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Ames Laboratory Accepted Manuscripts

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Full-Text Articles in Nanoscience and Nanotechnology

Ambient Synthesis Of Nanomaterials By In Situ Heterogeneous Metal/Ligand Reactions, Boyce S. Chang, Brijith Thomas, Jiahao Chen, Ian D. Tevis, Paul Karanja, Simge Çınar, Amrit Venkatesh, Aaron Rossini, Martin M. Thuo Jul 2019

Ambient Synthesis Of Nanomaterials By In Situ Heterogeneous Metal/Ligand Reactions, Boyce S. Chang, Brijith Thomas, Jiahao Chen, Ian D. Tevis, Paul Karanja, Simge Çınar, Amrit Venkatesh, Aaron Rossini, Martin M. Thuo

Ames Laboratory Accepted Manuscripts

Coordination polymers are ideal synthons in creating high aspect ratio nanostructures, however, conventional synthetic methods are often restricted to batch-wise and costly processes. Herein, we demonstrate a non-traditional, frugal approach to synthesize 1D coordination polymers by in situ etching of zerovalent metal particle precursors. This procedure is denoted as the heterogeneous metal/ligand reaction and was demonstrated on Group 13 metals as a proof of concept. Simple carboxylic acids supply the etchant protons and ligands for metal ions (conjugate base) in a 1 : 1 ratio. This scalable reaction produces a 1D polymer that assembles into high-aspect ratio ‘nanobeams’. We demonstrate ...


Gd5si4-Pvdf Nanocomposite Films And Their Potential For Triboelectric Energy Harvesting Applications, S. M. Harstad, P. Zhao, N. Soin, A. A. El-Gendy, Shalabh Gupta, Vitalij K. Pecharsky, J. Luo, Ravi L. Hadimani Mar 2019

Gd5si4-Pvdf Nanocomposite Films And Their Potential For Triboelectric Energy Harvesting Applications, S. M. Harstad, P. Zhao, N. Soin, A. A. El-Gendy, Shalabh Gupta, Vitalij K. Pecharsky, J. Luo, Ravi L. Hadimani

Ames Laboratory Accepted Manuscripts

The triboelectric energy generators prepared using the combination of self-polarized, high beta-phase nanocomposite films of Gd5Si4-PVDF and polyamide-6 (PA-6) films have generated significantly higher voltage of 425 V, short-circuit current density of 30 mA/m(2) and a charge density of similar to 116.7 C/m(2) as compared to corresponding values of 300 V, 30 mA/m(2) and 94.7 mu C/m(2), respectively for the pristine PVDF-(PA-6) combination. The magnetic measurements of the Gd5Si4-PVDF films display a ferromagnetic behavior as compared to diamagnetic nature of pristine PVDF. The presence of magnetic nanoparticles in the ...


Direct Observation Of Early Stages Of Growth Of Multilayered Dna-Templated Au-Pd-Au Core-Shell Nanoparticles In Liquid Phase, Nabraj Bhattarai, Tanya Prozorov Feb 2019

Direct Observation Of Early Stages Of Growth Of Multilayered Dna-Templated Au-Pd-Au Core-Shell Nanoparticles In Liquid Phase, Nabraj Bhattarai, Tanya Prozorov

Ames Laboratory Accepted Manuscripts

We report here on direct observation of early stages of formation of multilayered bimetallic Au-Pd core-shell nanocubes and Au-Pd-Au core-shell nanostars in liquid phase using low-dose in situ scanning transmission electron microscopy (S/TEM) with the continuous flow fluid cell. The reduction of Pd and formation of Au-Pd core-shell is achieved through the flow of the reducing agent. Initial rapid growth of Pd on Au along <111> direction is followed by a slower rearrangement of Pd shell. We propose the mechanism for the DNA-directed shape transformation of Au-Pd core-shell nanocubes to adopt a nanostar-like morphology in the presence of T30 DNA ...


