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Full-Text Articles in Nanoscience and Nanotechnology

Substrate–Support Interactions Mediate Hydrogenation Of Phenolic Compounds By Pd/Ceo2 Nanorods, Yeongseo An, Pranjali Naik, Igor I. Slowing, Vincenzo Venditti Nov 2020

Substrate–Support Interactions Mediate Hydrogenation Of Phenolic Compounds By Pd/Ceo2 Nanorods, Yeongseo An, Pranjali Naik, Igor I. Slowing, Vincenzo Venditti

Chemistry Publications

Ceria-supported palladium (Pd/CeO2) has spawned significant attention in recent years due to its ability to catalyze selective hydrogenation of phenolic compounds to cyclohexanones and cyclohexanols at a mild temperature and pressure. However, the mechanistic basis by which ceria enhances catalytic conversion is still unclear. Here, we use the increase in the 13C transverse relaxation rate upon the addition of nanoparticles (NPs) (13C ΔR2) to investigate the adsorption of phenolic compounds on the surface of the Pd/CeO2 catalyst by solution NMR. We show that hydroxyphenols adsorb on the support more efficiently than underivatized phenol and methoxyphenols and ...


Mxenes As Flow Electrodes For Capacitive Deionization Of Wastewater, Naqsh E. Mansoor Aug 2020

Mxenes As Flow Electrodes For Capacitive Deionization Of Wastewater, Naqsh E. Mansoor

Boise State University Theses and Dissertations

The energy-water nexus poses an integrated research challenge, while opening up an opportunity space for the development of energy efficient technologies for water remediation. Capacitive Deionization (CDI) is an upcoming reclamation technology that uses a small applied voltage applied across electrodes to electrophoretically remove dissolved ionic impurities from wastewater streams. Similar to a supercapacitor, the ions are stored in the electric double layer of the electrodes. Reversing the polarity of applied voltage enables recovery of the removed ionic impurities, allowing for recycling and reuse. Simultaneous materials recovery and water reclamation makes CDI energy efficient and resource conservative, with potential to ...


Reshaping Of Truncated Pd Nanocubes: Energetic And Kinetic Analysis Integrating Transmission Electron Microscopy With Atomistic-Level And Coarse-Grained Modeling, King C. Lai, Minda Chen, Benjamin Williams, Yong Han, Chia-Kuang Tsung, Wenyu Huang, James W. Evans Jul 2020

Reshaping Of Truncated Pd Nanocubes: Energetic And Kinetic Analysis Integrating Transmission Electron Microscopy With Atomistic-Level And Coarse-Grained Modeling, King C. Lai, Minda Chen, Benjamin Williams, Yong Han, Chia-Kuang Tsung, Wenyu Huang, James W. Evans

Chemistry Publications

Stability against reshaping of metallic fcc nanocrystals synthesized with tailored far-from-equilibrium shapes is key to maintaining optimal properties for applications such as catalysis. Yet Arrhenius analysis of experimental reshaping kinetics, and appropriate theory and simulation, is lacking. Thus, we use TEM to monitor the reshaping of Pd nanocubes of ∼25 nm side length between 410 °C (over ∼4.5 h) and 440 °C (over ∼0.25 h), extracting a high effective energy barrier of Eeff ≈ 4.6 eV. We also provide an analytic determination of the energy variation along the optimal pathway for reshaping that involves transfer of atoms across ...


Surface Chemistry Of Ternary Nanocrystals: Engineering The Deposition Of Conductive Nabis2 Films, Alan M. Medina-Gonzalez, Bryan A. Rosales, Umar H. Hamdeh, Matthew G. Panthani, Javier Vela Jun 2020

Surface Chemistry Of Ternary Nanocrystals: Engineering The Deposition Of Conductive Nabis2 Films, Alan M. Medina-Gonzalez, Bryan A. Rosales, Umar H. Hamdeh, Matthew G. Panthani, Javier Vela

Chemistry Publications

The ability to engineer the surface chemistry of complex ternary nanocrystals is critical to their successful application in photovoltaic, thermoelectric, and other energy conversion devices. For many years, several studies have shed light into the surface chemistry of unary and binary semiconductor nanocrystals, as well as their surface modification with monodentate and multidentate ligands in a variety of applications. In contrast, our understanding of the surface chemistry and ligand modification of ternary and other complex multinary nanocrystals remains relatively limited. Recently, our group reported the synthesis of colloidal NaBiS2 semiconductor nanocrystals with sizes tunable between 2–60 nm, and a ...


