen_2022, title={Dynamics of dual-junction-functionality associative polymer networks with ion and nanoparticle metal-coordinate cross-link junctions}, volume={66}, ISSN={["1520-8516"]}, DOI={10.1122/8.0000410}, abstractNote={We provide a canonical introduction to dual-junction-functionality associative polymer networks, which combine high and low functionality (f) dynamic cross-link junctions to impart load-bearing, dissipation, and self-repairing ability to the network. This unique type of network configuration offers an alternative to traditional dual-junction networks consisting of covalent and reversible cross-links. The high-f junctions can provide load-bearing abilities similar to a covalent cross-link while retaining the ability to self-repair and concurrently confer stimuli-responsive properties arising from the high-f junction species. We demonstrate the mechanical properties of this design motif using metal-coordinating polymer hydrogel networks, which are dynamically cross-linked by different ratios of metal nanoparticle (high-f) and metal ion (low-f) cross-link junctions. We also demonstrate the spontaneous self-assembly of nanoparticle-cross-linked polymers into anisotropic sheets, which may be generalizable for designing dual-junction-functionality associative networks with low volume fraction percolated high-f networks.}, number={6}, journal={JOURNAL OF RHEOLOGY}, author={Song, Jake and Li, Qiaochu and Chen, Pangkuan and Keshavarz, Bavand and Chapman, Brian S. and Tracy, Joseph B. and McKinley, Gareth H. and Holten-Andersen, Niels}, year={2022}, month={Nov}, pages={1333–1345} }
 @article{rizvi_wang_schubert_crumpler_rossner_oldenburg_fery_tracy_2022, title={Magnetic Alignment for Plasmonic Control of Gold Nanorods Coated with Iron Oxide Nanoparticles}, volume={9}, ISSN={["1521-4095"]}, url={https://doi.org/10.1002/adma.202203366}, DOI={10.1002/adma.202203366}, abstractNote={Abstract}, journal={ADVANCED MATERIALS}, author={Rizvi, Mehedi H. and Wang, Ruosong and Schubert, Jonas and Crumpler, William D. and Rossner, Christian and Oldenburg, Amy L. and Fery, Andreas and Tracy, Joseph B.}, year={2022}, month={Sep} }
 @article{song_zhang_quesada_rizvi_tracy_ilavsky_narayanan_del gado_leheny_holten-andersen_et al._2022, title={Microscopic dynamics underlying the stress relaxation of arrested soft materials}, volume={119}, ISSN={["1091-6490"]}, url={https://doi.org/10.1073/pnas.2201566119}, DOI={10.1073/pnas.2201566119}, abstractNote={Arrested soft materials such as gels and glasses exhibit a slow stress relaxation with a broad distribution of relaxation times in response to linear mechanical perturbations. Although this macroscopic stress relaxation is an essential feature in the application of arrested systems as structural materials, consumer products, foods, and biological materials, the microscopic origins of this relaxation remain poorly understood. Here, we elucidate the microscopic dynamics underlying the stress relaxation of such arrested soft materials under both quiescent and mechanically perturbed conditions through X-ray photon correlation spectroscopy. By studying the dynamics of a model associative gel system that undergoes dynamical arrest in the absence of aging effects, we show that the mean stress relaxation time measured from linear rheometry is directly correlated to the quiescent superdiffusive dynamics of the microscopic clusters, which are governed by a buildup of internal stresses during arrest. We also show that perturbing the system via small mechanical deformations can result in large intermittent fluctuations in the form of avalanches, which give rise to a broad non-Gaussian spectrum of relaxation modes at short times that is observed in stress relaxation measurements. These findings suggest that the linear viscoelastic stress relaxation in arrested soft materials may be governed by nonlinear phenomena involving an interplay of internal stress relaxations and perturbation-induced intermittent avalanches.}, number={30}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Song, Jake and Zhang, Qingteng and Quesada, Felipe and Rizvi, Mehedi H. and Tracy, Joseph B. and Ilavsky, Jan and Narayanan, Suresh and Del Gado, Emanuela and Leheny, Robert L. and Holten-Andersen, Niels and et al.}, year={2022}, month={Jul} }
 @article{johnston-peck_tracy_2022, title={Size control of cobalt nanoparticles by adjusting the linear carboxylic acid ligand chain length}, volume={550}, ISSN={["1873-4766"]}, DOI={10.1016/j.jmmm.2022.169036}, abstractNote={Size control in the synthesis of Co nanoparticles (NPs) through thermolysis of Co2(CO)8 is achieved by adjusting the chain length of linear carboxylic acids used as ligands. As the chain length increases, steric effects reduce the reactivity of the carboxylic acids, thereby slowing the nucleation rate. In the subsequent growth phase, completing deposition of Co precursor onto fewer nuclei yields an increased NP size. Oxidation of Co NPs under ambient atmosphere causes formation of an antiferromagnetic CoO shell that can exchange couple to the Co core, resulting in exchange bias. The superparamagnetic blocking temperature (TB), coercivity (HC), and exchange shift (HEB) strongly depend on the size of the NP, and the most pronounced effects of exchange bias are observed for the smallest Co core size.}, journal={JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS}, author={Johnston-Peck, Aaron C. C. and Tracy, Joseph B. B.}, year={2022}, month={May} }
 @article{chandler_minevich_roark_viard_johnson_rizvi_deaton_kozlov_panigaj_tracy_et al._2021, title={Controlled Organization of Inorganic Materials Using Biological Molecules for Activating Therapeutic Functionalities}, volume={13}, ISSN={["1944-8252"]}, url={https://doi.org/10.1021/acsami.1c09230}, DOI={10.1021/acsami.1c09230}, abstractNote={Precise control over the assembly of biocompatible three-dimensional (3D) nanostructures would allow for programmed interactions within the cellular environment. Nucleic acids can be used as programmable crosslinkers to direct the assembly of quantum dots (QDs) and tuned to demonstrate different interparticle binding strategies. Morphologies of self-assembled QDs are evaluated via gel electrophoresis, transmission electron microscopy, small-angle X-ray scattering, and dissipative particle dynamics simulations, with all results being in good agreement. The controlled assembly of 3D QD organizations is demonstrated in cells via the colocalized emission of multiple assembled QDs, and their immunorecognition is assessed via enzyme-linked immunosorbent assays. RNA interference inducers are also embedded into the interparticle binding strategy to be released in human cells only upon QD assembly, which is demonstrated by specific gene silencing. The programmability and intracellular activity of QD assemblies offer a strategy for nucleic acids to imbue the structure and therapeutic function into the formation of complex networks of nanostructures, while the photoluminescent properties of the material allow for optical tracking in cells in vitro.}, number={33}, journal={ACS APPLIED MATERIALS & INTERFACES}, publisher={American Chemical Society (ACS)}, author={Chandler, Morgan and Minevich, Brian and Roark, Brandon and Viard, Mathias and Johnson, M. Brittany and Rizvi, Mehedi H. and Deaton, Thomas A. and Kozlov, Seraphim and Panigaj, Martin and Tracy, Joseph B. and et al.}, year={2021}, month={Aug}, pages={39030–39041} }
 @article{li_rizvi_lynch_tracy_ford_2021, title={Flexible Cyclic-Poly(phthalaldehyde)/Poly(epsilon-caprolactone) Blend Fibers with Fast Daylight-Triggered Transience}, volume={42}, ISSN={["1521-3927"]}, url={https://doi.org/10.1002/marc.202000657}, DOI={10.1002/marc.202000657}, abstractNote={Abstract}, number={7}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, publisher={Wiley}, author={Li, Shanshan and Rizvi, Mehedi H. and Lynch, Brian B. and Tracy, Joseph B. and Ford, Ericka}, year={2021}, month={Apr} }
 @article{yadav_rizvi_kuttich_mishra_chapman_lynch_kraus_oldenburg_tracy_2021, title={Plasmon-Coupled Gold Nanoparticles in Stretched Shape-Memory Polymers for Mechanical/Thermal Sensing}, volume={4}, ISSN={["2574-0970"]}, url={https://doi.org/10.1021/acsanm.1c00309}, DOI={10.1021/acsanm.1c00309}, abstractNote={The organization of plasmonic nanoparticles (NPs) determines the strength and polarization dependence of coupling of their surface plasmons. In this study, plasmon coupling of spherical Au NPs with...}, number={4}, journal={ACS APPLIED NANO MATERIALS}, publisher={American Chemical Society (ACS)}, author={Yadav, Prachi R. and Rizvi, Mehedi H. and Kuttich, Bjoern and Mishra, Sumeet R. and Chapman, Brian S. and Lynch, Brian B. and Kraus, Tobias and Oldenburg, Amy L. and Tracy, Joseph B.}, year={2021}, month={Apr}, pages={3911–3921} }
 @article{ha_canon bermudez_liu_oliveros mata_evans_tracy_makarov_2021, title={Reconfigurable Magnetic Origami Actuators with On-Board Sensing for Guided Assembly}, volume={33}, ISSN={["1521-4095"]}, url={https://doi.org/10.1002/adma.202008751}, DOI={10.1002/adma.202008751}, abstractNote={Abstract}, number={25}, journal={ADVANCED MATERIALS}, author={Ha, Minjeong and Canon Bermudez, Gilbert Santiago and Liu, Jessica A. -C. and Oliveros Mata, Eduardo Sergio and Evans, Benjamin A. and Tracy, Joseph B. and Makarov, Denys}, year={2021}, month={Jun} }
 @article{lynch_kelliher_anderson_japit_spencer_rizvi_sarac_augustyn_tracy_2021, title={Sulfidation and selenidation of nickel nanoparticles}, volume={3}, ISSN={["2637-9368"]}, url={https://doi.org/10.1002/cey2.83}, DOI={10.1002/cey2.83}, abstractNote={Abstract}, number={4}, journal={CARBON ENERGY}, publisher={Wiley}, author={Lynch, Brian B. and Kelliher, Andrew P. and Anderson, Bryan D. and Japit, Alexander and Spencer, Michael A. and Rizvi, Mehedi H. and Sarac, Mehmet F. and Augustyn, Veronica and Tracy, Joseph B.}, year={2021}, month={Aug}, pages={582–589} }
 @article{liu_evans_tracy_2020, title={Photothermally Reconfigurable Shape Memory Magnetic Cilia}, volume={5}, ISSN={["2365-709X"]}, url={https://doi.org/10.1002/admt.202000147}, DOI={10.1002/admt.202000147}, abstractNote={Abstract}, number={7}, journal={ADVANCED MATERIALS TECHNOLOGIES}, author={Liu, Jessica A. -C. and Evans, Benjamin A. and Tracy, Joseph B.}, year={2020}, month={Jul} }
 @article{song_rizvi_lynch_ilavsky_mankus_tracy_mckinley_holten-andersen_2020, title={Programmable Anisotropy and Percolation in Supramolecular Patchy Particle Gels}, volume={14}, url={https://doi.org/10.1021/acsnano.0c06389}, DOI={10.1021/acsnano.0c06389}, abstractNote={Patchy particle interactions are predicted to facilitate the controlled self-assembly and arrest of particles into phase-stable and morphologically tunable "equilibrium" gels, which avoids the arrested phase separation and subsequent aging that is typically observed in traditional particle gels with isotropic interactions. Despite these promising traits of patchy particle interactions, such tunable equilibrium gels have yet to be realized in the laboratory due to experimental limitations associated with synthesizing patchy particles in high yield. Here, we introduce a supramolecular metal-coordination platform consisting of metallic nanoparticles linked by telechelic polymer chains, which validates the predictions associated with patchy particle interactions and facilitates the design of equilibrium particle hydrogels through limited valency interactions. We demonstrate that the interaction valency and self-assembly of the particles can be effectively controlled by adjusting the relative concentration of polymeric linkers to nanoparticles, which enables the gelation of patchy particle hydrogels with programmable local anisotropy, morphology, and low mechanical percolation thresholds. Moreover, by crowding the local environment around the patchy particles with competing interactions, we introduce an independent method to control the self-assembly of the nanoparticles, thereby enabling the design of highly anisotropic particle hydrogels with substantially reduced percolation thresholds. We thus establish a canonical platform that facilitates multifaceted control of the self-assembly of the patchy nanoparticles en route to the design of patchy particle gels with tunable valencies, morphologies, and percolation thresholds. These advances lay important foundations for further fundamental studies of patchy particle systems and for designing tunable gel materials that address a wide range of engineering applications.}, note={PMID: 33289544}, number={12}, journal={ACS Nano}, publisher={American Chemical Society (ACS)}, author={Song, Jake and Rizvi, Mehedi H. and Lynch, Brian B. and Ilavsky, Jan and Mankus, David and Tracy, Joseph B. and McKinley, Gareth H. and Holten-Andersen, Niels}, year={2020}, month={Dec}, pages={17018–17027} }
 @article{roh_okello_golbasi_hankwitz_liu_tracy_velev_2019, title={3D-Printed Silicone Soft Architectures with Programmed Magneto-Capillary Reconfiguration}, volume={4}, ISSN={["2365-709X"]}, DOI={10.1002/admt.201800528}, abstractNote={Abstract}, number={4}, journal={ADVANCED MATERIALS TECHNOLOGIES}, publisher={Wiley}, author={Roh, Sangchul and Okello, Lilian B. and Golbasi, Nuran and Hankwitz, Jameson P. and Liu, Jessica A-C and Tracy, Joseph B. and Velev, Orlin D.}, year={2019}, month={Apr} }
 @article{chapman_mishra_tracy_2019, title={Direct electrospinning of titania nanofibers with ethanol}, volume={48}, ISSN={["1477-9234"]}, url={https://doi.org/10.1039/C9DT01872G}, DOI={10.1039/c9dt01872g}, abstractNote={TiO2 nanofibers with average diameters of ∼70 nm were prepared by direct electrospinning.}, number={34}, journal={DALTON TRANSACTIONS}, publisher={Royal Society of Chemistry (RSC)}, author={Chapman, Brian S. and Mishra, Sumeet R. and Tracy, Joseph B.}, year={2019}, month={Sep}, pages={12822–12827} }
 @article{roh_okello_golbasi_hankwitz_liu_tracy_velev_2019, title={Magnetic Actuators: 3D‐Printed Silicone Soft Architectures with Programmed Magneto‐Capillary Reconfiguration (Adv. Mater. Technol. 4/2019)}, volume={4}, ISSN={2365-709X 2365-709X}, url={http://dx.doi.org/10.1002/ADMT.201970021}, DOI={10.1002/ADMT.201970021}, abstractNote={In article number 1800528, Sangchul Roh, Orlin D. Velev, and co-workers present a new class of 3D-printed soft mesh actuators floating on water. They exhibit reversible and programmable shape reconfiguration via combined magnetic and capillary forces. The silicone meshes can carry single droplets of water and dispense them on demand.}, number={4}, journal={Advanced Materials Technologies}, publisher={Wiley}, author={Roh, Sangchul and Okello, Lilian B. and Golbasi, Nuran and Hankwitz, Jameson P. and Liu, Jessica A.‐C. and Tracy, Joseph B. and Velev, Orlin D.}, year={2019}, month={Apr}, pages={1970021} }