Nonlinearity In The Dark: Broadband Terahertz Generation With Extremely High Efficiency, Ming Fang, Nian-Hai Shen, Wei E. I. Sha, Zhixiang Huang, Thomas Koschny, Costas M. Soukoulis Jan 2019

Nonlinearity In The Dark: Broadband Terahertz Generation With Extremely High Efficiency, Ming Fang, Nian-Hai Shen, Wei E. I. Sha, Zhixiang Huang, Thomas Koschny, Costas M. Soukoulis

Ames Laboratory Accepted Manuscripts

Plasmonic metamaterials and metasurfaces offer new opportunities in developing high performance terahertz emitters and detectors beyond the limitations of conventional nonlinear materials. However, simple meta-atoms for second-order nonlinear applications encounter fundamental trade-offs in the necessary symmetry breaking and local-field enhancement due to radiation damping that is inherent to the operating resonant mode and cannot be controlled separately. Here we present a novel concept that eliminates this restriction obstructing the improvement of terahertz generation efficiency in nonlinear metasurfaces based on metallic nanoresonators. This is achieved by combining a resonant dark-state metasurface, which locally drives nonlinear nanoresonators in the near field, with ...


On Loss Compensation, Amplification And Lasing In Metallic Metamaterials, Sotiris Droulias, Thomas Koschny, Maria Kafesaki, Costas M. Soukoulis Jan 2019

On Loss Compensation, Amplification And Lasing In Metallic Metamaterials, Sotiris Droulias, Thomas Koschny, Maria Kafesaki, Costas M. Soukoulis

Ames Laboratory Accepted Manuscripts

The design of metamaterials, which are artificial materials that can offer unique electromagnetic properties, is based on the excitation of strong resonant modes. Unfortunately, material absorption—mainly due to their metallic parts—can damp their resonances and hinder their operation. Incorporating a gain material can balance these losses, but this must be performed properly, as a reduced or even eliminated absorption does not guarantee loss compensation. Here we examine the possible regimes of interaction of a gain material with a passive metamaterial and show that background amplification and loss compensation are two extreme opposites, both of which can lead to ...


Growing Signals From The Noise: Challenging Nuclei In Materials Dnp, Frédéric A. Perras, Takeshi Kobayashi, Marek Pruski Sep 2018

Growing Signals From The Noise: Challenging Nuclei In Materials Dnp, Frédéric A. Perras, Takeshi Kobayashi, Marek Pruski

Ames Laboratory Accepted Manuscripts

The polarization of nuclear spins by dynamic nuclear polarization (DNP) has redefined the sensitivity limits of solid‐state (SS) NMR spectroscopy. Materials science has been arguably one of the key beneficiaries of the recent remarkable advances of the technique, which included low‐temperature magic angle spinning (MAS), modern gyrotrons, and biradical agents for polarization transfer via the cross‐effect. In many classes of materials, DNP offers the capability of selectively sensitizing progressively smaller surface and interfacial regions of materials and eliciting responses from previously undetectable nuclei, with no detrimental effect on resolution. We review the most recent applications of DNP ...


Finite-Size Effects In Metasurface Lasers Based On Resonant Dark States, Sotiris Droulias, Thomas Koschny, Costas M. Soukoulis Aug 2018

Finite-Size Effects In Metasurface Lasers Based On Resonant Dark States, Sotiris Droulias, Thomas Koschny, Costas M. Soukoulis

Ames Laboratory Accepted Manuscripts

The quest for subwavelength coherent light sources has recently led to the exploration of dark-mode based surface lasers, which allow for independent adjustment of the lasing state and its coherent radiation output. To understand how this unique design performs in real experiments, we need to consider systems of finite size and quantify finite-size effects not present in the infinite dark-mode surface laser model. Here we find that, depending on the size of the system, distinct and even counterintuitive behavior of the lasing state is possible, determined by a balanced competition between multiple loss channels, including dissipation, intentional out-coupling of coherent ...


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 ...


On Spinodal Decomposition In Alnico - A Transmission Electron Microscopy And Atom Probe Tomography Study, Lin Zhou, Wei Guo, J. D. Poplawsky, Liqin Ke, Iver E. Anderson, Matthew J. Kramer Jul 2018

On Spinodal Decomposition In Alnico - A Transmission Electron Microscopy And Atom Probe Tomography Study, Lin Zhou, Wei Guo, J. D. Poplawsky, Liqin Ke, Iver E. Anderson, Matthew J. Kramer

Ames Laboratory Accepted Manuscripts

Alnico is a prime example of a finely tuned nanostructure whose magnetic properties are intimately connected to magnetic annealing (MA) during spinodal transformation and subsequent lower temperature annealing (draw) cycles. Using a combination of transmission electron microscopy and atom probe tomography, we show how these critical processing steps affect the local composition and nanostructure evolution with impact on magnetic properties. The nearly 2-fold increase of intrinsic coercivity (Hci) during the draw cycle is not adequately explained by chemical refinement of the spinodal phases. Instead, increased Fe-Co phase (α1) isolation, development of Cu-rich spheres/rods/blades and additional α1 rod precipitation ...