Facile Fabrication Of Hierarchical Mof–Metal Nanoparticle Tandem Catalysts For The Synthesis Of Bioactive Molecules, Jingwen Chen, Biying Zhang, Long Qi, Yuchen Pei, Renfeng Nie, Patrick M. Heintz, Xuechen Luan, Zongbi Bao, Qiwei Yang, Qilong Ren, Zhiguo Zhang, Wenyu Huang May 2020

Facile Fabrication Of Hierarchical Mof–Metal Nanoparticle Tandem Catalysts For The Synthesis Of Bioactive Molecules, Jingwen Chen, Biying Zhang, Long Qi, Yuchen Pei, Renfeng Nie, Patrick M. Heintz, Xuechen Luan, Zongbi Bao, Qiwei Yang, Qilong Ren, Zhiguo Zhang, Wenyu Huang

Chemistry Publications

Multifunctional metal–organic frameworks (MOFs) that possess permanent porosity are promising catalysts in organic transformation. Herein, we report the construction of a hierarchical MOF functionalized with basic aliphatic amine groups and polyvinylpyrrolidone-capped platinum nanoparticles (Pt NPs). The postsynthetic covalent modification of organic ligands increases basic site density in the MOF and simultaneously introduces mesopores to create a hierarchically porous structure. The multifunctional MOF is capable of catalyzing a sequential Knoevenagel condensation–hydrogenation–intramolecular cyclization reaction. The unique selective reduction of the nitro group to intermediate hydroxylamine by Pt NPs supported on MOF followed by intramolecular cyclization with a cyano group ...


Crystallographic Facet Selective Her Catalysis: Exemplified In Fep And Nip2 Single Crystals, Bryan Owens-Baird, Juliana P.S. Sousa, Yasmine Ziouani, Dmitri Y. Petrovykh, Nikolai A. Zarkevich, Duane D. Johnson, Yury V. Kolen'ko, Kirill Kovnir Apr 2020

Crystallographic Facet Selective Her Catalysis: Exemplified In Fep And Nip2 Single Crystals, Bryan Owens-Baird, Juliana P.S. Sousa, Yasmine Ziouani, Dmitri Y. Petrovykh, Nikolai A. Zarkevich, Duane D. Johnson, Yury V. Kolen'ko, Kirill Kovnir

Ames Laboratory Accepted Manuscripts

How the crystal structures of ordered transition-metal phosphide catalysts affect the hydrogen-evolution reaction (HER) is investigated by measuring the anisotropic catalytic activities of selected crystallographic facets on large (mm-sized) single crystals of iron-phosphide (FeP) and monoclinic nickel-diphosphide (m-NiP2). We find that different crystallographic facets exhibit distinct HER activities, in contrast to a commonly held assumption of severe surface restructuring during catalytic activity. Moreover, density-functional-theory-based computational studies show that the observed facet activity correlates well with the H-binding energy to P atoms on specific surface terminations. Direction dependent catalytic properties of two different phosphides with different transition metals, crystal structures, and ...


Intermetallic Nanocatalysts From Heterobimetallic Group 10–14 Pyridine-2-Thiolate Precursors, Carena L. Daniels, Megan Knobeloch, Philip Yox, Marquix A.S. Adamson, Yunhua Chen, Rick W. Dorn, Hao Wu, Guoquan Zhou, Huajun Fan, Aaron J. Rossini, Javier Vela Mar 2020

Intermetallic Nanocatalysts From Heterobimetallic Group 10–14 Pyridine-2-Thiolate Precursors, Carena L. Daniels, Megan Knobeloch, Philip Yox, Marquix A.S. Adamson, Yunhua Chen, Rick W. Dorn, Hao Wu, Guoquan Zhou, Huajun Fan, Aaron J. Rossini, Javier Vela

Chemistry Publications

Intermetallic compounds are atomically ordered inorganic materials containing two or more transition metals and main-group elements in unique crystal structures. Intermetallics based on group 10 and group 14 metals have shown enhanced activity, selectivity, and durability in comparison to simple metals and alloys in many catalytic reactions. While high-temperature solid-state methods to prepare intermetallic compounds exist, softer synthetic methods can provide key advantages, such as enabling the preparation of metastable phases or of smaller particles with increased surface areas for catalysis. Here, we study a generalized family of heterobimetallic precursors to binary intermetallics, each containing a group 10 metal and ...