 @article{liu_gillen_mishra_evans_tracy_2019, title={Photothermally and magnetically controlled reconfiguration of polymer composites for soft robotics}, volume={5}, ISSN={["2375-2548"]}, url={https://doi.org/10.1126/sciadv.aaw2897}, DOI={10.1126/sciadv.aaw2897}, abstractNote={Combining photothermal heating and magnetic actuation enables the design of untethered, reconfigurable soft robots.}, number={8}, journal={SCIENCE ADVANCES}, publisher={American Association for the Advancement of Science (AAAS)}, author={Liu, Jessica A. -C. and Gillen, Jonathan H. and Mishra, Sumeet R. and Evans, Benjamin A. and Tracy, Joseph B.}, year={2019}, month={Aug} }
 @article{zhao_steves_chapman_tracy_knappenberger_2018, title={Quantification of Interface-Dependent Plasmon Quality Factors Using Single-Beam Nonlinear Optical Interferometry}, volume={90}, ISSN={["1520-6882"]}, url={https://doi.org/10.1021/acs.analchem.8b04101}, DOI={10.1021/acs.analchem.8b04101}, abstractNote={A method for quantification of plasmon mode quality factors using a novel collinear single-beam interferometric nonlinear optical (INLO) microscope is described. A collinear sequence of phase-stabilized femtosecond laser pulses generated by a series of birefringent optics is used for the INLO experiments. Our experimental designs allow for the creation of pulse replicas (800 nm carrier wave) that exhibit interpulse phase stability of 33 mrad (approximately 14 attoseonds), which can be incrementally temporally delayed from attosecond to picosecond time scales. This temporal tuning range allows for resonant electronic Fourier spectroscopy of plasmonic gold nanoparticles. The collinear geometry of the pulse pair facilitates integration into an optical microscopy platform capable of single-nanoparticle sensitivity. Analysis of the Fourier spectra in the frequency domain yields the sample plasmon resonant response and homogeneous line width; the latter provided quantification of the plasmon mode quality factor. We have applied this INLO approach to quantitatively determine the influence of encapsulation of gold nanorods with silica shells on plasmon quality factors. We have studied a series of three gold nanorod samples, distinguished by surface passivation. These include cetyltrimethylammonium bromide (CTAB)-passivated nanorods, as well as ones encapsulated by 5 and 20 nanometer-thick silica shells. The Q-factor results show a trend of increasing quality factor, increasing by 46% from 54 ± 8 to 79 ± 9, in going from CTAB- to 20 nm silica-coated AuNRs. The straightforward method of INLO enables analysis of plasmon responses to environmental influences, such as analyte binding and solvent effects, as well as quantification of structure-specific plasmon coherence dynamics.}, number={22}, journal={ANALYTICAL CHEMISTRY}, publisher={American Chemical Society (ACS)}, author={Zhao, Tian and Steves, Megan A. and Chapman, Brian S. and Tracy, Joseph B. and Knappenberger, Kenneth L., Jr.}, year={2018}, month={Nov}, pages={13702–13707} }
 @article{mishra_tracy_2018, title={Sequential Actuation of Shape-Memory Polymers through Wavelength-Selective Photothermal Heating of Gold Nanospheres and Nanorods}, volume={1}, url={https://doi.org/10.1021/acsanm.8b00394}, DOI={10.1021/acsanm.8b00394}, abstractNote={Photothermal triggering of shape-memory polymers is an appealing noncontact mode of actuation for responsive materials and soft robotics. Wavelength-selective photothermal triggering of shape recovery is reported in thermoplastic polyurethane shape-memory polymers with embedded gold (Au) nanospheres and nanorods. Light-emitting diodes with wavelengths of 530 and 860 nm matched to the surface plasmon resonances drive selective shape recovery. Wavelength-selective shape recovery enables sequential actuation, as demonstrated in a wavelength-controlled stage with optically controlled height and tilt angle using legs of shape-memory-polymer films with embedded Au nanospheres and nanorods.}, number={7}, journal={ACS Applied Nano Materials}, publisher={American Chemical Society (ACS)}, author={Mishra, Sumeet R. and Tracy, Joseph B.}, year={2018}, month={Jul}, pages={3063–3067} }
 @article{rowe_chapman_tracy_2018, title={Understanding and Controlling the Morphology of Silica Shells on Gold Nanorods}, volume={30}, ISSN={["1520-5002"]}, url={https://doi.org/10.1021/acs.chemmater.8b00794}, DOI={10.1021/acs.chemmater.8b00794}, abstractNote={Subtle variations in the conditions for addition of a tetraethyl orthosilicate (TEOS)/methanol (MeOH) solution to gold nanorods (GNRs) stabilized by cetyltrimethylammonium bromide (CTAB) allow for morphological control of silica (SiO2) shells deposited onto the GNRs. The concentration of TEOS in the TEOS/MeOH mixture determines whether the SiO2 shell uniformly coats whole GNRs or forms lobes on the ends of the GNRs. Changes in the optical absorbance spectrum of SiO2-coated GNRs (SiO2-GNRs) after purification with MeOH suggest CTAB can be removed by dissolution through the porous SiO2 shells. The size of the SiO2 lobes can be controlled, but there is a minimum lobe size, below which full encapsulation is favored. The following mechanism of lobe formation is proposed: Initially, a SiO2 shell fully encapsulates the CTAB-stabilized GNR core. Under optimized reaction conditions, determined by the MeOH concentration, the SiO2 shells can reshape into lobes, which requires sufficient solubility of SiO2 and damage...}, number={18}, journal={CHEMISTRY OF MATERIALS}, publisher={American Chemical Society (ACS)}, author={Rowe, Laurel R. and Chapman, Brian S. and Tracy, Joseph B.}, year={2018}, month={Sep}, pages={6249–6258} }
 @article{schmauch_mishra_evans_velevt_tracy_2017, title={Chained Iron Microparticles for Directionally Controlled Actuation of Soft Robots}, volume={9}, ISSN={["1944-8244"]}, url={https://doi.org/10.1021/acsami.7b01209}, DOI={10.1021/acsami.7b01209}, abstractNote={Magnetic field-directed self-assembly of magnetic particles in chains is useful for developing directionally responsive materials for applications in soft robotics. Using materials with greater complexity allows advanced functions, while still using simple device architectures. Elastomer films containing chained magnetic microparticles were prepared through solvent casting and formed into magnetically actuated lifters, accordions, valves, and pumps. Chaining both enhances actuation and imparts a directional response. Cantilevers used as lifters were able to lift up to 50 times the mass of the polymer film. We introduce the "specific torque", the torque per field per mass of magnetic particles, as a figure of merit for assessing and comparing the performance of lifters and related devices. Devices in this work generated specific torques of 68 Nm/kgT, which is significantly higher than in previously reported actuators. Applying magnetic fields to folded accordion structures caused extension and compression, depending on the accordion's orientation. In peristaltic pumps comprised of composite tubes containing embedded chains, magnetic fields caused a section of the tube to pinch closed where the field was applied. These results will facilitate both the further development of soft robots based on chained magnetic particles and efforts to engineer materials with higher specific torque.}, number={13}, journal={ACS APPLIED MATERIALS & INTERFACES}, publisher={American Chemical Society (ACS)}, author={Schmauch, Marissa M. and Mishra, Sumeet R. and Evans, Benjamin A. and Velevt, Orlin D. and Tracy, Joseph B.}, year={2017}, month={Apr}, pages={11895–11901} }
 @article{blackmon_kreda_sears_chapman_hill_tracy_ostrowski_oldenburg_2017, title={Direct monitoring of pulmonary disease treatment biomarkers using plasmonic gold nanorods with diffusion-sensitive OCT}, volume={9}, ISSN={["2040-3372"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000399429800007&KeyUID=WOS:000399429800007}, DOI={10.1039/c7nr00376e}, abstractNote={The solid concentration of pulmonary mucus (wt%) is critical to respiratory health. In patients with respiratory disease, such as Cystic Fibrosis (CF) and Chronic Obstructive Pulmonary Disorder (COPD), mucus hydration is impaired, resulting in high wt%. Mucus with high wt% is a hallmark of pulmonary disease that leads to obstructed airways, inflammation, and infection. Methods to measure mucus hydration in situ and in real-time are needed for drug development and personalized therapy. We employed plasmonic gold nanorod (GNR) biosensors that intermittently collide with macromolecules comprising the mucus mesh as they self-diffuse, such that GNR translational diffusion (DT) is sensitive to wt%. GNRs are attractive candidates for bioprobes due to their anisotropic optical scattering that makes them easily distinguishable from native tissue using polarization-sensitive OCT. Using principles of heterodyne dynamic light scattering, we developed diffusion-sensitive optical coherence tomography (DS-OCT) to spatially-resolve changing DT in real-time. DS-OCT enables, for the first time, direct monitoring of changes in nanoparticle diffusion rates that are sensitive to nanoporosity with spatial and temporal resolutions of 4.7 μm and 0.2 s. DS-OCT therefore enables us to measure spatially-resolved changes in mucus wt% over time. In this study, we demonstrate the applicability of DS-OCT on well-differentiated primary human bronchial epithelial cells during a clinical mucus-hydrating therapy, hypertonic saline treatment (HST), to reveal, for the first time, mucus mixing, cellular secretions, and mucus hydration on the micrometer scale that translate to long-term therapeutic effects.}, number={15}, journal={NANOSCALE}, publisher={Royal Society of Chemistry (RSC)}, author={Blackmon, R. L. and Kreda, S. M. and Sears, P. R. and Chapman, B. S. and Hill, D. B. and Tracy, J. B. and Ostrowski, L. E. and Oldenburg, A. L.}, year={2017}, month={Apr}, pages={4907–4917} }
 @article{niu_mcferon_godinez-salomon_chapman_damin_tracy_augustyn_rhodes_2017, title={Enhanced Electrochemical Lithium-Ion Charge Storage of Iron Oxide Nanosheets}, volume={29}, ISSN={["1520-5002"]}, url={https://doi.org/10.1021/acs.chemmater.7b02315}, DOI={10.1021/acs.chemmater.7b02315}, abstractNote={Iron oxides are appealing cathode materials for low-cost electrochemical energy storage, but iron oxide nanoparticles (NPs) exhibit very low capacities, particularly at fast charging and discharging times, which are increasingly important for numerous applications. We report that synthesis and stabilization of iron oxide in nanosheets results in significantly improved lithium-ion charge storage capacities compared to those of iron oxide NPs at both slow and fast charging/discharging times. The iron oxide nanosheets have lateral dimensions of ∼50 nm and thicknesses of ∼1 nm and are composed of smaller crystallites. The structure of the nanosheets is consistent with maghemite, γ-Fe2O3, which contains cation defects. The γ-Fe2O3 phase is not typically observed within a nanosheet form, and γ-Fe2O3 nanosheets transform to NPs at a relatively low temperature of 200 °C. The transformation of γ-Fe2O3 from a nanosheet to an NP occurs in conjunction with removal of structural H2O. The γ-Fe2O3 nanosheets exhibited l...}, number={18}, journal={CHEMISTRY OF MATERIALS}, publisher={American Chemical Society (ACS)}, author={Niu, Sibo and McFeron, Ryan and Godinez-Salomon, Fernando and Chapman, Brian S. and Damin, Craig A. and Tracy, Joseph B. and Augustyn, Veronica and Rhodes, Christopher P.}, year={2017}, month={Sep}, pages={7794–7807} }
 @article{chapman_wu_li_holten-andersen_tracy_2017, title={Heteroaggregation Approach for Depositing Magnetite Nanoparticles onto Silica-Overcoated Gold Nanorods}, volume={29}, ISSN={["1520-5002"]}, url={https://doi.org/10.1021/acs.chemmater.7b03481}, DOI={10.1021/acs.chemmater.7b03481}, abstractNote={Hydrophobic, oleylamine-stabilized magnetite nanoparticles (Fe3O4 NPs) dispersed in hexanes can assemble into dense coatings on the surface of silica-overcoated gold nanorods (SiO2-GNRs) dispersed in ethanol by mixing. In this nonaqueous heteroaggregation process, Fe3O4 NPs are destabilized when ethanol is added, resulting in core/satellite Fe3O4-SiO2-GNRs within a few minutes. The composition of the solvent mixture allows tuning of the polarity and driving forces toward aggregation. At the optimal 2:1 volume ratio of hexanes:ethanol, heteroaggregation to form Fe3O4-SiO2-GNRs occurs quickly, while avoiding homoaggregation of Fe3O4 NPs or SiO2-GNRs. Fe3O4-SiO2-GNRs retain the longitudinal surface plasmon resonance of the gold nanorod cores and are magnetically responsive and separable. The Fe3O4 NPs remain bound on the surface of the Fe3O4-SiO2-GNRs during multiple cycles of magnetic extraction and redispersion. Oleylamine ligands on the Fe3O4 NPs render the Fe3O4-SiO2-GNRs dispersible in nonpolar solvents...}, number={24}, journal={CHEMISTRY OF MATERIALS}, publisher={American Chemical Society (ACS)}, author={Chapman, Brian S. and Wu, Wei-Chen and Li, Qiaochu and Holten-Andersen, Niels and Tracy, Joseph B.}, year={2017}, month={Dec}, pages={10362–10368} }
 @article{ashley_vakil_lynch_dyer_tracy_owens_strouse_2017, title={Microwave Enhancement of Autocatalytic Growth of Nanometals}, volume={11}, ISSN={["1936-086X"]}, url={https://doi.org/10.1021/acsnano.7b04040}, DOI={10.1021/acsnano.7b04040}, abstractNote={The desire for designing efficient synthetic methods that lead to industrially important nanomaterials has led a desire to more fully understand the mechanism of growth and how modern synthetic techniques can be employed. Microwave (MW) synthesis is one such technique that has attracted attention as a green, sustainable method. The reports of enhancement of formation rates and improved quality for MW driven reactions are intriguing, but the lack of understanding of the reaction mechanism and how coupling to the MW field leads to these observations is concerning. In this manuscript, the growth of a metal nanoparticles (NPs) in a microwave cavity is spectroscopically analyzed and compared with the classical autocatalytic method of NP growth to elucidate the underpinnings for the observed enhanced growth behavior for metal NPs prepared in a MW field. The study illustrates that microwave synthesis of nickel and gold NPs below saturation conditions follows the Finke-Watzky mechanism of nucleation and growth. The enhancement of the reaction arises from the size-dependent increase in MW absorption cross section for the metal NPs. For Ni, the presence of oxides is considered via theoretical computations and compared to dielectric measurements of isolated nickel NPs. The study definitively shows that MW growth can be modeled by an autocatalytic mechanism that directly leads to the observed enhanced rates and improved quality widely reported in the nanomaterial community when MW irradiation is employed.}, number={10}, journal={ACS NANO}, publisher={American Chemical Society (ACS)}, author={Ashley, Bridgett and Vakil, Parth N. and Lynch, Brian B. and Dyer, Christopher M. and Tracy, Joseph B. and Owens, Jeffery and Strouse, Geoffrey F.}, year={2017}, month={Oct}, pages={9957–9967} }