Creating Metamaterial Building Blocks With Directed Photochemical Metallization Of Silver Onto Dna Origami Templates, Md Mir Hossen, Lee Bendickson, Pierre Palo, Zhiqi Yao, Marit Nilsen-Hamilton, Andrew C. Hillier Jun 2018

Creating Metamaterial Building Blocks With Directed Photochemical Metallization Of Silver Onto Dna Origami Templates, Md Mir Hossen, Lee Bendickson, Pierre Palo, Zhiqi Yao, Marit Nilsen-Hamilton, Andrew C. Hillier

Ames Laboratory Accepted Manuscripts

DNA origami can be used to create a variety of complex and geometrically unique nanostructures that can be further modified to produce building blocks for applications such as in optical metamaterials. We describe a method for creating metal-coated nanostructures using DNA origami templates and a photochemical metallization technique. Triangular DNA origami forms were fabricated and coated with a thin metal layer by photochemical silver reduction while in solution or supported on a surface. The DNA origami template serves as a localized photosensitizer to facilitate reduction of silver ions directly from solution onto the DNA surface. The metallizing process is shown ...


Two-Dimensional Crystallization Of Poly(N-Isopropylacrylamide)-Capped Gold Nanoparticles, Wenjie Wang, Jack J. Lawrence, Wei Bu, Honghu Zhang, David Vaknin Jun 2018

Two-Dimensional Crystallization Of Poly(N-Isopropylacrylamide)-Capped Gold Nanoparticles, Wenjie Wang, Jack J. Lawrence, Wei Bu, Honghu Zhang, David Vaknin

Ames Laboratory Accepted Manuscripts

Surface-sensitive X-ray reflectivity and grazing incidence small-angle X-ray scattering reveal the structure of polymer-capped-gold nanoparticles (AuNPs that are grafted with poly(N-isopropylacrylamide); PNIPAM–AuNPs) as they self-assemble and crystallize at the aqueous suspension/vapor interface. Citrate-stabilized AuNPs (5 and 10 nm in nominal diameter) are ligand-exchanged by 6 kDa PNIPAM-thiol to form corona brushes around the AuNPs that are highly stable and dispersed in aqueous suspensions. Surprisingly, no clear evidence of thermosensitive effect on surface enrichment or self-assembly of the PNIPAM–AuNPs is observed in the 10–35 °C temperature range. However, addition of simple salts (in this case ...


Tailoring Bandgap Of Perovskite Batio3 By Transition Metals Co-Doping For Visible-Light Photoelectrical Applications: A First-Principles Study, Fan Yang, Liang Yang, Changzhi Ai, Pengcheng Xie, Shiwei Lin, Cai-Zhuang Wang, Xihong Lu Jun 2018

Tailoring Bandgap Of Perovskite Batio3 By Transition Metals Co-Doping For Visible-Light Photoelectrical Applications: A First-Principles Study, Fan Yang, Liang Yang, Changzhi Ai, Pengcheng Xie, Shiwei Lin, Cai-Zhuang Wang, Xihong Lu

Ames Laboratory Accepted Manuscripts

The physical and chemical properties of V-M″ and Nb-M″ (M″ is 3d or 4d transition metal) co-doped BaTiO3were studied by first-principles calculation based on density functional theory. Our calculation results show that V-M″ co-doping is more favorable than Nb-M″ co-doping in terms of narrowing the bandgap and increasing the visible-light absorption. In pure BaTiO3, the bandgap depends on the energy levels of the Ti 3d and O 2p states. The appropriate co-doping can effectively manipulate the bandgap by introducing new energy levels interacting with those of the pure BaTiO3. The optimal co-doping effect comes from the ...


Many Body Effects And Icosahedral Order In Superlattice Self-Assembly, Tommy Waltmann, Curt Waltmann, Nathan Horst, Alex Travesset Jun 2018

Many Body Effects And Icosahedral Order In Superlattice Self-Assembly, Tommy Waltmann, Curt Waltmann, Nathan Horst, Alex Travesset

Ames Laboratory Accepted Manuscripts

We elucidate how nanocrystals “bond” to form ordered structures. For that purpose we consider nanocrystal configurations consisting of regular polygons and polyhedra, which are the motifs that constitute single component and binary nanocrystal superlattices, and simulate them using united atom models. We compute the free energy and quantify many body effects, i.e., those that cannot be accounted for by pair potential (two-body) interactions, further showing that they arise from coalescing vortices of capping ligands. We find that such vortex textures exist for configurations with local coordination number ≤6. For higher coordination numbers, vortices are expelled and nanocrystals arrange in ...