The Surface Termination Of Cspbbr3 Perovskite Quantum Dots Determined By Solid-State Nmr Spectroscopy, Yunhua Chen, Sara R. Smock, Anne H. Flintgruber, Frederic A. Perras, Richard L. Brutchey, Aaron J. Rossini Mar 2020

The Surface Termination Of Cspbbr3 Perovskite Quantum Dots Determined By Solid-State Nmr Spectroscopy, Yunhua Chen, Sara R. Smock, Anne H. Flintgruber, Frederic A. Perras, Richard L. Brutchey, Aaron J. Rossini

Chemistry Publications

Cesium lead halide perovskite quantum dots (QDs) have gained significant attention as next-generation optoelectronic materials; however, their properties are highly dependent on their surface chemistry. The surfaces of cuboidal CsPbBr3 QDs have been intensively studied by both theoretical and experimental techniques, but fundamental questions still remain about the atomic termination of the QDs. The binding sites and modes of ligands at the surface remain unproven. Herein, we demonstrate that solid-state NMR spectroscopy allows the unambiguous assignments of organic surface ligands via 1H, 13C, and 31P NMR. Surface-selective 133Cs solid-state NMR spectra show the presence of an additional 133Cs NMR signal ...


Identifying The Molecular Edge Termination Of Exfoliated Hexagonal Boron Nitride Nanosheets With Solid-State Nmr Spectroscopy And Plane-Wave Dft Calculations, Rick W. Dorn, Matthew J. Ryan, Tae-Hoon Kim, Tian Wei Goh, Patrick M. Heintz, Lin Zhou, Wenyu Huang, Aaron J. Rossini Feb 2020

Identifying The Molecular Edge Termination Of Exfoliated Hexagonal Boron Nitride Nanosheets With Solid-State Nmr Spectroscopy And Plane-Wave Dft Calculations, Rick W. Dorn, Matthew J. Ryan, Tae-Hoon Kim, Tian Wei Goh, Patrick M. Heintz, Lin Zhou, Wenyu Huang, Aaron J. Rossini

Chemistry Publications

Hexagonal boron nitride nanosheets (h-BNNS), the isoelectronic analog to graphene, have received interest over the past decade due to their high thermal oxidative resistance, high bandgap, catalytic activity, and low cost. The functional groups that terminate boron and nitrogen zigzag and/or armchair edges directly affect their chemical, physical, and electronic properties. However, an understanding of the molecular edge termination present in h-BNNS is lacking. Here, high-resolution magic-angle spinning (MAS) solid-state NMR (SSNMR) spectroscopy, and plane-wave density-functional theory (DFT) calculations are used to determine the molecular edge termination in exfoliated h-BNNS. 1H → 11B cross-polarization MAS (CPMAS) SSNMR ...


Shapes Of Fe Nanocrystals Encapsulated At The Graphite Surface, Ann Lii-Rosales, Yong Han, Scott E. Julien, Olivier Pierre-Louis, Dapeng Jing, Kai-Tak Wan, Michael C. Tringides, James W. Evans, Patricia A. Thiel Feb 2020

Shapes Of Fe Nanocrystals Encapsulated At The Graphite Surface, Ann Lii-Rosales, Yong Han, Scott E. Julien, Olivier Pierre-Louis, Dapeng Jing, Kai-Tak Wan, Michael C. Tringides, James W. Evans, Patricia A. Thiel

Chemistry Publications

We describe and analyze in detail the shapes of Fe islands encapsulated under the top graphene layers in graphite. Shapes are interrogated using scanning tunneling microscopy. The main outputs of the shape analysis are the slope of the graphene membrane around the perimeter of the island, and the aspect ratio of the central metal cluster. Modeling primarily uses a continuum elasticity (CE) model. As input to the CE model, we use density functional theory to calculate the surface energy of Fe, and the adhesion energies between Fe and graphene or graphite. We use the shaft-loaded blister test (SLBT) model to ...


Nanoscale Colocalization Of Fluorogenic Probes Reveals The Role Of Oxygen Vacancies In The Photocatalytic Activity Of Tungsten Oxide Nanowires, Meikun Shen, Tianben Ding, Steven T. Hartman, Fudong Wang, Christina Krucylak, Zheyu Wang, Che Tan, Bo Yin, Rohan Mishra, Matthew D. Lew, Bryce Sadtler Jan 2020

Nanoscale Colocalization Of Fluorogenic Probes Reveals The Role Of Oxygen Vacancies In The Photocatalytic Activity Of Tungsten Oxide Nanowires, Meikun Shen, Tianben Ding, Steven T. Hartman, Fudong Wang, Christina Krucylak, Zheyu Wang, Che Tan, Bo Yin, Rohan Mishra, Matthew D. Lew, Bryce Sadtler

Electrical & Systems Engineering Publications and Presentations

Defect engineering is a strategy that has been widely used to design active semiconductor photocatalysts. However, understanding the role of defects, such as oxygen vacancies, in controlling photocatalytic activity remains a challenge. Here, we report the use of chemically triggered fluorogenic probes to study the spatial distribution of active regions in individual tungsten oxide nanowires using super-resolution fluorescence microscopy. The nanowires show significant heterogeneity along their lengths for the photocatalytic generation of hydroxyl radicals. Through quantitative, coordinate-based colocalization of multiple probe molecules activated by the same nanowires, we demonstrate that the nanoscale regions most active for the photocatalytic generation of ...