 @article{maity_wu_tracy_clarke_bochinski_2017, title={Nanoscale steady-state temperature gradients within polymer nanocomposites undergoing continuous-wave photothermal heating from gold nanorods}, volume={9}, ISSN={["2040-3372"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000407812000028&KeyUID=WOS:000407812000028}, DOI={10.1039/C7NR04613H}, abstractNote={Anisotropically-shaped metal nanoparticles act as nanoscale heaters via excitation of a localized surface plasmon resonance, utilizing a photothermal effect which converts the optical energy into local heat.}, number={32}, journal={NANOSCALE}, publisher={Royal Society of Chemistry (RSC)}, author={Maity, Somsubhra and Wu, Wei-Chen and Tracy, Joseph B. and Clarke, Laura I. and Bochinski, Jason R.}, year={2017}, month={Aug}, pages={11605–11618} }
 @article{marusak_johnston-peck_wu_anderson_tracy_2017, title={Size and Composition Control of CoNi Nanoparticles and Their Conversion into Phosphides}, volume={29}, ISSN={["1520-5002"]}, url={https://doi.org/10.1021/acs.chemmater.6b04335}, DOI={10.1021/acs.chemmater.6b04335}, abstractNote={The synthesis of binary rather than unary metal nanoparticles (NPs) introduces challenges in controlling the chemistry and opportunities to tune the properties of the products. Ligand-stabilized CoNi NPs were synthesized by heating mixtures of Ni(acac)2 and Co(acac)2 (acac = acetylacetonate), oleylamine, trioctylphosphine, and trioctylphosphine oxide to 240 °C. Varying the amounts of the Co and Ni precursors allows for control over the NP size, giving diameters of 6–18 nm and compositions (XCo) of ≤0.7. The products are enriched with Ni, in comparison with the Co:Ni ratio of the precursors. Co and Ni are both dispersed throughout the NPs, while the shells are enriched with Co. The magnetic properties of CoNi NPs are between those of magnetically soft Ni and magnetically harder Co, with additional effects caused by oxidation under ambient atmosphere, which gives rise to exchange bias. When the reaction mixture for synthesizing CoNi NPs is heated to 300 °C, trioctylphosphine decomposes, and conversion into ...}, number={7}, journal={CHEMISTRY OF MATERIALS}, publisher={American Chemical Society (ACS)}, author={Marusak, Katherine E. and Johnston-Peck, Aaron C. and Wu, Wei-Chen and Anderson, Bryan D. and Tracy, Joseph B.}, year={2017}, month={Apr}, pages={2739–2747} }
 @article{lynch_anderson_kennedy_tracy_2017, title={Synthesis and chemical transformation of Ni nanoparticles embedded in silica}, url={https://doi.org/10.1039/C7NR06379B}, DOI={10.1039/C7NR06379B}, abstractNote={Overcoating Ni nanoparticles with SiO2 etches, oxidizes, and embeds them in SiO2, which provides stability during oxidation and reduction.}, journal={Nanoscale}, publisher={Royal Society of Chemistry (RSC)}, author={Lynch, Brian B. and Anderson, Bryan D. and Kennedy, W. Joshua and Tracy, Joseph B.}, year={2017} }
 @article{blackmon_kreda_sears_ostrowski_hill_chapman_tracy_oldenburg_2016, title={Diffusion-sensitive optical coherence tomography for real-time monitoring of mucus thinning treatments}, volume={9697}, ISSN={["0277-786X"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000378122900061&KeyUID=WOS:000378122900061}, DOI={10.1117/12.2208805}, abstractNote={Mucus hydration (wt%) has become an increasingly useful metric in real-time assessment of respiratory health in diseases like cystic fibrosis and COPD, with higher wt% indicative of diseased states. However, available in vivo rheological techniques are lacking. Gold nanorods (GNRs) are attractive biological probes whose diffusion through tissue is sensitive to the correlation length of comprising biopolymers. Through employment of dynamic light scattering theory on OCT signals from GNRs, we find that weakly-constrained GNR diffusion predictably decreases with increasing wt% (more disease-like) mucus. Previously, we determined this method is robust against mucus transport on human bronchial epithelial (hBE) air-liquid interface cultures (R2=0.976). Here we introduce diffusion-sensitive OCT (DS-OCT), where we collect M-mode image ensembles, from which we derive depth- and temporally-resolved GNR diffusion rates. DS-OCT allows for real-time monitoring of changing GNR diffusion as a result of topically applied mucus-thinning agents, enabling monitoring of the dynamics of mucus hydration never before seen. Cultured human airway epithelial cells (Calu-3 cell) with a layer of endogenous mucus were doped with topically deposited GNRs (80x22nm), and subsequently treated with hypertonic saline (HS) or isotonic saline (IS). DS-OCT provided imaging of the mucus thinning response up to a depth of 600μm with 4.65μm resolution, over a total of 8 minutes in increments of ≥3 seconds. For both IS and HS conditions, DS-OCT captured changes in the pattern of mucus hydration over time. DS-OCT opens a new window into understanding mechanisms of mucus thinning during treatment, enabling real-time efficacy feedback needed to optimize and tailor treatments for individual patients.}, journal={OPTICAL COHERENCE TOMOGRAPHY AND COHERENCE DOMAIN OPTICAL METHODS IN BIOMEDICINE XX}, author={Blackmon, Richard L. and Kreda, Silvia M. and Sears, Patrick R. and Ostrowski, Lawrence E. and Hill, David B. and Chapman, Brian S. and Tracy, Joseph B. and Oldenburg, Amy L.}, year={2016} }
 @article{blackmon_sandhu_chapman_casbas-hernandez_tracy_troester_oldenburg_2016, title={Imaging Extracellular Matrix Remodeling In Vitro by Diffusion-Sensitive Optical Coherence Tomography}, volume={110}, ISSN={["1542-0086"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000374859600019&KeyUID=WOS:000374859600019}, DOI={10.1016/j.bpj.2016.03.014}, abstractNote={The mammary gland extracellular matrix (ECM) is comprised of biopolymers, primarily collagen I, that are created and maintained by stromal fibroblasts. ECM remodeling by fibroblasts results in changes in ECM fiber spacing (pores) that have been shown to play a critical role in the aggressiveness of breast cancer. However, minimally invasive methods to measure the spatial distribution of ECM pore areas within tissues and in vitro 3D culture models are currently lacking. We introduce diffusion-sensitive optical coherence tomography (DS-OCT) to image the nanoscale porosity of ECM by sensing weakly constrained diffusion of gold nanorods (GNRs). DS-OCT combines the principles of low-coherence interferometry and heterodyne dynamic light scattering. By collecting co- and cross-polarized light backscattered from GNRs within tissue culture, the ensemble-averaged translational self-diffusion rate, DT, of GNRs is resolved within ∼3 coherence volumes (10 × 5 μm, x × z). As GNRs are slowed by intermittent collisions with ECM fibers, DT is sensitive to ECM porosity on the size scale of their hydrodynamic diameter (∼46 nm). Here, we validate the utility of DS-OCT using pure collagen I gels and 3D mammary fibroblast cultures seeded in collagen/Matrigel, and associate differences in artificial ECM pore areas with gel concentration and cell seed density. Across all samples, DT was highly correlated with pore area obtained by scanning electron microscopy (R(2) = 0.968). We also demonstrate that DS-OCT can accurately map the spatial heterogeneity of layered samples. Importantly, DS-OCT of 3D mammary fibroblast cultures revealed the impact of fibroblast remodeling, where the spatial heterogeneity of matrix porosity was found to increase with cell density. This provides an unprecedented view into nanoscale changes in artificial ECM porosity over effective pore diameters ranging from ∼43 to 360 nm using a micron-scale optical imaging technique. In combination with the topical deposition of GNRs, the minimally invasive nature of DS-OCT makes this a promising technology for studying tissue remodeling processes.}, number={8}, journal={BIOPHYSICAL JOURNAL}, author={Blackmon, Richard L. and Sandhu, Rupninder and Chapman, Brian S. and Casbas-Hernandez, Patricia and Tracy, Joseph B. and Troester, Melissa A. and Oldenburg, Amy L.}, year={2016}, month={Apr}, pages={1858–1868} }
 @article{mishra_dickey_velev_tracy_2016, title={Selective and directional actuation of elastomer films using chained magnetic nanoparticles}, volume={8}, ISSN={["2040-3372"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000368040200008&KeyUID=WOS:000368040200008}, DOI={10.1039/c5nr07410j}, abstractNote={One-dimensional arrangement of magnetic nanoparticles in chains imparts anisotropy to their magnetic response, which is used for mechanical 3D actuation.}, number={3}, journal={NANOSCALE}, publisher={Royal Society of Chemistry (RSC)}, author={Mishra, Sumeet R. and Dickey, Michael D. and Velev, Orlin D. and Tracy, Joseph B.}, year={2016}, pages={1309–1313} }
 @article{anderson_wu_tracy_2016, title={Silica Overcoating of CdSe/CdS Core/Shell Quantum Dot Nanorods with Controlled Morphologies}, volume={28}, ISSN={["1520-5002"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000380576700010&KeyUID=WOS:000380576700010}, DOI={10.1021/acs.chemmater.6b01225}, abstractNote={CdSe/CdS core/shell quantum dot nanorods (QDNRs) exhibit anisotropic optical properties. Overcoating QDNRs with silica (SiO2) shells is desirable for protecting the surface of the inorganic core, imparting dispersibility in water, and allowing functionalization with silanes. While several methods have been developed for encapsulating spherical CdSe-based quantum dots in SiO2, extension of these approaches to QDNRs has been limited. Here, we report a reverse microemulsion approach for controlled deposition of SiO2 overcoatings with thicknesses of 2–12 nm onto CdSe/CdS QDNRs with aspect ratios of up to 19. Addition of poly(ethylene glycol) silane during SiO2 deposition terminates the reaction and allows facile control over the shell thickness, especially for thinner shells. By independently controlling the amounts of tetraethyl orthosilicate, ammonium hydroxide (NH4OH), and water, morphological control is achieved, giving uniform SiO2 shells or heterogenenous deposition onto the ends of QDNRs as lobed struc...}, number={14}, journal={CHEMISTRY OF MATERIALS}, author={Anderson, Bryan D. and Wu, Wei-Chen and Tracy, Joseph B.}, year={2016}, month={Jul}, pages={4945–4952} }
 @article{pacardo_neupane_rikard_lu_mo_mishra_tracy_wang_ligler_gu_2015, title={A dual wavelength-activatable gold nanorod complex for synergistic cancer treatment}, volume={7}, ISSN={["2040-3372"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000357805700034&KeyUID=WOS:000357805700034}, DOI={10.1039/c5nr01568e}, abstractNote={A multifunctional gold nanorod complex was formulated for synergistic anticancer treatment upon ultraviolet (UV) and infrared (IR) light dual irradiations.}, number={28}, journal={NANOSCALE}, author={Pacardo, Dennis B. and Neupane, Bhanu and Rikard, S. Michaela and Lu, Yue and Mo, Ran and Mishra, Sumeet R. and Tracy, Joseph B. and Wang, Gufeng and Ligler, Frances S. and Gu, Zhen}, year={2015}, pages={12096–12103} }
 @article{wu_tracy_2015, title={Large-Scale Silica Overcoating of Gold Nanorods with Tunable Shell Thicknesses}, volume={27}, ISSN={["1520-5002"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000353865800021&KeyUID=WOS:000353865800021}, DOI={10.1021/cm504764v}, abstractNote={Gold nanorods (GNRs) overcoated with SiO2 are of interest for enhancing the shape stability of GNRs during photothermal heating, for further functionalization with silanes, and for biomedical applications. While methods have recently been developed for synthesizing GNRs on a large scale, SiO2 overcoating of GNRs is still conducted on a small reaction scale. Here, we report a method for large-scale synthesis of SiO2-overcoated GNRs (SiO2-GNRs), which gives ∼190 mg of SiO2-GNRs. SiO2 is deposited onto and encapsulates the cetyltrimethylammonium bromide (CTAB) coatings that stabilize GNRs by adding tetraethoxysilane (TEOS) via syringe pump. Control over the CTAB concentration is critically important for obtaining uniform overcoatings. Optical absorbance spectra of SiO2-GNRs closely resemble those of uncoated GNRs, which indicates overcoating of single rather than multiple GNRs and confirms that they remain well dispersed. By adjusting the reaction conditions, shells as thick as ∼20 nm can be obtained. For thin shells (<10 nm), addition of poly(ethylene glycol) silane (PEG-silane) at different times during the overcoating reaction allows facile control over the shell thickness, giving shells as thin as ∼2 nm. The bulky PEG chain terminates further cross-linking and deposition of SiO2.}, number={8}, journal={CHEMISTRY OF MATERIALS}, author={Wu, Wei-Chen and Tracy, Joseph B.}, year={2015}, month={Apr}, pages={2888–2894} }
 @article{gonzalez_wu_tracy_martin_2015, title={Photochemical synthesis of size-tailored hexagonal ZnS quantum dots}, volume={51}, ISSN={["1364-548X"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000349324200014&KeyUID=WOS:000349324200014}, DOI={10.1039/c4cc09222h}, abstractNote={Photochemically generated ketyl radicals were employed for the synthesis of hexagonal ZnS quantum dots at room temperature.}, number={15}, journal={CHEMICAL COMMUNICATIONS}, author={Gonzalez, Carlos M. and Wu, Wei-Chen and Tracy, Joseph B. and Martin, Benjamin}, year={2015}, pages={3087–3090} }
 @article{padbury_halbur_krommenhoek_tracy_jur_2015, title={Thermal Stability of Gold Nanoparticles Embedded within Metal Oxide Frameworks Fabricated by Hybrid Modifications onto Sacrificial Textile Templates}, volume={31}, ISSN={0743-7463 1520-5827}, url={http://dx.doi.org/10.1021/LA504094G}, DOI={10.1021/la504094g}, abstractNote={The stability and spatial separation of nanoparticles (NP's) is essential for employing their advantageous nanoscale properties. This work demonstrates the entrapment of gold NP's embedded in a porous inorganic matrix. Initially, gold NP's are decorated on fibrous nylon-6, which is used as an inexpensive sacrificial template. This is followed by inorganic modification using a novel single exposure cycle vapor phase technique resulting in distributed NP's embedded within a hybrid organic-inorganic matrix. The processing is extended to the synthesis of porous nanoflakes after calcination of the modified nylon-6 yielding a porous metal oxide framework surrounding the disconnected NP's with a surface area of 250 m(2)/g. A unique feature of this work is the use of a transmission electron microscope (TEM) equipped with an in situ annealing sample holder. The apparatus affords the opportunity to explore the underlying nanoscopic stability of NP's embedded in these frameworks in a single step. TEM analysis indicates thermal stability up to 670 °C and agglomeration characteristics thereafter. The vapor phase processes developed in this work will facilitate new complex NP/oxide materials useful for catalytic platforms.}, number={3}, journal={Langmuir}, publisher={American Chemical Society (ACS)}, author={Padbury, Richard P. and Halbur, Jonathan C. and Krommenhoek, Peter J. and Tracy, Joseph B. and Jur, Jesse S.}, year={2015}, month={Jan}, pages={1135–1141} }