Probing Magnetism In 2d Van Der Waals Crystalline Insulators Via Electron Tunneling, D. R. Klein, D. Macneill, J. L. Lado, D. Soriano, E. Navarro-Moratalla, K. Watanabe, T. Taniguchi, S. Manni, Paul C. Canfield, J. Fernández-Rossier, P. Jarillo-Herrero Jun 2018

Probing Magnetism In 2d Van Der Waals Crystalline Insulators Via Electron Tunneling, D. R. Klein, D. Macneill, J. L. Lado, D. Soriano, E. Navarro-Moratalla, K. Watanabe, T. Taniguchi, S. Manni, Paul C. Canfield, J. Fernández-Rossier, P. Jarillo-Herrero

Ames Laboratory Accepted Manuscripts

Magnetic insulators are a key resource for next-generation spintronic and topological devices. The family of layered metal halides promises varied magnetic states, including ultrathin insulating multiferroics, spin liquids, and ferromagnets, but device-oriented characterization methods are needed to unlock their potential. Here, we report tunneling through the layered magnetic insulator CrI3 as a function of temperature and applied magnetic field. We electrically detect the magnetic ground state and interlayer coupling and observe a field-induced metamagnetic transition. The metamagnetic transition results in magnetoresistances of 95, 300, and 550% for bilayer, trilayer, and tetralayer CrI3 barriers, respectively. We further measure inelastic tunneling spectra ...


Solute Effects On Interfacial Dislocation Emission In Nanomaterials: Nucleation Site Competition And Neutralization, Valery Borovikov, Mikhail I. Mendelev, Alexander H. King May 2018

Solute Effects On Interfacial Dislocation Emission In Nanomaterials: Nucleation Site Competition And Neutralization, Valery Borovikov, Mikhail I. Mendelev, Alexander H. King

Ames Laboratory Accepted Manuscripts

Solutes added to stabilize nano-crystalline metals against grain growth, may segregate to grain boundaries and triple junctions where they can affect the process of the dislocation emission. We demonstrate that this effect can be very complex due to different rates of segregation at different interfaces. Moreover, at large concentrations, when the solutes form clusters, the interfaces between these clusters and the matrix can introduce new dislocation emission sources, which can be activated under lower applied stress. Thus, the strength maximum can occur at a certain solute concentration: adding solutes beyond this optimal concentration can reduce the strength of the material.


Large-Scale Synthesis Of Colloidal Si Nanocrystals And Their Helium Plasma Processing Into Spin-On, Carbon-Free Nanocrystalline Si Films, Pratyasha Mohapatra, Deyny Mendivelso-Perez, Jonathan M. Bobbitt, Santosh Shaw, Bin Yuan, Xinchun Tian, Emily A. Smith, Ludovico Cademartiri May 2018

Large-Scale Synthesis Of Colloidal Si Nanocrystals And Their Helium Plasma Processing Into Spin-On, Carbon-Free Nanocrystalline Si Films, Pratyasha Mohapatra, Deyny Mendivelso-Perez, Jonathan M. Bobbitt, Santosh Shaw, Bin Yuan, Xinchun Tian, Emily A. Smith, Ludovico Cademartiri

Ames Laboratory Accepted Manuscripts

This paper describes a simple approach to the large-scale synthesis of colloidal Si nanocrystals and their processing into spin-on carbon-free nanocrystalline Si films. The synthesized silicon nanoparticles are capped with decene, dispersed in hexane, and deposited on silicon substrates. The deposited films are exposed to nonoxidizing room-temperature He plasma to remove the organic ligands without adversely affecting the silicon nanoparticles to form crack-free thin films. We further show that the reactive ion etching rate in these films is 1.87 times faster than that for single-crystalline Si, consistent with a simple geometric argument that accounts for the nanoscale roughness caused ...