Identification Of An Ags2 Complex On Ag(110), Peter M. Spurgeon, Da-Jiang Liu, Junepyo Oh, Yousoo Kim, Patricia A. Thiel Dec 2019

Identification Of An Ags2 Complex On Ag(110), Peter M. Spurgeon, Da-Jiang Liu, Junepyo Oh, Yousoo Kim, Patricia A. Thiel

Chemistry Publications

Adsorbed sulfur has been investigated on the Ag(110) surface at two different coverages, 0.02 and 0.25 monolayers. At the lower coverage, only sulfur adatoms are present. At the higher coverage, there are additional bright features which we identify as linear, independent AgS2 complexes. This identification is based upon density functional theory (DFT) and its comparison with experimental observations including bias dependence and separation between complexes. DFT also predicts the absence of AgS2 complexes at low coverage, and the development of AgS2 complexes around a coverage of 0.25 monolayers of sulfur, as is experimentally observed. To our ...


Highly Reactive Energetic Films By Pre-Stressing Nano-Aluminum Particles, Michael N. Bello, Alan M. Williams, Valery I. Levitas, Nobumichi Tamura, Daniel K. Unruh, Juliusz Warzywoda, Michelle L. Pantoya Dec 2019

Highly Reactive Energetic Films By Pre-Stressing Nano-Aluminum Particles, Michael N. Bello, Alan M. Williams, Valery I. Levitas, Nobumichi Tamura, Daniel K. Unruh, Juliusz Warzywoda, Michelle L. Pantoya

Aerospace Engineering Publications

Energetic films were synthesized using stress altered nano-aluminum particles (nAl). The nAl powder was pre-stressed to examine how modified mechanical properties of the fuel particles influenced film reactivity. Pre-stressing conditions varied by quenching rate. Slow and rapid quenching rates induced elevated dilatational strain within the nAl particles that was measured using synchrotron X-ray diffraction (XRD). An analytical model for stress and strain in a nAl core–Al2O3 shell particle that includes creep in the shell and delamination at the core–shell boundary, was developed and used for interpretation of strain measurements. Results show rapid quenching induced 81% delamination at the ...


Fabricating Fe Nanocrystals Via Encapsulation At The Graphite Surface, Ana Lii-Rosales, Yong Han, King C. Lai, Dapeng Jing, Michael C. Tringides, James W. Evans, Patricia A. Thiel Nov 2019

Fabricating Fe Nanocrystals Via Encapsulation At The Graphite Surface, Ana Lii-Rosales, Yong Han, King C. Lai, Dapeng Jing, Michael C. Tringides, James W. Evans, Patricia A. Thiel

Chemistry Publications

In this paper, the authors describe the conditions under which Fe forms encapsulated nanocrystals beneath the surface of graphite, and they characterize these islands (graphite + Fe) thoroughly. The authors use the experimental techniques of scanning tunneling microscopy (STM) plus x-ray photoelectron spectroscopy (XPS) and the computational technique of density functional theory (DFT). Necessary conditions for encapsulation are preexisting ion-induced defects in the graphite substrate and elevated deposition temperature of 875–900 K. Evidence of encapsulation consists of atomically resolved STM images of a carbon lattice, both on top of the islands and on the sloping sides. The nature of the ...


Top-Down And Bottom-Up Fabrication Of Key Components In Miniature Energy Storage Devices, Wenhao Li Oct 2019

Top-Down And Bottom-Up Fabrication Of Key Components In Miniature Energy Storage Devices, Wenhao Li

Doctoral Dissertations

The advent of miniature electronic devices demands power sources of commensurate form factors. This spurs the research of micro energy storage devices, e.g., 3D microbatteries. A 3D microbattery contains nonplanar microelectrodes with high aspect ratio and high surface area, separated by a nanoscale electrolyte. The device takes up a total volume as small as 10 mm3, allowing it to serve on a chip and to provide power in-situ. The marriage of nanotechnology and electrochemical energy storage makes microbattery research a fascinating field with both scientific excitement and application prospect. However, successful fabrication of well-functioned key components and the ...