 @article{kodumagulla_varanasi_pearce_wu_hensley_tracy_mcknight_melechko_2014, title={Aerosynthesis: Growth of Vertically-aligned Carbon Nanofibres with Air DC Plasma}, volume={4}, ISSN={["1847-9804"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000333365200001&KeyUID=WOS:000333365200001}, DOI={10.5772/58449}, abstractNote={ Vertically-aligned carbon nanofibres (VACNFs) have been synthesized in a mixture of acetone and air using catalytic DC plasma-enhanced chemical vapour deposition. Typically, ammonia or hydrogen is used as an etchant gas in the mixture to remove carbon that otherwise passivates the catalyst surface and impedes growth. Our demonstration of the use of air as the etchant gas opens up the possibility that ion etching could be sufficient to maintain the catalytic activity state during synthesis. It also demonstrates a path toward growing VACNFs in the open atmosphere. }, journal={NANOMATERIALS AND NANOTECHNOLOGY}, author={Kodumagulla, A. and Varanasi, V. and Pearce, R. C. and Wu, W. C. and Hensley, D. K. and Tracy, J. B. and McKnight, T. E. and Melechko, A. V.}, year={2014}, month={Mar} }
 @article{sarac_wu_tracy_2014, title={Control of Branching in Ni3C1-x Nanoparticles and Their Conversion into Ni12P5 Nanoparticles}, volume={26}, ISSN={["1520-5002"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000336637000006&KeyUID=WOS:000336637000006}, DOI={10.1021/cm4034353}, abstractNote={Dendritic Ni3C1–x nanoparticles (NPs) with controlled branching have been synthesized through the thermolysis (230 °C) of nickel acetylacetonate using oleylamine as a reducing agent and 1-octadecene (ODE) as the solvent. Addition of trioctylphosphine (TOP) as a ligand inhibits formation of dendritic shapes and prevents incorporation of C, resulting in spherical Ni NPs. In comparison, when using octadecane (ODA) or trioctylphosphine oxide (TOPO) as the solvent, Ni NPs are obtained at 230 °C that have fewer, larger branches than when using ODE. Higher temperatures are required for incorporation of C from ODA or TOPO into Ni NPs, resulting in Ni3C1–x NPs. Therefore, the allyl group in ODE facilitates formation of Ni3C1–x NPs at lower temperatures. Conversion of dendritic Ni3C1–x NPs into Ni12P5 NPs after adding TOP and heating to 300 °C results in the formation of multiple voids in the branches, rather than yolk-in-shell structures or unfilled single voids observed for spherical NPs.}, number={10}, journal={CHEMISTRY OF MATERIALS}, author={Sarac, Mehmet F. and Wu, Wei-Chen and Tracy, Joseph B.}, year={2014}, month={May}, pages={3057–3064} }
 @article{wu_tracy_2014, title={Large-scale silica overcoating of gold nanorods and their thermal stability}, volume={248}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000349165100015&KeyUID=WOS:000349165100015}, journal={Abstracts of Papers of the American Chemical Society}, author={Wu, Wei-Chen and Tracy, Joseph B.}, year={2014} }
 @article{wu_tracy_2014, title={Large-scale silica overcoating of gold nanorods with tunable shell thicknesses}, volume={248}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000349165104127&KeyUID=WOS:000349165104127}, journal={Abstracts of Papers of the American Chemical Society}, author={Wu, Wei-Chen and Tracy, Joseph B.}, year={2014} }
 @misc{anderson_tracy_2014, title={Nanoparticle conversion chemistry: Kirkendall effect, galvanic exchange, and anion exchange}, volume={6}, ISSN={["2040-3372"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000344997500001&KeyUID=WOS:000344997500001}, DOI={10.1039/c4nr02025a}, abstractNote={Review article discussing recent advances in conversion chemistry of nanoparticles through the Kirkendall effect, galvanic exchange, and anion exchange.}, number={21}, journal={NANOSCALE}, author={Anderson, Bryan D. and Tracy, Joseph B.}, year={2014}, pages={12195–12216} }
 @article{chhetri_blackmon_wu_hill_button_casbas-hernandez_troester_tracy_oldenburg_2014, title={Probing biological nanotopology via diffusion of weakly constrained plasmonic nanorods with optical coherence tomography}, volume={111}, ISSN={["0027-8424"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000342922000006&KeyUID=WOS:000342922000006}, DOI={10.1073/pnas.1409321111}, abstractNote={Significance}, number={41}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Chhetri, Raghav K. and Blackmon, Richard L. and Wu, Wei-Chen and Hill, David B. and Button, Brian and Casbas-Hernandez, Patricia and Troester, Melissa A. and Tracy, Joseph B. and Oldenburg, Amy L.}, year={2014}, month={Oct}, pages={E4289–E4297} }
 @article{maity_wu_xu_tracy_gundogdu_bochinski_clarke_2014, title={Spatial temperature mapping within polymer nanocomposites undergoing ultrafast photothermal heating via gold nanorods}, volume={6}, ISSN={["2040-3372"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000345458200080&KeyUID=WOS:000345458200080}, DOI={10.1039/c4nr05179c}, abstractNote={Polarized fluorescence temperature measurements combined with direct detection of nanorod rotation within the polymer melt regions reveal the steady-state temperature gradient on the nanoscale.}, number={24}, journal={NANOSCALE}, author={Maity, Somsubhra and Wu, Wei-Chen and Xu, Chao and Tracy, Joseph B. and Gundogdu, Kenan and Bochinski, Jason R. and Clarke, Laura I.}, year={2014}, pages={15236–15247} }
 @article{wu_tracy_2014, title={Thermal stability of silica-coated and uncoated gold nanorods in different environments}, volume={248}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000349167401528&KeyUID=WOS:000349167401528}, journal={Abstracts of Papers of the American Chemical Society}, author={Wu, Wei-Chen and Tracy, Joseph B.}, year={2014} }
 @article{sarac_anderson_pearce_railsback_oni_white_hensley_lebeau_melechko_tracy_2013, title={Airbrushed Nickel Nanoparticles for Large-Area Growth of Vertically Aligned Carbon Nanofibers on Metal (Al, Cu, Ti) Surfaces}, volume={5}, ISSN={["1944-8244"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000330016500022&KeyUID=WOS:000330016500022}, DOI={10.1021/am401889t}, abstractNote={Vertically aligned carbon nanofibers (VACNFs) were grown by plasma-enhanced chemical vapor deposition (PECVD) using Ni nanoparticle (NP) catalysts that were deposited by airbrushing onto Si, Al, Cu, and Ti substrates. Airbrushing is a simple method for depositing catalyst NPs over large areas that is compatible with roll-to-roll processing. The distribution and morphology of VACNFs are affected by the airbrushing parameters and the composition of the metal foil. Highly concentrated Ni NPs in heptane give more uniform distributions than pentane and hexanes, resulting in more uniform coverage of VACNFs. For VACNF growth on metal foils, Si micropowder was added as a precursor for Si-enriched coatings formed in situ on the VACNFs that impart mechanical rigidity. Interactions between the catalyst NPs and the metal substrates impart control over the VACNF morphology. Growth of carbon nanostructures on Cu is particularly noteworthy because the miscibility of Ni with Cu poses challenges for VACNF growth, and carbon nanostructures anchored to Cu substrates are desired as anode materials for Li-ion batteries and for thermal interface materials.}, number={18}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Sarac, Mehmet F. and Anderson, Bryan D. and Pearce, Ryan C. and Railsback, Justin G. and Oni, Adedapo A. and White, Ryan M. and Hensley, Dale K. and LeBeau, James M. and Melechko, Anatoli V. and Tracy, Joseph B.}, year={2013}, month={Sep}, pages={8955–8960} }
 @article{sarac_pearce_anderson_railsback_hensley_mcknight_tracy_melechko_2013, title={Airbrushed nickel nanoparticles for large-area growth of vertically aligned carbon nanofibers on metal surfaces and their transfer into polydimethylsiloxane (PDMS) films for impalefection}, volume={245}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000324303601022&KeyUID=WOS:000324303601022}, journal={Abstracts of Papers of the American Chemical Society}, author={Sarac, Mehmet F. and Pearce, Ryan C. and Anderson, Bryan D. and Railsback, Justin G. and Hensley, Dale K. and McKnight, Timothy E. and Tracy, Joseph B. and Melechko, Anatoli V.}, year={2013} }
 @article{maity_kozek_wu_tracy_bochinski_clarke_2013, title={Anisotropic Thermal Processing of Polymer Nanocomposites via the Photothermal Effect of Gold Nanorods}, volume={30}, ISSN={["1521-4117"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000315360400010&KeyUID=WOS:000315360400010}, DOI={10.1002/ppsc.201200084}, abstractNote={By embedding metal nanoparticles within polymeric materials, selective thermal polymer processing can be accomplished via irradiation with light resonant with the nanoparticle surface plasmon resonance due to the photothermal effect of the nanoparticles which efficiently transforms light into heat. The wavelength and polarization sensitivity of photothermal heating from embedded gold nanorods is used to selectively process a collection of polymeric nanofibers, completely melting those fibers lying along a chosen direction while leaving the remaining material largely unheated and unaffected. Fluorescence‐based temperature and viscosity sensing was employed to confirm the presence of heating and melting in selected fibers and its absence in counter‐aligned fibers. Such tunable specificity in processing a subset of a sample, while the remainder is unchanged, cannot easily be achieved through conventional heating techniques.}, number={2}, journal={PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION}, author={Maity, Somsubhra and Kozek, Krystian A. and Wu, Wei-Chen and Tracy, Joseph B. and Bochinski, Jason R. and Clarke, Laura I.}, year={2013}, month={Feb}, pages={193–202} }
 @article{krommenhoek_wang_hentz_johnston-peck_kozek_kalyuzhny_tracy_2013, title={Bulky adamantanethiolate and cyclohexanethiolate ligands favor smaller gold nanoparticles with altered discrete sizes}, volume={245}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000324303601027&KeyUID=WOS:000324303601027}, journal={Abstracts of Papers of the American Chemical Society}, author={Krommenhoek, Peter J. and Wang, Junwei and Hentz, Nathaniel and Johnston-Peck, Aaron C. and Kozek, Krystian A. and Kalyuzhny, Gregory and Tracy, Joseph B.}, year={2013} }
 @article{oni_white_sarac_anderson_pearce_railsback_hensley_melechko_tracy_lebeau_2013, title={Chemical Analysis of Airbrushed Nickel Nanoparticles for Large-Area Growth of Vertically Aligned Carbon Nanofibers on Metal Surfaces}, volume={19}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927613009859}, DOI={10.1017/S1431927613009859}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.}, number={S2}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Oni, A. and White, R. and Sarac, M. and Anderson, B. and Pearce, R. and Railsback, J. and Hensley, D. and Melechko, A. and Tracy, J. and LeBeau, J.}, year={2013}, month={Aug}, pages={1572–1573} }
 @article{johnston-peck_cullen_tracy_2013, title={Composition-Mediated Order-Disorder Transformation in FePt Nanoparticles}, volume={30}, ISSN={["1521-4117"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000327250400008&KeyUID=WOS:000327250400008}, DOI={10.1002/ppsc.201300028}, abstractNote={Thumbnail image of graphical abstract Heat-treated alloy FePt nanoparticles transform into L10 FePt and mixed L10/L12 FePt3 intermetallic phases. Enrichment in Pt in some nanoparticles, rather than intrinsic thermodynamic effects, drives phase segregation. FePt nanoparticles of uniform, equimolar composition are expected to transform into phase-pure, highly ordered L10 FePt nanoparticles.}, number={8}, journal={PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION}, author={Johnston-Peck, Aaron C. and Cullen, David A. and Tracy, Joseph B.}, year={2013}, month={Aug}, pages={678–682} }
 @article{sarac_wu_tracy_2013, title={Control of branching in dendritic Ni3C1-x nanoparticles and their conversion into phosphides}, volume={246}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000329618404556&KeyUID=WOS:000329618404556}, journal={Abstracts of Papers of the American Chemical Society}, author={Sarac, Mehmet F. and Wu, Wei-Chen and Tracy, Joseph B.}, year={2013} }
 @article{kozek_kozek_wu_mishra_tracy_2013, title={Large-Scale Synthesis of Gold Nanorods through Continuous Secondary Growth}, volume={25}, ISSN={["1520-5002"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000327752500010&KeyUID=WOS:000327752500010}, DOI={10.1021/cm402277y}, abstractNote={Gold nanorods (GNRs) exhibit a tunable longitudinal surface plasmon resonance (LSPR) that depends on the GNR aspect ratio (AR). Independently controlling the AR and size of GNRs remains challenging but is important because the scattering intensity strongly depends on the GNR size. Here, we report a secondary (seeded) growth procedure, wherein continuous addition of ascorbic acid (AA) to a stirring solution of GNRs, stabilized by cetyltrimethylammonium bromide (CTAB) and synthesized by a common GNR growth procedure, deposits the remaining (~70%) of the Au precursor onto the GNRs. The growth phase of GNR synthesis is often performed without stirring, since stirring has been believed to reduce the yield of rod-shaped nanoparticles, but we report that stirring coupled with continuous addition of AA during secondary growth allows improved control over the AR and size of GNRs. After a common primary GNR growth procedure, the LSPR of GNRs is ~820 nm, which can be tuned between ~700-880 nm during secondary growth by adjusting the rate of AA addition or adding benzyldimethylhexadecylammonium chloride hydrate (BDAC). This approach for secondary growth can also be used with primary GNRs of different ARs to achieve different LSPRs and can likely be extended to nanoparticles of different shapes and other metals.}, number={22}, journal={CHEMISTRY OF MATERIALS}, author={Kozek, Krystian A. and Kozek, Klaudia M. and Wu, Wei-Chen and Mishra, Sumeet R. and Tracy, Joseph B.}, year={2013}, month={Nov}, pages={4537–4544} }