The Crystal Facet-Dependent Electrochemical Performance Of Tio2 Nanocrystals For Heavy Metal Detection: Theoretical Prediction And Experimental Proof, Jianjun Liao, Fan Yang, Cai-Zhuang Wang, Shiwei Lin May 2018

The Crystal Facet-Dependent Electrochemical Performance Of Tio2 Nanocrystals For Heavy Metal Detection: Theoretical Prediction And Experimental Proof, Jianjun Liao, Fan Yang, Cai-Zhuang Wang, Shiwei Lin

Ames Laboratory Accepted Manuscripts

Tailored design/fabrication of electroanalytical materials with highly-active exposed crystal planes is of great importance for the development of electrochemical sensing. In this work, combining experimental and theoretical efforts, we reported a facile strategy to fabricate TiO2 nanocrystals with tunable electrochemical performance for heavy metal detection. Density functional theory (DFT) calculations indicated that TiO2 (001) facet showed relative larger adsorption energy and lower diffusion energy barrier toward heavy metal ions, which is favorable for obtaining better electrochemical stripping behaviors. Based on this prediction, a series of TiO2 nanocrystals with different ratios of exposed (001) and (101) facets were synthesized. Electrochemical ...


Investigating Phase Transition Temperatures Of Size Separated Gadolinium Silicide Magnetic Nanoparticles, Shivakumar G. Hunagund, Shane M. Harstad, Ahmed A. El-Gendy, Shalbh Gupta, Vitalij K. Pecharsky, Ravi L. Hadimani May 2018

Investigating Phase Transition Temperatures Of Size Separated Gadolinium Silicide Magnetic Nanoparticles, Shivakumar G. Hunagund, Shane M. Harstad, Ahmed A. El-Gendy, Shalbh Gupta, Vitalij K. Pecharsky, Ravi L. Hadimani

Ames Laboratory Accepted Manuscripts

Gadolinium silicide (Gd5Si4) nanoparticles (NPs) exhibit different properties compared to their parent bulk materials due to finite size, shape, and surface effects. NPs were prepared by high energy ball-milling of the as-cast Gd5Si4ingot and size separated into eight fractions using time sensitive sedimentation in an applied dc magnetic field with average particle sizes ranging from 700 nm to 82 nm. The largest Gd5Si4 NPs order ferromagnetically at 316 K. A second anomaly observed at 110 K can be ascribed to a Gd5Si3 impurity. As the particle sizes decrease, the volume fraction of Gd5Si3 phase increases at the expense of the ...


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 Mar 2018

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

Ames Laboratory Accepted Manuscripts

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.


Replica Molding-Based Nanopatterning Of Tribocharge On Elastomer With Application To Electrohydrodynamic Nanolithography, Qiang Li, Akshit Peer, In-Ho Cho, Rana Biswas, Jaeyoun Kim Mar 2018

Replica Molding-Based Nanopatterning Of Tribocharge On Elastomer With Application To Electrohydrodynamic Nanolithography, Qiang Li, Akshit Peer, In-Ho Cho, Rana Biswas, Jaeyoun Kim

Ames Laboratory Accepted Manuscripts

Replica molding often induces tribocharge on elastomers. To date, this phenomenon has been studied only on untextured elastomer surfaces even though replica molding is an effective method for their nanotexturing. Here we show that on elastomer surfaces nanotextured through replica molding the induced tribocharge also becomes patterned at nanoscale in close correlation with the nanotexture. By applying Kelvin probe microscopy, electrohydrodynamic lithography, and electrostatic analysis to our model nanostructure, poly(dimethylsiloxane) nanocup arrays replicated from a polycarbonate nanocone array, we reveal that the induced tribocharge is highly localized within the nanocup, especially around its rim. Through finite element analysis, we ...


Unveiling The Effects Of Linker Substitution In Suzuki Coupling With Palladium Nanoparticles In Metal–Organic Frameworks, Xinle Li, Biying Zhang, Ryan Van Zeeland, Linlin Tang, Yuchen Pei, Tian Wei Goh, Levi M. Stanley, Wenyu Huang Mar 2018

Unveiling The Effects Of Linker Substitution In Suzuki Coupling With Palladium Nanoparticles In Metal–Organic Frameworks, Xinle Li, Biying Zhang, Ryan Van Zeeland, Linlin Tang, Yuchen Pei, Tian Wei Goh, Levi M. Stanley, Wenyu Huang