Novel Avenues Toward Controlling The Photophysical Properties Of Ultra-Small Silicon Quantum Dots, Mohammed Abdelhameed Oct 2019

Novel Avenues Toward Controlling The Photophysical Properties Of Ultra-Small Silicon Quantum Dots, Mohammed Abdelhameed

Electronic Thesis and Dissertation Repository

Quantum dots (QDs) have attracted an increasing attention in the last decade over many conventional organic dyes. This is due to their unique optical properties including broad absorption spectra, high photostability, and size-tunable photoluminescence (PL). However, some toxicity concerns associated with traditional quantum dots have hindered their wide applicability. Interestingly, silicon quantum dots (SQDs) have been shown to be more advantageous than most of QDs thanks to their excellent biocompatibility and biodegradability, low cytotoxicity, and versatile surface functionalization capability. Thus, SQDs are promising candidates for various biological and biomedical applications such as bioimaging, biosensing, and photodynamic therapy. Unfortunately, only a ...


Minimalistic Peptide-Based Supramolecular Systems Relevant To The Chemical Origin Of Life, Daniela Kroiss Sep 2019

Minimalistic Peptide-Based Supramolecular Systems Relevant To The Chemical Origin Of Life, Daniela Kroiss

Dissertations, Theses, and Capstone Projects

All forms of life are based on biopolymers, which are made up of a selection of simple building blocks, such as amino acids, nucleotides, fatty acids and sugars. Their individual properties govern their interactions, giving rise to complex supramolecular structures with highly specialized functionality, including ligand recognition, catalysis and compartmentalization. In this thesis, we aim to answer the question whether short peptides could have acted as precursors of modern proteins during prebiotic evolution. Using a combination of experimental and computational techniques, we screened a large molecular search space for peptide sequences that are capable of forming supramolecular complexes with adenosine ...


Unveiling The Photo‐ And Thermal‐Stability Of Cesium Lead Halide Perovskite Nanocrystals, Brett W. Boote, Himashi P. Andaraarachchi, Bryan A. Rosales, Rafael Blome-Fernández, Feng Zhu, Malinda D. Reichert, Kalyan Santra, Jingzhe Li, Jacob W. Petrich, Javier Vela, Emily A. Smith Aug 2019

Unveiling The Photo‐ And Thermal‐Stability Of Cesium Lead Halide Perovskite Nanocrystals, Brett W. Boote, Himashi P. Andaraarachchi, Bryan A. Rosales, Rafael Blome-Fernández, Feng Zhu, Malinda D. Reichert, Kalyan Santra, Jingzhe Li, Jacob W. Petrich, Javier Vela, Emily A. Smith

Chemistry Publications

Lead halide perovskites possess unique characteristics well‐suited for optoelectronic and energy capture devices, however, concerns about their long‐term stability remain. All‐inorganic CsPbX3 (X = Cl, Br, I) perovskite nanocrystals have been reported with improved stability. We investigate the photo‐ and thermal‐stability properties of CsPbX3 (X = Cl, Br, I) nanocrystals by electron microscopy, x‐ray diffraction, thermogravimetric analysis, ensemble and single particle spectral characterization. CsPbBr¬3 is stable under 1‐sun illumination for 16 h in ambient conditions, although single crystal analysis indicates the luminescence states change over time. CsPbBr¬3 is also stable to heating to 250 ...


Synthesis And Optical Properties Of Ordered-Vacancy Perovskite Cesium Bismuth Halide Nanocrystals, Rainie D. Nelson, Kalyan Santra, Y. Wang, Atefe Hadi, Jacob W. Petrich, Matthew G. Panthani Aug 2019

Synthesis And Optical Properties Of Ordered-Vacancy Perovskite Cesium Bismuth Halide Nanocrystals, Rainie D. Nelson, Kalyan Santra, Y. Wang, Atefe Hadi, Jacob W. Petrich, Matthew G. Panthani

Matthew Panthani

Perovskite-phase cesium bismuth halide (Cs3Bi2X9; X = Cl, Br, I) nanocrystals were synthesized using a hot-injection approach. These nanocrystals adopted ordered-vacancy perovskite crystal structures and demonstrated composition-tunable optical properties. Growth occurred by initial formation of Bi0 seeds, and morphology was controlled by precursor and seed concentration. The Cs3Bi2I9 nanocrystals demonstrated excellent stability under ambient conditions for several months. Contrary to previous reports, we find that photoluminescence originates from the precursor material as opposed to the Cs3Bi2X9 nanocrystals.