 @article{krommenhoek_tracy_2013, title={Magnetic Field-Directed Self-Assembly of Magnetic Nanoparticle Chains in Bulk Polymers}, volume={30}, ISSN={["1521-4117"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000327250600004&KeyUID=WOS:000327250600004}, DOI={10.1002/ppsc.201300101}, abstractNote={Peter J. Krommenhoek and Joseph B. Tracy * IO N Self-assembly is the thermodynamically guided organization of disordered systems into more highly ordered structures. The process of life exemplifi es the power and diversity of selfassembly, and understanding and controlling self-assembly is crucial for engineering advanced materials from molecular and nanoscale precursors. Nature has preceded researchers’ efforts in magnetic fi eld-directed self-assembly (MFDSA) in magnetotactic bacteria, which navigate in the earth’s magnetic fi eld using magnetically coupled chains of iron oxide nanoparticles (NPs). [ 1 ]}, number={9}, journal={PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION}, author={Krommenhoek, Peter J. and Tracy, Joseph B.}, year={2013}, month={Sep}, pages={759–763} }
 @article{krommenhoek_spontak_tracy_2013, title={Magnetic field-directed self-assembly of magnetic nanoparticle chains in bulk polymers}, volume={245}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000324303604513&KeyUID=WOS:000324303604513}, journal={Abstracts of Papers of the American Chemical Society}, author={Krommenhoek, Peter J. and Spontak, Richard J. and Tracy, Joseph B.}, year={2013} }
 @article{tracy_crawford_2013, title={Magnetic field-directed self-assembly of magnetic nanoparticles}, volume={38}, ISSN={["1938-1425"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000330345500017&KeyUID=WOS:000330345500017}, DOI={10.1557/mrs.2013.233}, abstractNote={Abstract}, number={11}, journal={MRS BULLETIN}, author={Tracy, Joseph B. and Crawford, Thomas M.}, year={2013}, month={Nov}, pages={915–920} }
 @article{oldenburg_chhetri_cooper_wu_troester_tracy_2013, title={Motility-, autocorrelation-, and polarization-sensitive optical coherence tomography discriminates cells and gold nanorods within 3D tissue cultures}, volume={38}, ISSN={["0146-9592"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000322576200085&KeyUID=WOS:000322576200085}, DOI={10.1364/ol.38.002923}, abstractNote={We propose a method for differentiating classes of light scatterers based upon their temporal and polarization properties computed from time series of polarization-sensitive optical coherence tomography (PS-OCT) images. The amplitude (motility) and time scale (autocorrelation decay time) of the speckle fluctuations are combined with the cross-polarization pixel-wise to render Motility-, autocorrelation-, and polarization-sensitive (MAPS) OCT contrast images. This combination of metrics provides high specificity for discriminating diffusive gold nanorods and mammary epithelial cell spheroids within 3D tissue culture, based on their unique MAPS signature. This has implications toward highly specific contrast in molecular (nanoparticle-based) and functional (cellular activity) imaging using standard PS-OCT hardware.}, number={15}, journal={OPTICS LETTERS}, author={Oldenburg, Amy L. and Chhetri, Raghav K. and Cooper, Jason M. and Wu, Wei-Chen and Troester, Melissa A. and Tracy, Joseph B.}, year={2013}, month={Aug}, pages={2923–2926} }
 @article{medford_johnston-peck_tracy_2013, title={Nanostructural transformations during the reduction of hollow and porous nickel oxide nanoparticles}, volume={5}, ISSN={["2040-3372"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000313347200017&KeyUID=WOS:000313347200017}, DOI={10.1039/c2nr33005a}, abstractNote={Size-dependent nanostructural transformations occurring during the H(2)-mediated reduction of hollow and porous NiO nanoparticles were investigated for controlled nanoparticle sizes of ~10 to 100 nm. Transmission electron microscopy reveals that the location and number of reduction sites strongly depend on the nanoparticle size and structure.}, number={1}, journal={NANOSCALE}, author={Medford, John A. and Johnston-Peck, Aaron C. and Tracy, Joseph B.}, year={2013}, pages={155–159} }
 @article{zhu_tracy_dong_jiang_jones_childers_2013, title={Teaching a Multidisciplinary Nanotechnology Laboratory Course to Undergraduate Students}, volume={5}, ISSN={1936-7449}, url={http://dx.doi.org/10.1166/jne.2013.1032}, DOI={10.1166/jne.2013.1032}, abstractNote={Here we report our efforts to teach the first multidisciplinary undergraduate nanotechnology laboratory course in the College of Engineering at North Carolina State University (NCSU). The course was designed to provide undergraduate students with hands-on experience in nanoscience and nanotechnology. The theme of this laboratory course is the integration of nanotechnology with microsystem technology, i.e., bottom-up synthesis meeting top-down fabrication. This course consists of seven carefully designed lab modules that bridge the major “pillars” of nanotechnology– nanomaterials, nanofabrication, nanoscale characterization, and nanodevices. Final projects provide students opportunities to conduct nanotechnology research through problem-based learning and to improve their communication and presentation skills for educating the public about nanotechnology. A pedagogical approach that features problem-based learning, group learning, visual/tactile assistance and interdisciplinary interaction was employed during the offering of this course.}, number={1}, journal={Journal of Nano Education}, publisher={American Scientific Publishers}, author={Zhu, Yong and Tracy, Joseph B. and Dong, Jingyan and Jiang, Xiaoning and Jones, M. Gail and Childers, Gina}, year={2013}, month={Jun}, pages={17–26} }
 @article{pearce_railsback_anderson_sarac_mcknight_tracy_melechko_2013, title={Transfer of Vertically Aligned Carbon Nanofibers to Polydimethylsiloxane (PDMS) While Maintaining their Alignment and Impalefection Functionality}, volume={5}, ISSN={["1944-8252"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000315079700055&KeyUID=WOS:000315079700055}, DOI={10.1021/am302501z}, abstractNote={Vertically aligned carbon nanofibers (VACNFs) are synthesized on Al 3003 alloy substrates by direct current plasma-enhanced chemical vapor deposition. Chemically synthesized Ni nanoparticles were used as the catalyst for growth. The Si-containing coating (SiN(x)) typically created when VACNFs are grown on silicon was produced by adding Si microparticles prior to growth. The fiber arrays were transferred to PDMS by spin coating a layer on the grown substrates, curing the PDMS, and etching away the Al in KOH. The fiber arrays contain many fibers over 15 μm (long enough to protrude from the PDMS film and penetrate cell membranes) and SiN(x) coatings as observed by SEM, EDX, and fluorescence microscopy. The free-standing array in PDMS was loaded with pVENUS-C1 plasmid and human brain microcapillary endothelial (HBMEC) cells and was successfully impalefected.}, number={3}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Pearce, Ryan C. and Railsback, Justin G. and Anderson, Bryan D. and Sarac, Mehmet F. and McKnight, Timothy E. and Tracy, Joseph B. and Melechko, Anatoli V.}, year={2013}, month={Feb}, pages={878–882} }
 @article{krommenhoek_wang_hentz_johnston-peck_kozek_kalyuzhny_tracy_2012, title={Bulky Adamantanethiolate and Cyclohexanethiolate Ligands Favor Smaller Gold Nanoparticles with Altered Discrete Sizes}, volume={6}, ISSN={["1936-0851"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000305661300037&KeyUID=WOS:000305661300037}, DOI={10.1021/nn3003778}, abstractNote={Use of bulky ligands (BLs) in the synthesis of metal nanoparticles (NPs) gives smaller core sizes, sharpens the size distribution, and alters the discrete sizes. For BLs, the highly curved surface of small NPs may facilitate growth, but as the size increases and the surface flattens, NP growth may terminate when the ligand monolayer blocks BLs from transporting metal atoms to the NP core. Batches of thiolate-stabilized Au NPs were synthesized using equimolar amounts of 1-adamantanethiol (AdSH), cyclohexanethiol (CySH), or n-hexanethiol (C6SH). The bulky CyS- and AdS-stabilized NPs have smaller, more monodisperse sizes than the C6S-stabilized NPs. As the bulkiness increases, the near-infrared luminescence intensity increases, which is characteristic of small Au NPs. Four new discrete sizes were measured by MALDI-TOF mass spectrometry, Au(30)(SAd)(18), Au(39)(SAd)(23), Au(65)(SCy)(30), and Au(67)(SCy)(30). No Au(25)(SAd)(18) was observed, which suggests that this structure would be too sterically crowded. Use of BLs may also lead to the discovery of new discrete sizes in other systems.}, number={6}, journal={ACS NANO}, author={Krommenhoek, Peter J. and Wang, Junwei and Hentz, Nathaniel and Johnston-Peck, Aaron C. and Kozek, Krystian A. and Kalyuzhny, Gregory and Tracy, Joseph B.}, year={2012}, month={Jun}, pages={4903–4911} }
 @article{halbur_krommenhoek_everitt_tracy_jur_2012, title={Enabling of nanoparticle application and function on the surface of fibrous textiles by atomic layer deposition}, volume={243}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000324475104033&KeyUID=WOS:000324475104033}, journal={Abstracts of Papers of the American Chemical Society}, author={Halbur, Jonathan and Krommenhoek, Peter J. and Everitt, Henry O. and Tracy, Joseph B. and Jur, Jesse S.}, year={2012} }
 @article{kozek_kozek_wu_tracy_2012, title={Large-scale synthesis of gold nanorods through continuous secondary growth}, volume={244}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000324621802217&KeyUID=WOS:000324621802217}, journal={Abstracts of Papers of the American Chemical Society}, author={Kozek, Krystian A. and Kozek, Klaudia M. and Wu, Wei-Chen and Tracy, Joseph B.}, year={2012} }
 @article{jie_niskala_johnston-peck_krommenhoek_tracy_fan_you_2012, title={Laterally patterned magnetic nanoparticles}, volume={22}, ISSN={["1364-5501"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000298970700034&KeyUID=WOS:000298970700034}, DOI={10.1039/c1jm14612b}, abstractNote={Laterally patterning magnetic nanoparticles (MNPs) through self-assembly and simple solution processing constitutes an important step toward inexpensive nanoparticle-based devices. In this work, MNPs were laterally patterned on metal thin films using laterally patterned self-assembled monolayers (SAMs) as a template. SAMs of inactive molecules were first patterned on an Au thin film using the soft-lithographic technique, microcontact printing. The active, bifunctional molecules, 1,10-decanedithiol or 4-(11-mercaptoundecyl)benzene-1,2-diol, were then patterned through backfilling. The MNPs selectively bind to the terminal thiols or modified catechols when the substrates are submerged into a solution of MNPs. By adjusting the deposition conditions, both monolayers and partial multilayers were controllably formed. Co, Ni, Fe3O4, and FePt MNPs, as well as Au non-magnetic nanoparticles were successfully patterned by this process. This generalized approach is anticipated to be adaptable to many other kinds of nanoparticlesvia judicious selection of the substrates, surfactant ligands (on the nanoparticle), and/or surface-bound monolayers.}, number={5}, journal={JOURNAL OF MATERIALS CHEMISTRY}, author={Jie, Yanni and Niskala, Jeremy R. and Johnston-Peck, Aaron C. and Krommenhoek, Peter J. and Tracy, Joseph B. and Fan, Huiqing and You, Wei}, year={2012}, pages={1962–1968} }
 @article{kozek_roskov_wu_chhetri_oldenburg_spontak_tracy_2012, title={Long-range alignment of gold nanorods in electrospun polymer nano/microfibers}, volume={243}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000324475104032&KeyUID=WOS:000324475104032}, journal={Abstracts of Papers of the American Chemical Society}, author={Kozek, Krystian A. and Roskov, Kristen E. and Wu, Wei-Chen and Chhetri, Raghav K. and Oldenburg, Amy L. and Spontak, Richard J. and Tracy, Joseph B.}, year={2012} }
 @article{johnston-peck_tracy_2012, title={Phase transformation of alumina-coated FePt nanoparticles}, volume={111}, ISSN={["1089-7550"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000303282400219&KeyUID=WOS:000303282400219}, DOI={10.1063/1.3676419}, abstractNote={Monolayers of FePt nanoparticles (NPs) were coated with 10 nm-thick layers of Al2O3 by pulsed laser deposition (PLD). The Al2O3 coating prevents diffusion and stabilizes the NP monolayer against sintering. Annealing converts the FePt NPs from an alloy phase (A1) into intermetallic phases. Atomic resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) shows that Pt-rich A1 Fe29Pt71 NPs convert into the FePt3 L12 intermetallic phase upon annealing and develop faceted morphologies. HAADF-STEM also reveals the presence of structural defects and Pt-rich shells. These results, in conjunction with prior studies of Al2O3 deposition by atomic layer deposition (ALD), demonstrate that coating arrays of FePt NPs with thin Al2O3 films by PLD or ALD imparts thermal stability and provides comparable results.}, number={7}, journal={JOURNAL OF APPLIED PHYSICS}, author={Johnston-Peck, Aaron C. and Tracy, Joseph B.}, year={2012}, month={Apr} }
 @article{wang_krommenhoek_bradford_gong_tracy_parsons_luo_zhu_2011, title={Coating Alumina on Catalytic Iron Oxide Nanoparticles for Synthesizing Vertically Aligned Carbon Nanotube Arrays}, volume={3}, ISSN={1944-8244 1944-8252}, url={http://dx.doi.org/10.1021/am201082m}, DOI={10.1021/am201082m}, abstractNote={To synthesize long and uniform vertically aligned carbon nanotube (VACNT) arrays, it is essential to use catalytic nanoparticles (NPs) with monodisperse sizes and to avoid NP agglomeration at the growth temperature. In this work, VACNT arrays were grown on chemically synthesized Fe(3)O(4) NPs of diameter 6 nm by chemical vapor deposition. Coating the NPs with a thin layer of Al(2)O(3) prior to CNT growth preserves the monodisperse sizes, resulting in uniform, thick and dense VACNT arrays. Comparison with uncoated NPs shows that the Al(2)O(3) coating effectively prevents the catalyst NPs from sintering and coalescing, resulting in improved control over VACNT growth.}, number={11}, journal={ACS Applied Materials & Interfaces}, publisher={American Chemical Society (ACS)}, author={Wang, Xin and Krommenhoek, Peter J. and Bradford, Philip D. and Gong, Bo and Tracy, Joseph B. and Parsons, Gregory N. and Luo, Tzy-Jiun M. and Zhu, Yuntian T.}, year={2011}, month={Oct}, pages={4180–4184} }