Ames Laboratory Accepted Manuscripts

The establishment of structure–property relationships in heterogeneous catalysis is of prime importance but remains a formidable challenge. Metal–organic frameworks (MOFs) featuring excellent chemical tunability are emerging as an auspicious platform for the atomic-level control of heterogeneous catalysis. Herein, we encapsulate palladium nanoparticles (Pd NPs) in a series of isoreticular mixed-linker MOFs, and the obtained MOF-Pd NPs catalysts were used to unveil the electronic and steric effects of linker substitution on the activity of these catalysts in the Suzuki–Miyaura cross-coupling reactions. Significantly, m-6,6′-Me2bpy-MOF-Pd exhibits a remarkable enhancement in the activity compared to non-functionalized m-bpy-MOF-Pd and m-4 ...


Development Of A Semigraphitic Sulfur-Doped Ordered Mesoporous Carbon Material For Electroanalytical Applications, Jaqueline R. Maluta, Sergio A.S. Machado, Umesh Chaudhary, J. Sebastian Manzano, Lauro T. Kubota, Igor I. Slowing Mar 2018

Development Of A Semigraphitic Sulfur-Doped Ordered Mesoporous Carbon Material For Electroanalytical Applications, Jaqueline R. Maluta, Sergio A.S. Machado, Umesh Chaudhary, J. Sebastian Manzano, Lauro T. Kubota, Igor I. Slowing

Ames Laboratory Accepted Manuscripts

The modification of traditional electrodes with mesoporous carbons is a promising strategy to produce high performance electrodes for electrochemical sensing. The high surface area of mesoporous carbons provides a large number of electroactive sites for binding analytes. Controlling the pore size and structure of mesoporous carbons and modifying their electronic properties via doping offers additional benefits like maximizing transport and tuning the electrochemical processes associated with analyte detection. This work reports a facile method to produce sulfur-doped ordered mesoporous carbon materials (S-OMC) with uniform pore structure, large pore volume, high surface area and semigraphitic structure. The synthesis used thiophenol as ...


Mechanochemistry Of The Libh4–Alcl3 System: Structural Characterization Of The Products By Solid-State Nmr, Takeshi Kobayashi, Oleksandr Dolotko, Shalbh Gupta, Vitalij K. Pecharsky, Marek Pruski Feb 2018

Mechanochemistry Of The Libh4–Alcl3 System: Structural Characterization Of The Products By Solid-State Nmr, Takeshi Kobayashi, Oleksandr Dolotko, Shalbh Gupta, Vitalij K. Pecharsky, Marek Pruski

Ames Laboratory Accepted Manuscripts

The double-cation metal borohydride, Li4Al3(BH4)(13), mechanochemically produced from a 13:3 mixture of lithium borohydride (LiBH4) and aluminum chloride (AlCl3), has a low hydrogen desorption temperature; however, the material's decomposition is accompanied by a large emission of toxic diborane (B2H6). We found that a decrease of the LiBH4:AICl(3) ratio in the starting mixture yields increased amounts of partially chlorinated products that also dehydrogenate at low temperature, but release negligibly small amounts of diborane. Extensive characterization by solid-state NMR spectroscopy (SSNMR) and powder X-ray diffraction (XRD) found that the 11:3 ratio product maintains the Li ...


High-Performance Flexible All-Solid-State Asymmetric Supercapacitors Based On Vertically Aligned Cuse@Co(Oh)2 Nanosheet Arrays, Jiangfeng Gong, Yazhou Tian, Ziyuan Yang, Qianjin Wang, Xihao Hong, Qing-Ping Ding Feb 2018

High-Performance Flexible All-Solid-State Asymmetric Supercapacitors Based On Vertically Aligned Cuse@Co(Oh)2 Nanosheet Arrays, Jiangfeng Gong, Yazhou Tian, Ziyuan Yang, Qianjin Wang, Xihao Hong, Qing-Ping Ding

Ames Laboratory Accepted Manuscripts

The developments of electrode active materials provide the opportunities for next-generation energy storage devices. The arrangement of electrode materials on the substrate has recently emerged as a promising strategy for preparing high-performance supercapacitors. Herein, we demonstrate a novel vertically aligned CuSe@Co(OH)(2) nanosheet arrays electrode for supercapacitor application. The materials are thoroughly characterized by structural and spectroscopic techniques. Electrochemical performance of CuSe@Co(OH)(2) nanosheet arrays are investigated in detail, which exhibit a specific capacitance as much as 1180 F g(-1) at a current density of 1 A g(-1). A flexible asymmetric all-solid-state supercapacitor is ...