Stamped Multilayer Graphene Laminates For Disposable In-Field Electrodes: Application To Electrochemical Sensing Of Hydrogen Peroxide And Glucose, Loreen R. Stromberg, John A. Hondred, Delaney Sanborn, Deyny Mendivelso-Perez, Srikanthan Ramesh, Iris V. Rivero, Josh Kogot, Emily Smith, Carmen Gomes, Jonathan C. Claussen Aug 2019

Stamped Multilayer Graphene Laminates For Disposable In-Field Electrodes: Application To Electrochemical Sensing Of Hydrogen Peroxide And Glucose, Loreen R. Stromberg, John A. Hondred, Delaney Sanborn, Deyny Mendivelso-Perez, Srikanthan Ramesh, Iris V. Rivero, Josh Kogot, Emily Smith, Carmen Gomes, Jonathan C. Claussen

Mechanical Engineering Publications

A multi-step approach is described for the fabrication of multi-layer graphene-based electrodes without the need for ink binders or post-print annealing. Graphite and nanoplatelet graphene were chemically exfoliated using a modified Hummers’ method and the dried material was thermally expanded. Expanded materials were used in a 3D printed mold and stamp to create laminate electrodes on various substrates. The laminates were examined for potential sensing applications using model systems of peroxide (H2O2) and enzymatic glucose detection. Within the context of these two assay systems, platinum nanoparticle electrodeposition and oxygen plasma treatment were examined as methods for improving sensitivity. Electrodes made ...


Synthesis Of Germanium Nanocrystals From Solid-State Disproportionation Of A Chloride-Derived Germania Glass, Yujie Wang, Utkarsh Ramesh, Charles K. A. Nyamekye, Bradley J. Ryan, Rainie D. Nelson, Abdulla M. Alebri, Umar H. Hamdeh, Atefe Hadi, Emily A. Smith, Matthew G. Panthani Jun 2019

Synthesis Of Germanium Nanocrystals From Solid-State Disproportionation Of A Chloride-Derived Germania Glass, Yujie Wang, Utkarsh Ramesh, Charles K. A. Nyamekye, Bradley J. Ryan, Rainie D. Nelson, Abdulla M. Alebri, Umar H. Hamdeh, Atefe Hadi, Emily A. Smith, Matthew G. Panthani

Matthew Panthani

Germanium nanocrystals (Ge NCs) have potential to be used in several optoelectronic applications such as photodetectors and light-emitting diodes. Here, we report a solid-state route to synthesizing Ge NCs through thermal disproportionation of a germania (GeOX) glass, which was synthesized by hydrolyzing a GeCl2·dioxane complex. The GeOX glass synthesized in this manner was found to have residual Cl content. The process of nanocrystal nucleation and growth was monitored using powder X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. Compared to existing solid-state routes for synthesizing colloidal Ge NCs, this approach requires fewer steps and is amenable ...


Improving The Stability And Monodispersity Of Layered Cesium Lead Iodide Perovskite Thin Films By Tuning Crystallization Dynamics, Atefe Hadi, Bradley J. Ryan, Rainie D. Nelson, Kalyan Santra, Fang-Yi Lin, Eric W. Cochran, Matthew G. Panthani Jun 2019

Improving The Stability And Monodispersity Of Layered Cesium Lead Iodide Perovskite Thin Films By Tuning Crystallization Dynamics, Atefe Hadi, Bradley J. Ryan, Rainie D. Nelson, Kalyan Santra, Fang-Yi Lin, Eric W. Cochran, Matthew G. Panthani

Chemical and Biological Engineering Publications

Assembling halide perovskites into layered structures holds promise for addressing chemical and phase stability challenges; however, several other challenges need to be addressed to create efficient and stable halide perovskite devices. Layered halide perovskites (LHPs) suffer from broad distribution of layer thicknesses and bandgaps within thin films. Reducing polydispersity could substantially improve charge transport within LHP films and the performance of LHP-based solar cells. Herein, we focused on layering α-CsPbI3 ((C4H9NH3)2Csn-1PbnI3n+1) thin films. We found that (C4H9NH3)2Csn-1PbnI3n+1 with nominal layer thicknesses of n = 1, 2, 3, and 4 can be deposited at temperatures as low as ...


Reshaping, Intermixing, And Coarsening For Metallic Nanocrystals: Nonequilibrium Statistical Mechanical And Coarse-Grained Modeling, King C. Lai, Yong Han, Peter M. Spurgeon, Wenyu Huang, Patricia A. Thiel, Da-Jiang Liu, James W. Evans Jun 2019

Reshaping, Intermixing, And Coarsening For Metallic Nanocrystals: Nonequilibrium Statistical Mechanical And Coarse-Grained Modeling, King C. Lai, Yong Han, Peter M. Spurgeon, Wenyu Huang, Patricia A. Thiel, Da-Jiang Liu, James W. Evans

Chemistry Publications

Self-assembly of supported 2D or 3D nanocrystals (NCs) by vacuum deposition and of 3D NCs by solution-phase synthesis (with possible subsequent transfer to a support) produces intrinsically nonequilibrium systems. Individual NCs can have far-from-equilibrium shapes and composition profiles. The free energy of NC ensembles is lowered by coarsening which can involve Ostwald ripening or Smoluchowski ripening (NC diffusion and coalescence). Preservation of individual NC structure and inhibition of coarsening are key, e.g., for avoiding catalyst degradation. This review focuses on postsynthesis evolution of metallic NCs. Atomistic-level modeling typically utilizes stochastic lattice-gas models to access appropriate time and length scales ...