 @article{sarac_wilson_johnston-peck_wang_pearce_klein_melechko_tracy_2011, title={Effects of Ligand Monolayers on Catalytic Nickel Nanoparticles for Synthesizing Vertically Aligned Carbon Nanofibers}, volume={3}, ISSN={["1944-8244"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000289762400003&KeyUID=WOS:000289762400003}, DOI={10.1021/am101290v}, abstractNote={Vertically aligned carbon nanofibers (VACNFs) were synthesized using ligand-stabilized Ni nanoparticle (NP) catalysts and plasma-enhanced chemical vapor deposition. Using chemically synthesized Ni NPs enables facile preparation of VACNF arrays with monodisperse diameters below the size limit of thin film lithography. During pregrowth heating, the ligands catalytically convert into graphitic shells that prevent the catalyst NPs from agglomerating and coalescing, resulting in a monodisperse VACNF size distribution. In comparison, significant agglomeration occurs when the ligands are removed before VACNF growth, giving a broad distribution of VACNF sizes. The ligand shells are also promising for patterning the NPs and synthesizing complex VACNF arrays.}, number={4}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Sarac, Mehmet F. and Wilson, Robert M. and Johnston-Peck, Aaron C. and Wang, Junwei and Pearce, Ryan and Klein, Kate L. and Melechko, Anatoli V. and Tracy, Joseph B.}, year={2011}, month={Apr}, pages={936–940} }
 @article{johnston-peck_wang_tracy_2011, title={Formation and Grain Analysis of Spin-Cast Magnetic Nanoparticle Monolayers}, volume={27}, ISSN={["0743-7463"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000289321000097&KeyUID=WOS:000289321000097}, DOI={10.1021/la200005q}, abstractNote={Ligand-stabilized magnetic nanoparticles (NPs) with diameters of 4-7 nm were spin-cast into monolayers on electron-transparent silicon nitride (SiN) substrates. SiN membranes facilitate detailed high-resolution characterization of the spin-cast monolayers by transmission electron microscopy (TEM) and approximate spin-casting onto wafers. Suspending the NPs in hexanes and pretreating the substrate with ultraviolet light and ozone (UVO) gives the best results. Computer-aided analysis of the arrays elucidates their grain structures, including identification of the grain boundaries and defects and measurements of the grain orientations and translational correlation lengths. Narrow NP size distributions result in close-packed arrays with minimal defects and large grains containing thousands of NPs. Edge dislocations, interstitials, vacancies, and overlapping NPs were observed. Deviations from close packing occur as the normalized standard deviation of the sample's size distribution increases above approximately 11%. Polydisperse size distributions and deviations from spherical NP shapes frustrate assembly and prevent ordered packing.}, number={8}, journal={LANGMUIR}, author={Johnston-Peck, Aaron C. and Wang, Junwei and Tracy, Joseph B.}, year={2011}, month={Apr}, pages={5040–5046} }
 @article{rachtman_jung_johnston-peck_tracy_kalyuzhny_2011, title={H-1, C-13 and P-31 NMR study of precursor evolution in the synthesis of magic-size II-VI semiconductor nanocrystals}, volume={241}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000291982801308&KeyUID=WOS:000291982801308}, journal={Abstracts of Papers of the American Chemical Society}, author={Rachtman, Eleonora and Jung, Minho and Johnston-Peck, Aaron C. and Tracy, Joseph B. and Kalyuzhny, Gregory}, year={2011} }
 @article{chhetri_kozek_johnston-peck_tracy_oldenburg_2011, title={Imaging three-dimensional rotational diffusion of plasmon resonant gold nanorods using polarization-sensitive optical coherence tomography}, volume={83}, ISSN={["1550-2376"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000289521900001&KeyUID=WOS:000289521900001}, DOI={10.1103/physreve.83.040903}, abstractNote={We demonstrate depth-resolved viscosity measurements within a single object using polarized optical scattering from ensembles of freely tumbling plasmon resonant gold nanorods (GNRs) monitored with polarization-sensitive optical coherence tomography. The rotational diffusion coefficient of the GNRs is shown to correlate with viscosity in molecular fluids according to the Stokes-Einstein relation. The plasmon resonant and highly anisotropic properties of GNRs are favorable for microrheological studies of nanoscale properties.}, number={4}, journal={PHYSICAL REVIEW E}, author={Chhetri, Raghav K. and Kozek, Krystian A. and Johnston-Peck, Aaron C. and Tracy, Joseph B. and Oldenburg, Amy L.}, year={2011}, month={Apr} }
 @article{roskov_kozek_wu_chhetri_oldenburg_spontak_tracy_2011, title={Long-Range Alignment of Gold Nanorods in Electrospun Polymer Nano/Microfibers}, volume={27}, ISSN={0743-7463 1520-5827}, url={http://dx.doi.org/10.1021/la2021066}, DOI={10.1021/la2021066}, abstractNote={In this study, a scalable fabrication technique for controlling and maintaining the nanoscale orientation of gold nanorods (GNRs) with long-range macroscale order has been achieved through electrospinning. The volume fraction of GNRs with an average aspect ratio of 3.1 is varied from 0.006 to 0.045 in aqueous poly(ethylene oxide) solutions to generate electrospun fibers possessing different GNR concentrations and measuring 40-3000 nm in diameter. The GNRs within these fibers exhibit excellent alignment with their longitudinal axis parallel to the fiber axis n. According to microscopy analysis, the average deviant angle between the GNR axis and n increases modestly from 3.8 to 13.3° as the fiber diameter increases. Complementary electron diffraction measurements confirm preferred orientation of the {100} GNR planes. Optical absorbance spectroscopy measurements reveal that the longitudinal surface plasmon resonance bands of the aligned GNRs depend on the polarization angle and that maximum extinction occurs when the polarization is parallel to n.}, number={23}, journal={Langmuir}, publisher={American Chemical Society (ACS)}, author={Roskov, Kristen E. and Kozek, Krystian A. and Wu, Wei-Chen and Chhetri, Raghav K. and Oldenburg, Amy L. and Spontak, Richard J. and Tracy, Joseph B.}, year={2011}, month={Dec}, pages={13965–13969} }
 @article{johnston-peck_scarel_wang_parsons_tracy_2011, title={Order-Disorder Phase Conversion of FePt Nanoparticles for Ultrahigh-Density Magnetic Recording}, volume={17}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927611010026}, DOI={10.1017/S1431927611010026}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in  Nashville, Tennessee, USA, August 7–August 11, 2011.}, number={S2}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Johnston-Peck, A and Scarel, G and Wang, J and Parsons, G and Tracy, J}, year={2011}, month={Jul}, pages={1830–1831} }
 @article{kozek_johnston-peck_wang_tracy_2011, title={Silver nanoparticles stabilized by sterically-bulky ligands}, volume={242}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000299378304116&KeyUID=WOS:000299378304116}, journal={Abstracts of Papers of the American Chemical Society}, author={Kozek, Krystian A. and Johnston-Peck, Aaron C. and Wang, Junwei and Tracy, Joseph B.}, year={2011} }
 @article{johnston-peck_scarel_wang_parsons_tracy_2011, title={Sinter-free phase conversion and scanning transmission electron microscopy of FePt nanoparticle monolayers}, volume={3}, ISSN={["2040-3372"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000295618200024&KeyUID=WOS:000295618200024}, DOI={10.1039/c1nr10567a}, abstractNote={Thermally robust monolayers of 4-6 nm diameter FePt nanoparticles (NPs) were fabricated by combining chemical synthesis and atomic layer deposition. Spin-cast monolayers of FePt NPs were coated with thin, 11 nm-thick layers of amorphous Al(2)O(3), followed by annealing to convert the FePt NPs from an alloy (A1) into intermetallic FePt (L1(0)) and FePt(3) (L1(2)) phases. The Al(2)O(3) layer serves as a barrier that prevents sintering between NPs during annealing at temperatures up to 730 °C. Electron and X-ray diffraction in conjunction with high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) show that as-synthesized A1 FePt NPs convert into L1(0) and L1(2) phase NPs through annealing. HAADF-STEM measurements of individual NPs reveal imperfect ordering and show that the NP composition determines which intermetallic phase is obtained. Mixed-phase NPs with L1(0) cores and FePt(3) L1(2) shells were also observed, as well as a smaller number of unconverted A1 NPs. These results highlight the need for improved control over the compositional uniformity of FePt NPs for their use in bit-patterned magnetic recording.}, number={10}, journal={NANOSCALE}, author={Johnston-Peck, Aaron C. and Scarel, Giovanna and Wang, Junwei and Parsons, Gregory N. and Tracy, Joseph B.}, year={2011}, pages={4142–4149} }
 @article{gong_johnston-peck_tracy_kalyuzhny_2011, title={Synthesis and optical properties of nanocrystals, nanowires, and nanoplates of ZnSe and ZnTe}, volume={241}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000291982801309&KeyUID=WOS:000291982801309}, journal={Abstracts of Papers of the American Chemical Society}, author={Gong, Ke and Johnston-Peck, Aaron C. and Tracy, Joseph B. and Kalyuzhny, Gregory}, year={2011} }
 @article{shore_wang_johnston-peck_oldenburg_tracy_2011, title={Synthesis of Au(Core)/Ag(Shell) Nanoparticles and their Conversion to AuAg Alloy Nanoparticles}, volume={7}, ISSN={["1613-6829"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000286997600011&KeyUID=WOS:000286997600011}, DOI={10.1002/smll.201001138}, abstractNote={Metal nanoparticles (NPs) are of great interest due to their special optical, [ 1–3 ] electronic, [ 4–8 ] and catalytic [ 9,10 ] properties. [ 11 ] Among metal NPs, Au NPs have been investigated most extensively because of their facile preparation, resistance to oxidation, and surface plasmon resonance (SPR) band that can absorb and scatter visible light. [ 3 ] Core/ shell and alloy bimetallic NPs are especially interesting because they provide opportunities to tune the NPs’ optical and catalytic properties [ 12–15 ] and are potentially useful as taggants for security applications. [ 2 ] The AuAg system is of particular interest because the SPR band is tunable between ∼ 520 nm for Au [ 11 ] and ∼ 410 nm for Ag. [ 16 ] Several syntheses for AuAg alloy, [ 15 , 17–37 ] Au(core)/Ag(shell), [ 22 , 25 , 31 , 33 , 35–45 ] and Ag(core)/Au(shell) NPs [ 28 , 31 , 33–35 , 42 , 46–48 ] have already been reported. Here, we report a facile, stoichiometrically controlled synthesis of Au(core)/Ag(shell) and AuAg alloy NPs through digestive ripening, [ 49–51 ] which is a potentially general method for synthesizing alloy NPs. [ 37 , 52,53 ] Au(core)/Ag(shell) NPs were synthesized and annealed to form AuAg alloy NPs, followed by elemental analysis and structural and optical characterization. Methods utilizing Au rather than Ag NPs as the seed particles are advantageous: obtaining monodisperse Ag NPs is signifi cantly more challenging [ 16 ] because it is harder to control the nucleation of Ag NPs and to avoid oxidation. Huang and co-workers recently demonstrated the conversion of Au(core)/Ag(shell) to AuAg alloy NPs as a part of a larger study showing the generality of digestive ripening for synthesizing alloy NPs, but very limited data without quantitative elemental analysis or optical characterization of the AuAg alloy NPs was provided. [ 37 ] In this study, we compare a twostep synthesis of Au(core)/Ag(shell) NPs and their conversion to AuAg alloy NPs through annealing with a one-step, direct conversion of Au NPs to AuAg alloy NPs. The products of}, number={2}, journal={SMALL}, author={Shore, Matthew S. and Wang, Junwei and Johnston-Peck, Aaron C. and Oldenburg, Amy L. and Tracy, Joseph B.}, year={2011}, month={Jan}, pages={230–234} }
 @article{marusak_johnston-peck_tracy_2011, title={Synthesis of ligand-stabilized CoNi nanoparticles with tunable sizes and compositions}, volume={242}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000299378304115&KeyUID=WOS:000299378304115}, journal={Abstracts of Papers of the American Chemical Society}, author={Marusak, Katherine E. and Johnston-Peck, Aaron C. and Tracy, Joseph B.}, year={2011} }
 @article{tracy_2010, title={Chemical and nanostructural transformations during reactions of metal nanoparticles}, volume={240}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000208164700437&KeyUID=WOS:000208164700437}, journal={Abstracts of Papers of the American Chemical Society}, author={Tracy, Joseph B.}, year={2010} }
 @article{weil_wang_tracy_van benthem_2010, title={Determination of Local Oxidations States in Ni-NiO Core-shell Structures Using White Line Intensity Ratios}, volume={16}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927610060411}, DOI={10.1017/S1431927610060411}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.}, number={S2}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Weil, SM and Wang, J and Tracy, JB and van Benthem, K}, year={2010}, month={Jul}, pages={1458–1459} }
 @article{railsback_johnston-peck_wang_tracy_2010, title={Size-Dependent Nanoscale Kirkendall Effect During the Oxidation of Nickel Nanoparticles}, volume={4}, ISSN={["1936-086X"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000276956800020&KeyUID=WOS:000276956800020}, DOI={10.1021/nn901736y}, abstractNote={The transformation of Ni nanoparticles (NPs) of different sizes (average diameters of 9, 26, and 96 nm) during oxidation to hollow (single void) or porous (multiple voids) NiO through the nanoscale Kirkendall effect was observed by transmission electron microscopy. Samples treated for 1-4 h at 200-500 degrees C show that the structures of the completely oxidized NPs do not depend on the temperature, but oxidation proceeds more quickly at elevated temperatures. For the Ni/NiO system, after formation of an initial NiO shell (of thickness approximately 3 nm), single or multiple voids nucleate on the inner surface of the NiO shell, and the voids grow until conversion to NiO is complete. Differences in the void formation and growth processes cause size-dependent nanostructural evolution: For 9 and 26 nm NPs, a single void forms beneath the NiO shell, and the void grows by moving across the NP while conversion to NiO occurs opposite the site where the void initially formed. Because of the differences in the Ni/NiO volume ratios for the 9 and 26 nm NPs when the void first forms, they have distinct nanostructures: The 9 nm NPs form NiO shells that are nearly radially symmetric, while there is a pronounced asymmetry in the NiO shells for 26 nm NPs. By choosing an intermediate oxidation temperature and varying the reaction time, partially oxidized Ni(core)/NiO(shell) NPs can be synthesized with good control. For 96 nm NPs, multiple voids form and grow, which results in porous NiO NPs.}, number={4}, journal={ACS NANO}, author={Railsback, Justin G. and Johnston-Peck, Aaron C. and Wang, Junwei and Tracy, Joseph B.}, year={2010}, month={Apr}, pages={1913–1920} }