Diffusion Of Two-Dimensional Epitaxial Clusters On Metal (100) Surfaces: Facile Versus Nucleation-Mediated Behavior And Their Merging For Larger Sizes, King C. Lai, Da-Jiang Liu, James W. Evans Dec 2017

Diffusion Of Two-Dimensional Epitaxial Clusters On Metal (100) Surfaces: Facile Versus Nucleation-Mediated Behavior And Their Merging For Larger Sizes, King C. Lai, Da-Jiang Liu, James W. Evans

Ames Laboratory Accepted Manuscripts

For diffusion of two-dimensional homoepitaxial clusters of N atoms on metal (100) surfaces mediated by edge atom hopping, macroscale continuum theory suggests that the diffusion coefficient scales like DN∼N−β with β=3/2. However, we find quite different and diverse behavior in multiple size regimes. These include: (i) facile diffusion for small sizes N<9; (ii) slow nucleation-mediated diffusion with small β<1 for “perfect” sizes N=Np=L2 or L(L+1), for L=3,4, ... having unique ground-state shapes, for moderate sizes 9≤N≤O(102); the same also applies for N=Np+3, Np+4, ...(iii) facile diffusion but with large β>2 for N=Np+1 and Np+2 also for moderate sizes 9≤N≤O(102); (iv) merging of the above distinct branches and subsequent anomalous scaling with 1≲β<3/2, reflecting the quasifacetted structure of clusters, for larger N=O(102) to N=O(103); (v) classic scaling with β=3/2 for very large N=O(103) and above. The specified size ranges apply for typical model parameters. We focus on the moderate size regime where we show that diffusivity cycles quasiperiodically from the slowest branch for Np+3 (not Np) to the fastest branch for Np+1. Behavior is quantified by kinetic Monte Carlo simulation of an appropriate stochastic lattice-gas model. However, precise analysis must account for a strong enhancement of diffusivity for short time increments due to back correlation in the cluster motion. Further understanding of this enhancement, of anomalous size scaling behavior, and of the merging of various branches, is facilitated by combinatorial analysis of the number of the ground-state and low-lying excited state cluster configurations, and also of kink populations.


Ionic Depletion At The Crystalline Gibbs Layer Of Peg-Capped Gold Nanoparticle Brushes At Aqueous Surfaces, Wenjie Wang, Honghu Zhang, Surya Mallapragada, Alex Travesset, David Vaknin Dec 2017

Ionic Depletion At The Crystalline Gibbs Layer Of Peg-Capped Gold Nanoparticle Brushes At Aqueous Surfaces, Wenjie Wang, Honghu Zhang, Surya Mallapragada, Alex Travesset, David Vaknin

Ames Laboratory Accepted Manuscripts

In situ surface-sensitive x-ray diffraction and grazing incidence x-ray fluorescence spectroscopy (GIXFS) methods are combined to determine the ionic distributions across the liquid/vapor interfaces of thiolated-polyethylene-glycol–capped gold nanoparticle (PEG-AuNP) solutions. Induced by the addition of salts (i.e., Cs2SO4) to PEG-AuNPs solutions, two-dimensional hexagonal lattices of PEG-AuNPs form spontaneously at the aqueous surfaces, as is demonstrated by x-ray reflectivity and grazing incidence small-angle x-ray scattering. By taking advantage of element specificity with the GIXFS method, we find that the cation Cs+ concentration at the crystalline film is significantly reduced in parts of the PEG-AuNP film compared with that ...


Calcination Does Not Remove All Carbon From Colloidal Nanocrystal Assemblies, Pratyasha Mohapatra, Santosh Shaw, Deyny Mendivelso-Perez, Jonathan M. Bobbitt, Tiago F. Silva, Fabian Naab, Bin Yuan, Xinchun Tian, Emily A. Smith, Ludovico Cademartiri Dec 2017

Calcination Does Not Remove All Carbon From Colloidal Nanocrystal Assemblies, Pratyasha Mohapatra, Santosh Shaw, Deyny Mendivelso-Perez, Jonathan M. Bobbitt, Tiago F. Silva, Fabian Naab, Bin Yuan, Xinchun Tian, Emily A. Smith, Ludovico Cademartiri

Ames Laboratory Accepted Manuscripts

Removing organics from hybrid nanostructures is a crucial step in many bottom-up materials fabrication approaches. It is usually assumed that calcination is an effective solution to this problem, especially for thin films. This assumption has led to its application in thousands of papers. We here show that this general assumption is incorrect by using a relevant and highly controlled model system consisting of thin films of ligand-capped ZrO2 nanocrystals. After calcination at 800 °C for 12 h, while Raman spectroscopy fails to detect the ligands after calcination, elastic backscattering spectrometry characterization demonstrates that ~18% of the original carbon atoms are ...