Synthesis Of Germanium Nanocrystals From Solid-State Disproportionation Of A Chloride-Derived Germania Glass, Yujie Wang, Utkarsh Ramesh, Charles K. A. Nyamekye, Bradley J. Ryan, Rainie D. Nelson, Abdulla M. Alebri, Umar H. Hamdeh, Atefe Hadi, Emily A. Smith, Matthew G. Panthani Apr 2019

Synthesis Of Germanium Nanocrystals From Solid-State Disproportionation Of A Chloride-Derived Germania Glass, Yujie Wang, Utkarsh Ramesh, Charles K. A. Nyamekye, Bradley J. Ryan, Rainie D. Nelson, Abdulla M. Alebri, Umar H. Hamdeh, Atefe Hadi, Emily A. Smith, Matthew G. Panthani

Chemical and Biological Engineering Publications

Germanium nanocrystals (Ge NCs) have potential to be used in several optoelectronic applications such as photodetectors and light-emitting diodes. Here, we report a solid-state route to synthesizing Ge NCs through thermal disproportionation of a germania (GeOX) glass, which was synthesized by hydrolyzing a GeCl2·dioxane complex. The GeOX glass synthesized in this manner was found to have residual Cl content. The process of nanocrystal nucleation and growth was monitored using powder X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. Compared to existing solid-state routes for synthesizing colloidal Ge NCs, this approach requires fewer steps and is amenable ...


Lead‐Free Semiconductors: Soft Chemistry, Dimensionality Control, And Manganese‐Doping Of Germanium Halide Perovskites, Long Men, Bryan A. Rosales, Noreen E. Gentry, Sarah D. Cady, Javier Vela Mar 2019

Lead‐Free Semiconductors: Soft Chemistry, Dimensionality Control, And Manganese‐Doping Of Germanium Halide Perovskites, Long Men, Bryan A. Rosales, Noreen E. Gentry, Sarah D. Cady, Javier Vela

Chemistry Publications

Lead halide perovskites have drawn enormous interest due to their exceptional photovoltaic and optoelectronic properties. However, the toxic heavy metal lead is harmful to humans and the environment resulting in a need for strategies to replace this toxic element. Herein, we report a facile aqueous synthesis of CsGeX3 (X = I, Br) perovskite nanocrystals with size control achieved by varying the cysteammonium halide ligand concentration. We observe a variety of morphologies including pyramidal, hexagonal, and spheroidal. CsGeX3 nanocrystals undergo a lattice expansion due to partial replacement of Cs+ with larger cysteNH3+ cations into the lattice. We successfully dope Mn2+ into the ...


On The Kinetics Of The Removal Of Ligands From Films Of Colloidal Nanocrystals By Plasmas, Santosh Shaw, Tiago F. Silva, Pratyasha Mohapatra, Deyny Mendivelso-Perez, Xinchun Tian, Fabian Naab, Cleber L. Rodrigues, Emily A. Smith, Ludovico Cademartiri Jan 2019

On The Kinetics Of The Removal Of Ligands From Films Of Colloidal Nanocrystals By Plasmas, Santosh Shaw, Tiago F. Silva, Pratyasha Mohapatra, Deyny Mendivelso-Perez, Xinchun Tian, Fabian Naab, Cleber L. Rodrigues, Emily A. Smith, Ludovico Cademartiri

Ames Laboratory Accepted Manuscripts

This paper describes the kinetic limitations of etching ligands from colloidal nanocrystal assemblies (CNAs) by plasma processing. We measured the etching kinetics of ligands from a CNA model system (spherical ZrO2 nanocrystals, 2.5–3.5 nm diameter, capped with trioctylphosphine oxide) with inductively coupled plasmas (He and O2 feed gases, powers ranging from 7 to 30 W, at pressures ranging from 100 to 2000 mTorr and exposure times ranging between 6 and 168 h). The etching rate slows down by about one order of magnitude in the first minutes of etching, after which the rate of carbon removal becomes ...