 @article{johnston-peck_wang_tracy_2009, title={COLL 111-Formation and grain analysis of magnetic nanoparticle monolayers}, volume={238}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000207861903465&KeyUID=WOS:000207861903465}, journal={Abstracts of Papers of the American Chemical Society}, author={Johnston-Peck, Aaron C. and Wang, Junwei and Tracy, Joseph B.}, year={2009} }
 @article{wang_johnston-peck_tracy_2009, title={Nickel Phosphide Nanoparticles with Hollow, Solid, and Amorphous Structures}, volume={21}, ISSN={["1520-5002"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000270461700018&KeyUID=WOS:000270461700018}, DOI={10.1021/cm901073k}, abstractNote={Conversion of unary metal nanoparticles (NPs) upon exposure to oxygen, sulfur, selenium, and phophorus precursors usually produces hollow metal oxide, sulfide, selenide, or phosphide NPs through the Kirkendall effect. Here, nanostructural control of mixed-phase Ni2P/Ni12P5 (represented as NixPy) NPs prepared through the thermolysis of nickel acetylacetonate using trioctylphosphine (TOP) as a ligand and phosphorus precursor is reported. The P:Ni molar ratio controls the NP size and is the key factor in determining the nanostructure. For P:Ni molar ratios of 1−3, nickel NPs form below 240 °C and subsequently convert to crystalline-hollow NixPy NPs at 300 °C. For higher P:Ni ratios, a Ni-TOP complex forms that requires higher temperatures for NP growth, thus favoring direct formation of NixPy rather than nickel. Consequently, for P:Ni molar ratios of >9, amorphous-solid NixPy NPs form at 240 °C and become crystalline-solid NixPy NPs at 300 °C. For intermediate P:Ni molar ratios of ∼6, both growth mechanisms ...}, number={19}, journal={CHEMISTRY OF MATERIALS}, author={Wang, Junwei and Johnston-Peck, Aaron C. and Tracy, Joseph B.}, year={2009}, month={Oct}, pages={4462–4467} }
 @article{johnston-peck_wang_tracy_2009, title={Synthesis and Structural and Magnetic Characterization of Ni(Core)/NiO(Shell) Nanoparticles}, volume={3}, ISSN={["1936-086X"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000266323600007&KeyUID=WOS:000266323600007}, DOI={10.1021/nn900019x}, abstractNote={A size series of ligand-stabilized Ni nanoparticles (NPs) with diameters between 8-24 nm was prepared by solution chemistry, followed by solution-phase oxidation with atmospheric oxygen at 200 degrees C to form Ni(core)/NiO(shell) NPs with shell thicknesses of 2-3 nm. In comparison with the oxidation of Fe and Co NPs, Ni NPs require higher temperatures for significant conversion to NiO. Transmission electron microscopy and electron diffraction show polycrystalline cores with predominantly amorphous shells. SQUID magnetometry measurements were performed to assess the effects of coupling between the ferromagnetic Ni cores and antiferromagnetic NiO shells. After intentional oxidation, the Ni(core)/NiO(shell) NPs have decreased superparamagnetic blocking temperatures (T(B)) and no exchange shift (H(EB)), but a small enhancement in the coercivity (H(C)) signifies weak exchange bias. These effects originate from the amorphous structure of the NiO shells and their thin layer thickness that renders the NiO moments incapable of pinning the core moment in moderate applied fields. The magnetocrystalline anisotropy constants before and after oxidation approach the value for bulk Ni and depend on the Ni core size and NiO shell thickness.}, number={5}, journal={ACS NANO}, author={Johnston-Peck, Aaron C. and Wang, Junwei and Tracy, Joseph B.}, year={2009}, month={May}, pages={1077–1084} }
 @article{fields-zinna_sampson_crowe_tracy_parker_deney_muddiman_murray_2009, title={Tandem Mass Spectrometry of Thiolate-Protected Au Nanoparticles NaxAu25(SC2H4Ph)(18-y)(S(C2H4O)(5)CH3)(y)}, volume={131}, ISSN={["0002-7863"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000270186600057&KeyUID=WOS:000270186600057}, DOI={10.1021/ja905787y}, abstractNote={We report the first collision-induced dissociation tandem mass spectrometry (CID MS/MS) of a thiolate-protected Au nanoparticle that has a crystallographically determined structure. CID spectra assert that dissociation pathways for the mixed monolayer Na(x)Au(25)(SC(2)H(4)Ph)(18-y)(S(C(2)H(4)O)(5)CH(3))(y) centrally involve the semi-ring Au(2)L(3) coordination (L = some combination of the two thiolate ligands) that constitutes the nanoparticle's protecting structure. The data additionally confirm charge state assignments in the mass spectra. Prominent among the fragments is [Na(2)AuL(2)](1+), one precursor of which is identified as another nanoparticle fragment in the higher m/z region. Another detected fragment, [Na(2)Au(2)L(3)](1+), represents a mass loss equivalent to an entire semi-ring, whereas others suggest involvement (fragmentation/rearrangement) of multiple semi-rings, e.g., [NaAu(3)L(3)](1+) and [NaAu(4)L(4)](1+). The detailed dissociation/rearrangement mechanisms of these species are not established, but they are observed in other mass spectrometry experiments, including those under non-CID conditions, namely, electrospray ionization mass spectrometry (ESI-MS) with both time-of-flight (TOF) and FT-ICR analyzers. The latter, previously unreported results show that even soft ionization sources can result in Au nanoparticle fragmentation, including that yielding Au(4)L(4) in ESI-TOF of a much larger thiolate-protected Au(144) nanoparticle under non-CID conditions.}, number={38}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Fields-Zinna, Christina A. and Sampson, Jason S. and Crowe, Matthew C. and Tracy, Joseph B. and Parker, Joseph F. and deNey, Alexander M. and Muddiman, David C. and Murray, Royce W.}, year={2009}, month={Sep}, pages={13844–13851} }
 @article{dass_guo_tracy_balasubramanian_douglas_murray_2008, title={Gold nanoparticles with perfluorothiolate ligands}, volume={24}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000251916100046&KeyUID=WOS:000251916100046}, DOI={10.1021/la702651y}, abstractNote={Two syntheses of gold nanoparticles with fluorinated alkyl and aryl thiolate ligands are reported. The fluorous Au nanoparticles are smaller than previous gold fluor-capped examples, and are in the 44-75 Au atom size range. Fluoroalkyl thiolate-protected (1H,1H,2H,2H-perfluorodecanethiolate) nanoparticles synthesized by a Brust reaction are a mixture of (mainly) approximately 8.5 kDa (ca. 44 core atoms) and approximately 14 kDa (ca. 75 core atoms) species, by MALDI-mass spectrometry. This composition is consistent with thermogravimetric analysis (TGA) results of the ligand shell composition. 19F NMR spectra display a progressive line broadening of resonances for fluorine sites closer to the Au core. A second synthetic route used a (ligand replacement) reaction of pentafluorobenzenethiol with Au55(PPh3)12Cl6. The exchange is (as previously observed for nonfluorinated thiols) accompanied by nanoparticle core size changes to produce a polydisperse mixture within which a Au75 core species could be electrochemically discerned by its characteristic 0.74 V electrochemical energy gap. Further characterization of the polydisperse nanoparticle product was done by HPLC, TEM, TGA, optical spectroscopy, and NMR data. Both varieties of fluorous nanoparticles exhibit solubilities typical of perfluorinated materials, as opposed to proteo versions.}, number={1}, journal={LANGMUIR}, author={DASS, A and GUO, R and TRACY, JB and BALASUBRAMANIAN, R and DOUGLAS, AD and MURRAY, RW}, year={2008}, pages={310–315} }
 @article{wang_johnston-peck_tracy_2008, title={INOR 620-Exchange bias and the magnetic properties of oxidized nickel nanoparticles}, volume={236}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000270256306531&KeyUID=WOS:000270256306531}, journal={ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY}, author={WANG, JW and JOHNSTON-PECK, AC and TRACY, JB}, year={2008} }
 @article{insin_tracy_lee_zimmer_westervelt_bawendi_2008, title={Incorporation of iron oxide nanoplarticles and quantum dots into silica microspheres}, volume={2}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000253503300008&KeyUID=WOS:000253503300008}, DOI={10.1021/nn700344x}, abstractNote={We describe the synthesis of magnetic and fluorescent silica microspheres fabricated by incorporating maghemite (gamma-Fe2O3) nanoparticles (MPs) and CdSe/CdZnS core/shell quantum dots (QDs) into a silica shell around preformed silica microspheres. The resultant approximately 500 nm microspheres have a narrow size distribution and show uniform incorporation of QDs and MPs into the shell. We have demonstrated manipulation of these microspheres using an external magnetic field with real-time fluorescence microscopy imaging.}, number={2}, journal={ACS NANO}, author={INSIN, N and TRACY, JB and LEE, H and ZIMMER, JP and WESTERVELT, RM and BAWENDI, MG}, year={2008}, pages={197–202} }
 @article{tracy_2008, title={NUCL 27-Magnetic and metallic monolayer-protected nanoparticles}, volume={236}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000270256305758&KeyUID=WOS:000270256305758}, journal={ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY}, author={TRACY, JB}, year={2008} }
 @article{dass_stevenson_dubay_tracy_murray_2008, title={Nanoparticle MALDI-TOF mass spectrometry without fragmentation: Au-25(SCH2CH2Ph)(18) and mixed monolayer Au-25(SCH2CH2Ph)(18-x)(L)(x)}, volume={130}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000255629400033&KeyUID=WOS:000255629400033}, DOI={10.1021/ja710323t}, abstractNote={Intact molecular ions of the organothiolate-protected nanoparticle Au25(SCH2CH2Ph)18, including their isotopic resolution, can be observed at 7391 Da as 1- and 1+ ions in negative and positive mode, respectively, by MALDI-TOF mass spectrometry when using a tactic of threshold laser pulse intensities and trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB) as matrix. Previous MALDI-TOF studies of Au nanoparticles using other matrices have encountered extensive fragmentation of nanoparticle as well as thiolate ligands. Absence of fragmentation enables precise determination of the distribution of mixed monolayer compositions on nanoparticles prepared by ligand exchange reactions and by synthesis using thiol mixtures. Reaction conditions producing mixed monolayers containing only one or a small number of usefully functional ligands can be readily identified. At increased laser pulse intensity, the first fragmentation step(s) for the Au25(SCH 2CH2Ph)18 nanoparticle results in losses of AuL units and, in particular, loss of Au4(SCH2CH2Ph)4.}, number={18}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={DASS, A and STEVENSON, A and DUBAY, GR and TRACY, JB and MURRAY, RW}, year={2008}, pages={5940–5946} }
 @article{carney_devries_dubois_kim_kim_singh_ghorai_tracy_stiles_murray_et al._2008, title={Size limitations for the formation of ordered striped nanoparticles}, volume={130}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000252426300010&KeyUID=WOS:000252426300010}, DOI={10.1021/ja077383m}, abstractNote={A combination of immiscible molecules in the ligand shell of a gold nanoparticle (NP) has been shown to phase separate into a rippled structure; this phase separation can be used to direct the assembly of the NPs into chains. Here we demonstrate that only NPs within a certain size range can form chains, and we conclude that the rippled morphology of the ligand shell also exists only within that given size range. We corroborate this result with simulations of the ligand arrangement on NPs of various sizes.}, number={3}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={CARNEY, RP and DEVRIES, GA and DUBOIS, C and KIM, H and KIM, JY and SINGH, C and GHORAI, PK and TRACY, JB and STILES, RL and MURRAY, RW and et al.}, year={2008}, pages={798-+} }
 @article{tracy_crowe_fields-zinna_parker_kalyuzhny_menard_balasubramanian_choi_nuzzo_murray_2007, title={COLL 242-Nanoparticle-based optical probes for chemical imaging}, volume={233}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000207722801352&KeyUID=WOS:000207722801352}, journal={Abstracts of Papers of the American Chemical Society}, author={Tracy, JB and Crowe, MC and Fields-Zinna, CA and Parker, JF and Kalyuzhny, G and Menard, LD and Balasubramanian, R and Choi, JP and Nuzzo, RG and Murray, RW}, year={2007} }
 @article{dass_gao_balasubramanian_douglas_tracy_murray_2007, title={COLL 270-Fluorinated gold thiolate nanoparticles by Brust synthesis and ligand exchange}, volume={234}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000207593902137&KeyUID=WOS:000207593902137}, journal={Abstracts of Papers of the American Chemical Society}, author={Dass, A and Gao, R and Balasubramanian, R and Douglas, AD and Tracy, JB and Murray, RW}, year={2007} }
 @article{tracy_crowe_parker_hampe_fields-zinna_dass_murray_2007, title={Electrospray ionization mass spectrometry of uniform and mixed monolayer nanoparticles: Au-25[S(CH2)(2)Ph](18) and Au-25[S(CH2)(2)Ph](18-x)(SR)(x)}, volume={129}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000251974000075&KeyUID=WOS:000251974000075}, DOI={10.1021/ja076621a}, abstractNote={New approaches to electrospray ionization mass spectrometry (ESI-MS)-with exact compositional assignments-of small (Au25) nanoparticles with uniform and mixed protecting organothiolate monolayers are described. The results expand the scope of analysis and reveal a rich chemistry of ionization behavior. ESI-MS of solutions of phenylethanethiolate monolayer-protected gold clusters (MPCs), Au25(SC2Ph)18, containing alkali metal acetate salts (MOAc) produce spectra in which, for Na+, K+, Rb+, and Cs+ acetates, the dominant species are MAu25(SC2Ph)182+ and M2Au25(SC2Ph)182+. Li+ acetates caused ligand loss. This method was extended to the analysis of Au25 MPCs with mixed monolayers, where thiophenolate (-SPh), hexanethiolate (-SC6), or biotinylated (-S-PEG-biotin) ligands had been introduced by ligand exchange. In negative-mode ESI-MS, no added reagents were needed in order to observe Au25(SC2Ph)18- and to analyze mixed monolayer Au25 MPCs prepared by ligand exchange with 4-mercaptobenzoic acid, HSPhCOOH, which gave spectra through deprotonation of the carboxylic acids. Adducts of tetraoctylammonium (Oct4N+) with -SPhCOO- sites were also observed. Mass spectrometry is the only method that has demonstrated capacity for measuring the exact distribution of ligand-exchange products. The possible origins of the different Au25 core charges (1-, 0, 1+, 2+) observed during electrospray ionization are discussed.}, number={51}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={TRACY, JB and CROWE, MC and PARKER, JF and HAMPE, O and FIELDS-ZINNA, CA and DASS, A and MURRAY, RW}, year={2007}, pages={16209–16215} }