Optical Absorption Properties Of Ge2–44 And P-Doped Ge Nanoparticles, Wei Qin, Wen-Cai Lu, Li-Zhen Zhao, Kai-Ming Ho, Cai-Zhuang Wang Dec 2017

Optical Absorption Properties Of Ge2–44 And P-Doped Ge Nanoparticles, Wei Qin, Wen-Cai Lu, Li-Zhen Zhao, Kai-Ming Ho, Cai-Zhuang Wang

Ames Laboratory Accepted Manuscripts

The optical absorption properties of non-crystalline and crystalline Ge nanoparticles with the sizes from ∼2.5 to 15 Å have been studied at the B3LYP/6-31G level using time-dependent density functional theory. Hydrogen passivation and phosphorus doping on some selected Ge nanoparticles were also calculated. With the increase of cluster size, the optical absorption spectra of the non-crystalline Ge nanoparticles change from many peaks to a continuous broad band and at the same time exhibit a systematic red-shift. Doping phosphorus also causes the absorption spectra to shift toward the lower energy region for both non-crystalline and crystalline Ge nanoparticles. The ...


Vertically-Aligned Mn(Oh)2 Nanosheet Films For Flexible All-Solid-State Electrochemical Supercapacitors, Ziyuan Yang, Jiangfeng Gong, Chunmei Tang, Weihua Zhu, Zhaojun Cheng, Jinghua Jiang, Aibin Ma, Qingping Ding Dec 2017

Vertically-Aligned Mn(Oh)2 Nanosheet Films For Flexible All-Solid-State Electrochemical Supercapacitors, Ziyuan Yang, Jiangfeng Gong, Chunmei Tang, Weihua Zhu, Zhaojun Cheng, Jinghua Jiang, Aibin Ma, Qingping Ding

Ames Laboratory Accepted Manuscripts

The arrangement of the electrode materials is a significant contributor for constructing high performance supercapacitor. Here, vertically-aligned Mn(OH)2 nanosheet thin films were synthesized by cathodic electrodeposition technique on flexible Au coated polyethylene terephthalate substrates. Morphologies, microstructures, chemical compositions and valence state of the nanosheet films were characterized systematically. It shows that the nanosheets arranged vertically to the substrate, forming a porous nanowall structures and creating large open framework, which greatly facilitate the adsorption or diffusion of electrolyte ions for faradaic redox reaction. Electrochemical tests of the films show the specific capacitance as high as 240.2 F g ...


Communication: Diverse Nanoscale Cluster Dynamics: Diffusion Of 2d Epitaxial Clusters, King C. Lai, James W. Evans, Da-Jiang Liu Nov 2017

Communication: Diverse Nanoscale Cluster Dynamics: Diffusion Of 2d Epitaxial Clusters, King C. Lai, James W. Evans, Da-Jiang Liu

Ames Laboratory Accepted Manuscripts

The dynamics of nanoscale clusters can be distinct from macroscale behavior described by continuum formalisms. For diffusion of 2D clusters of N atoms in homoepitaxial systems mediated by edge atom hopping, macroscale theory predicts simple monotonic size scaling of the diffusion coefficient, DN ∼ N−β, with β = 3/2. However, modeling for nanoclusters on metal(100) surfaces reveals that slow nucleation-mediated diffusion displaying weak size scaling β < 1 occurs for “perfect” sizes Np = L2 and L(L+1) for integer L = 3,4,… (with unique square or near-square ground state shapes), and also for Np+3, Np+4,…. In contrast, fast facile nucleation-free diffusion displaying strong size scaling β ≈ 2.5 occurs for sizes Np+1 and Np+2. DN versus N oscillates strongly between the slowest branch (for Np+3) and the fastest branch (for Np+1). All branches merge for N = O(102), but macroscale behavior is only achieved for much larger N = O(103). This analysis reveals the unprecedented diversity of behavior on the nanoscale.