Kinetics, Energetics, And Size Dependence Of The Transformation From Pt To Ordered Ptsn Intermetallic Nanoparticles, Minda Chen, Yong Han, Tian Wei Goh, Rong Sun, Raghu V. Maligal‐Ganesh, Yuchen Pei, Chia‐ Kuang Tsung, James W. Evans, Wenyu Huang Jan 2019

Kinetics, Energetics, And Size Dependence Of The Transformation From Pt To Ordered Ptsn Intermetallic Nanoparticles, Minda Chen, Yong Han, Tian Wei Goh, Rong Sun, Raghu V. Maligal‐Ganesh, Yuchen Pei, Chia‐ Kuang Tsung, James W. Evans, Wenyu Huang

Chemistry Publications

The outstanding catalytic activity and chemical selectivity of intermetallic compounds make them excellent candidates for heterogeneous catalysis. However, the kinetics of their formation at the nanoscale is poorly understood or characterized, and precise control of their size, shape as well as composition during synthesis remains challenging. Here, using well-defined Pt nanoparticles (5 nm and 14 nm) encapsulated in mesoporous silica, we study the transformation kinetics from monometallic Pt to intermetallic PtSn at different temperatures by a series of time-evolution X-ray diffraction studies. Observations indicate an initial transformation stage mediated by Pt surface-controlled intermixing kinetics, followed by a second stage with ...


Squeezed Nanocrystals: Equilibrium Configuration Of Metal Clusters Embedded Beneath The Surface Of A Layered Material, Scott E. Julien, Ann Lii-Rosales, Kai-Tak Wan, Yong Han, Michael C. Tringides, James W. Evans, Patricia A. Thiel Jan 2019

Squeezed Nanocrystals: Equilibrium Configuration Of Metal Clusters Embedded Beneath The Surface Of A Layered Material, Scott E. Julien, Ann Lii-Rosales, Kai-Tak Wan, Yong Han, Michael C. Tringides, James W. Evans, Patricia A. Thiel

Chemistry Publications

Shapes of functional metallic nanocrystals, typically synthesized either free in solution or supported on surfaces, are key for controlling properties. Here, we consider a novel new class of metallic nanocrystals, copper islands embedded near the surface of graphite, which can be considered a model system for metals embedded beneath surfaces of layered materials, or beneath supported membranes. We develop a continuum elasticity (CE) model for the equilibrium shape of these islands, and compare its predictions with experimental data. The CE model incorporates appropriate surface energy, adhesion energies, and strain energy. The agreement between the CE model and the data is ...


Reverse-Engineering Of Graphene On Metal Surfaces: A Case Study Of Embedded Ruthenium, Ann Lii-Rosales, Yong Han, Ka Man Yu, Dapeng Jing, Nathaniel Anderson, David Vaknin, Michael C. Tringides, James W. Evans, Michael S. Altman, Patricia A. Thiel Oct 2018

Reverse-Engineering Of Graphene On Metal Surfaces: A Case Study Of Embedded Ruthenium, Ann Lii-Rosales, Yong Han, Ka Man Yu, Dapeng Jing, Nathaniel Anderson, David Vaknin, Michael C. Tringides, James W. Evans, Michael S. Altman, Patricia A. Thiel

Chemistry Publications

Using scanning tunneling microscopy, x-ray photoelectron spectroscopy, and x-ray absorption spectroscopy, we show that Ru forms metallic nanoislands on graphite, covered by a graphene monolayer. These islands are air-stable, contain 2–4 layers of Ru, and have diameters on the order of 10 nm. To produce these nanoislands two conditions must be met during synthesis. The graphite surface must be ion-bombarded, and subsequently held at an elevated temperature (1000–1180 K) during Ru deposition. A coincidence lattice forms between the graphene overlayer and the Ru island top. Its characteristics—coincidence lattice constant, corrugation amplitude, and variation of carbon lattice appearance ...


Potential Of Mean Force For Two Nanocrystals: Core Geometry And Size, Hydrocarbon Unsaturation, And Universality With Respect To The Force Field, Curt Waltmann, Nathan Horst, Alex Travesset Jul 2018

Potential Of Mean Force For Two Nanocrystals: Core Geometry And Size, Hydrocarbon Unsaturation, And Universality With Respect To The Force Field, Curt Waltmann, Nathan Horst, Alex Travesset

Ames Laboratory Accepted Manuscripts

We present a detailed analysis of the interaction between two nanocrystals capped with ligands consisting of hydrocarbon chains by united atom molecular dynamics simulations. We analyze large cores (up to 10 nm in diameter) and ligands with unsaturated carbon bonds (oleic acid) and we investigate the accuracy of the computed potential of mean force by comparing different force fields. We also analyze the vortices that determine the bonding, including the case of asymmetric nanocrystals, and discuss effects related to the intrinsic anisotropy of the core. Overall our results are in agreement with the predictions of the recently proposed orbifold topological ...