 @article{wolfe_balasubramanian_tracy_murray_2007, title={Fully ferrocenated hexanethiolate monolayer-protected gold clusters}, volume={23}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000243990200093&KeyUID=WOS:000243990200093}, DOI={10.1021/la0624081}, abstractNote={The synthesis and compositional analysis of four different gold clusters with protecting monolayers comprised solely of ferrocene hexanethiolate ligands is described. The gold nanoparticles have average core diameters of 1.4, 1.6, 2.0, and 2.2 nm with estimated average atom counts of 55, 140, 225, and 314 Au atoms and average monolayer coverages of 37, 39, 43, and 58 ferrocenated ligands, respectively. The data show unequivocally that the number of ferrocene hexanethiolate ligands bound to each core size is constrained by the steric requirements of the ferrocene head group; the ligand numbers are significantly smaller than those for hexanethiolate ligands bonded to analogous-sized Au cores. Voltammetry of dilute solutions of these nanoparticles shows a large ferrocene oxidation wave and, at more negative potentials, smaller one-electron waves for the quantized double-layer charging of the Au cores. Together, the ferrocenes and core of the ferrocenated Au314 nanoparticle deliver 60 electrons at the ferrocene oxidation potential, which amounts to a very large volume charge capacity, 7x10(9) C/m3, for an undiluted nanoparticle sample.}, number={4}, journal={LANGMUIR}, author={WOLFE, RL and BALASUBRAMANIAN, R and TRACY, JB and MURRAY, RW}, year={2007}, pages={2247–2254} }
 @article{insin_tracy_lee_zimmer_westervelt_bawendi_2007, title={INOR 434-Incorporation of magnetic nanoparticles and quantum dots into silica microspheres}, volume={234}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000207593909610&KeyUID=WOS:000207593909610}, journal={Abstracts of Papers of the American Chemical Society}, author={Insin, N and Tracy, JB and Lee, H and Zimmer, JP and Westervelt, RM and Bawendi, MG}, year={2007} }
 @article{tracy_kalyuzhny_crowe_balasubramanian_choi_murray_2007, title={Poly(ethylene glycol) ligands for high-resolution nanoparticle mass spectrometry}, volume={129}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000246686700022&KeyUID=WOS:000246686700022}, DOI={10.1021/ja071042r}, abstractNote={Measurements of the core and ligand monolayer compositions of small gold nanoparticles (NPs) using electrospray ionization (ESI) mass spectrometry were performed by incorporating ionization tags, methoxy penta(ethylene glycol) thiolate ligands (-S-PEG), into the ligand monolayers via ligand exchange. During ESI, alkali metal ions (M+) coordinate to the -S-PEG ligands and give the NPs positive charge. Atomically precise, high-resolution measurements show unequivocally that the NP composition is Au25(ligand)18. The predominant ions, M4Au25(ligand)183+ and M5Au25(ligand)184+, have 1− charge on the core. Because ligand exchange is a statistical process, there is a distribution of mixed-monolayer exchange products, which is reflected in the mass spectra.}, number={21}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={TRACY, JB and KALYUZHNY, G and CROWE, MC and BALASUBRAMANIAN, R and CHOI, JP and MURRAY, RW}, year={2007}, pages={6706-+} }
 @article{fields-zinna_tracy_crowe_murray_2007, title={Preparation and characterization of bimetal thiolate monolayer protected clusters (MPCs)}, volume={234}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000207593902362&KeyUID=WOS:000207593902362}, journal={Abstracts of Papers of the American Chemical Society}, author={Fields-Zinna, CA and Tracy, JB and Crowe, MC and Murray, RW}, year={2007} }
 @article{branham_douglas_mills_tracy_white_murray_2006, title={Arylthiolate-protected silver quantum dots}, volume={22}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000242771200078&KeyUID=WOS:000242771200078}, DOI={10.1021/la062329p}, abstractNote={This paper describes a new, organic-soluble 4-tert-butylbenzyl mercaptan (BBT) monolayer-protected silver cluster (AgBBT MPC) as the first example of a dissolved silver nanoparticle that exhibits quantized one-electron double layer charging (QDL) voltammetry. Polydisperse AgBBT MPCs made by two different synthetic protocols, but with similar average core diameters (2.1 nm), exhibit sharply differing electrochemistry and optical absorbance spectra. A two-phase procedure (organic/aqueous, termed Prep A-AgBBT) produced MPCs exhibiting a 475 nm surface plasmon absorbance and QDL voltammetry. Neither property was seen for MPCs made by a single-phase procedure, termed Prep B-AgBBT. The difference is thought to reflect poor passivation to oxide formation in the latter Prep B procedure, which is supported by X-ray photoelectron spectroscopy results. Thermogravimetry, mass spectra, and electrochemistry results suggest an average stoichiometric formula of Ag140BBT53, but transmission electron microscopy shows that the products are also polydisperse and include polycrystalline aggregates. Dry, cast films of both Ag MPC preparations on interdigitated array electrodes exhibit low electron hopping conductivity, compared to Au MPCs.}, number={26}, journal={LANGMUIR}, author={BRANHAM, MR and DOUGLAS, AD and MILLS, AJ and TRACY, JB and WHITE, PS and MURRAY, RW}, year={2006}, pages={11376–11383} }
 @article{tracy_kalyuzhny_menard_balasubramanian_choi_crowe_nuzzo_murray_2006, title={COLL 236-Characterization of small Au monolayer protected clusters using electrospray mass spectrometry}, volume={232}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000207781603512&KeyUID=WOS:000207781603512}, journal={Abstracts of Papers of the American Chemical Society}, author={Tracy, Joseph B. and Kalyuzhny, Gregory and Menard, Laurent D. and Balasubramanian, R. and Choi, Jai-Pil and Crowe, Matthew C. and Nuzzo, Ralph G. and Murray, Royce W.}, year={2006} }
 @article{tracy_kalyuzhny_menard_balasubramanian_choi_crowe_nuzzo_murray_2006, title={Chemistry of metal and metal oxide nanoparticles: Characterization of small Au nanoparticles using electrospray mass spectrometry}, volume={232}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000207781600016&KeyUID=WOS:000207781600016}, journal={Abstracts of Papers of the American Chemical Society}, author={Tracy, Joseph B. and Kalyuzhny, Gregory and Menard, Laurent D. and Balasubramanian, R. and Choi, Jai-Pil and Crowe, Matthew C. and Nuzzo, Ralph G. and Murray, Royce W.}, year={2006}, pages={18} }
 @article{tracy_bawendi_2006, title={Defects in CoO in oxidized cobalt nanoparticles dominate exchange biasing and exhibit anomalous magnetic properties}, volume={74}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000242409100080&KeyUID=WOS:000242409100080}, DOI={10.1103/PhysRevB.74.184434}, abstractNote={Defects can vastly modify the optical, electrical, mechanical, and magnetic properties of materials. In this paper, we report an investigation of the magnetic properties of moments associated with defects in CoO in partially and fully oxidized colloidal Co nanoparticles. The defect moments freeze at low temperature and have a distribution of melting temperatures, in which most melt below $50\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, but exchange biasing (EB) generated by the CoO lattice stabilizes the Co core moments in the partially oxidized sample up to $170\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ [J. B. Tracy, D. N. Weiss, D. P. Dinega, and M. G. Bawendi, Phys. Rev. B 72, 064404 (2005)]. By switching the polarity of the biasing field at intermediate temperatures during cooling, we show that the defect moments dominate EB at low temperature and exhibit a thermal memory effect. Selected cooling sequences show that the exchange shift (${H}_{\mathit{EB}}$) may change sign as the sample is heated and demonstrate tuning of ${H}_{\mathit{EB}}$ and the coercivity. Thermal remanent magnetization measurements directly show how changes in the orientation of CoO defect moments cause the Co core moments to reorient. An investigation of the temporal stability of the defect moments is also reported.}, number={18}, journal={PHYSICAL REVIEW B}, author={TRACY, JB and BAWENDI, MG}, year={2006} }
 @inproceedings{kim_zimmer_ohnishi_tracy_frangioni_bawendi_2006, title={Engineering InAsxP1-x/InP/ZnSe III-V alloyed core/shell quantum dots for the near infrared}, volume={231}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000238125905210&KeyUID=WOS:000238125905210}, booktitle={231st National Meeting of the American-Chemical-Society}, author={KIM, SW and ZIMMER, JP and OHNISHI, S and TRACY, JB and FRANGIONI, JV and BAWENDI, MG}, year={2006} }
 @inproceedings{tracy_bawendi_2005, title={Defects in CoO dominate exchange biasing in Co(core)/CoO(shell) nanoparticles.}, volume={229}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000228177707104&KeyUID=WOS:000228177707104}, booktitle={229th National Meeting of the American-Chemical-Society}, author={TRACY, JB and BAWENDI, MG}, year={2005}, pages={U976} }
 @article{kim_zimmer_ohnishi_tracy_frangioni_bawendi_2005, title={Engineering InAsxP1-x/InP/ZnSe III−V Alloyed Core/Shell Quantum Dots for the Near-Infrared}, volume={127}, ISSN={0002-7863 1520-5126}, url={http://dx.doi.org/10.1021/ja0434331}, DOI={10.1021/ja0434331}, abstractNote={Quantum dots with a core/shell/shell structure consisting of an alloyed core of InAs(x)P(1-x), an intermediate shell of InP, and an outer shell of ZnSe were developed. The InAs(x)P(1-x) alloyed core has a graded internal composition with increasing arsenic content from the center to the edge of the dots. This compositional gradient results from two apparent effects: (1) the faster reaction kinetics of the phosphorus precursor compared to the arsenic precursor, and (2) a post-growth arsenic-phosphorus exchange reaction that increases the arsenic content. The cores have a zinc blend structure for all compositions and show tunable emission in the near-infrared (NIR) region. A first shell of InP leads to a red-shift and an increase in quantum yield. The final shell of ZnSe serves to stabilize the dots for applications in aqueous environments, including NIR biomedical fluorescence imaging. These NIR-emitting core/shell/shell InAs(x)P(1-x)/InP/ZnSe were successfully used in a sentinel lymph node mapping experiment.}, number={30}, journal={Journal of the American Chemical Society}, publisher={American Chemical Society (ACS)}, author={Kim, Sang-Wook and Zimmer, John P. and Ohnishi, Shunsuke and Tracy, Joseph B. and Frangioni, John V. and Bawendi, Moungi G.}, year={2005}, month={Aug}, pages={10526–10532} }
 @article{tracy_weiss_dinega_bawendi_2005, title={Exchange biasing and magnetic properties of partially and fully oxidized colloidal cobalt nanoparticles}, volume={72}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000231564400071&KeyUID=WOS:000231564400071}, DOI={10.1103/PhysRevB.72.064404}, abstractNote={Colloidal magnetic nanoparticles (NPs) have been applied in magnetic separations, in medicine and in biochemistry. They are also potentially applicable in magnetic recording media. In this paper, we report a systematic investigation of the magnetic properties of colloidal Co NPs after three extents of oxidation. The native sample has a thin (1.0 nm) CoO shell and exhibits no exchange biasing. The purposefully partially oxidized sample has a thicker CoO shell (3.2 nm), and is exchange biased. The sample fully oxidized to CoO loses exchange biasing. We observe three distinct magnetic properties that result from the finite-thickness antiferromagnet shell exchange coupled to a finite-size ferromagnet core, and from crystal and stoichiometric defects: (1) an enhancement of the thermal stability of the orientation of the magnetic moment due to exchange biasing in the partially oxidized sample, (2) a low-temperature paramagnetic response in the partially and fully oxidized samples due to defects in the CoO shell, and (3) an asymmetry in the field-dependent magnetization for the partially oxidized sample at low temperature due to small clusters of Co in a diffusion layer around the Co core. We propose a simple model to interpret these effects.}, number={6}, journal={PHYSICAL REVIEW B}, author={TRACY, JB and WEISS, DN and DINEGA, DP and BAWENDI, MG}, year={2005} }
 @article{kim_kim_tracy_jasanoff_bawendi_2005, title={Phosphine Oxide Polymer for Water-Soluble Nanoparticles}, volume={127}, ISSN={0002-7863 1520-5126}, url={http://dx.doi.org/10.1021/ja043577f}, DOI={10.1021/ja043577f}, abstractNote={A phosphine oxide polymer was developed using bis(dichlorophosphino)ethane and poly(ethylene glycol). This polymer system was used to transfer various nanoparticles from organic solvents to water, retaining their physical properties and reactivities.}, number={13}, journal={Journal of the American Chemical Society}, publisher={American Chemical Society (ACS)}, author={Kim, Sang-Wook and Kim, Sungjee and Tracy, Joseph B. and Jasanoff, Alan and Bawendi, Moungi G.}, year={2005}, month={Apr}, pages={4556–4557} }
 @article{kim_kim_tracy_jasanoff_bawendi_2005, title={Phosphine oxide polymer for water-soluble nanoparticles}, volume={127}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000228089300007&KeyUID=WOS:000228089300007}, DOI={10.1021/ja043511f}, number={13}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={KIM, SW and KIM, S and TRACY, JB and JASANOFF, A and BAWENDI, MG}, year={2005}, pages={4556–4557} }
 @article{hennrich_lebedkin_malik_tracy_barczewski_rosner_kappes_2002, title={Preparation, characterization and applications of free-standing single walled carbon nanotube thin films}, volume={4}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000175708800035&KeyUID=WOS:000175708800035}, DOI={10.1039/b201570f}, abstractNote={A method for the reliable fabrication of less than 200 nm thick, free-standing purified-SWNT films having large surface areas exceeding several cm2 is described. Films were characterized using a variety of optical, microscopic and spectroscopic methods. The procedure was also used to prepare thin films of as-prepared, acid-cut and octadecylamine (ODA) functionalized SWNTs. Such samples allow facile transmission measurements of SWNT derived solids.}, number={11}, journal={PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, author={HENNRICH, F and LEBEDKIN, S and MALIK, S and TRACY, J and BARCZEWSKI, M and ROSNER, H and KAPPES, M}, year={2002}, pages={2273–2277} }
 @article{veirs_conradson_clark_keogh_neu_reilly_runde_palmer_tracy_1999, title={The effect of oxidation state and speciation on XANES spectra of plutonium.}, volume={217}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000079148200192&KeyUID=WOS:000079148200192}, journal={ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY}, author={VEIRS, DK and CONRADSON, SD and CLARK, DL and KEOGH, DW and NEU, MP and REILLY, SD and RUNDE, W and PALMER, PD and TRACY, JB}, year={1999}, pages={U59} }