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A Simple Two-Dimensional Model System To Study Electrostatic-Self-Assembly, Rebecca Cademartiri
A Simple Two-Dimensional Model System To Study Electrostatic-Self-Assembly, Rebecca Cademartiri
Rebecca Cademartiri
This paper surveys the variables controlling the lattice structure and charge in macroscopic Coulombic crystals made from electrically charged, millimeter-sized polymer objects (spheres, cubes, and cylinders). Mechanical agitation of these objects inside planar, bounded containers caused them to charge electrically through contact electrification, and to self-assemble. The processes of electrification and self-assembly, and the characteristics of the assemblies, depended on the type of motion used for agitation, on the type of materials used for the objects and the dish, on the size and shape of the objects and the dish, and on the number of objects. Each of the three …
Time-Resolved Resonance Raman And Computational Investigation Of The Influence Of 4-Acetamido And 4-N-Methylacetamido Substituents On The Chemistry Of Phenylnitrene, Jiaden Xue, Shubham Vyas, Yong Du, Hoi-Ling Luk, Yung-Ping Chuang, Tracy Yuen Sze But, Patrick H. Toy, Jin Wang, Arthur Winter, David Lee Phillips, Christopher M. Hadad, Matthew S. Platz
Time-Resolved Resonance Raman And Computational Investigation Of The Influence Of 4-Acetamido And 4-N-Methylacetamido Substituents On The Chemistry Of Phenylnitrene, Jiaden Xue, Shubham Vyas, Yong Du, Hoi-Ling Luk, Yung-Ping Chuang, Tracy Yuen Sze But, Patrick H. Toy, Jin Wang, Arthur Winter, David Lee Phillips, Christopher M. Hadad, Matthew S. Platz
Arthur Winter
A time-resolved resonance Raman (TR3) and computational investigation of the photochemistry of 4-acetamidophenyl azide and 4-N-methylacetamidophenyl azide in acetonitrile is presented. Photolysis of 4-acetamidophenyl azide appears to initially produce singlet 4-acetamidophenylnitrene which undergoes fast intersystem crossing (ISC) to form triplet 4-acetamidophenylnitrene. The latter species formally produces 4,4′-bisacetamidoazobenzene. RI-CC2/TZVP and TD-B3LYP/TZVP calculations predict the formation of the singlet nitrene from the photogenerated S1 surface of the azide excited state. The triplet 4-acetamidophenylnitrene and 4,4′-bisacetamidoazobenzene species are both clearly observed on the nanosecond to microsecond time-scale in TR3 experiments. In contrast, only one species can be observed in analogous TR3 experiments after …
Rh1−Xpdxnanoparticle Composition Dependence In Co Oxidation By Oxygen: Catalytic Activity Enhancement In Bimetallic Systems, James Russell Renzas, Wenyu Huang, Yawen Zhang, Michael E. Grass, Dat Tien Hoang, Selim Alayoglu, Derek R. Butcher, Franklin Tao, Zhi Liu, Gabor A. Somorjai
Rh1−Xpdxnanoparticle Composition Dependence In Co Oxidation By Oxygen: Catalytic Activity Enhancement In Bimetallic Systems, James Russell Renzas, Wenyu Huang, Yawen Zhang, Michael E. Grass, Dat Tien Hoang, Selim Alayoglu, Derek R. Butcher, Franklin Tao, Zhi Liu, Gabor A. Somorjai
Wenyu Huang
Bimetallic 15 nm Rh1−xPdxnanoparticle catalysts of five different compositions and supported on Si wafers have been synthesized, characterized using TEM, SEM, and XPS, and studied in CO oxidation by O2 in two pressure regimes: atmospheric pressure and 100–200 mTorr. The RhPd bimetallic nanocrystals exhibited similar synergetic effect of increased reaction activity at both atmospheric (760 Torr) and moderate (100–200 mTorr) pressures compared with pure Pd or Rh. The magnitude of the effect depends on the relative pressures of the CO and O2 reactant gases and the reaction temperature. The catalytic activity of the nanocrystals measured at moderate pressure is directly …
2-(3,5-Dinitrophenyl)-1,3-Dithiane Carbanion: A Benzylic Anion With A Low Energy Triplet State, Raffaele R. Perrotta, Arthur Winter, William H. Coldren, Daniel E. Falvey
2-(3,5-Dinitrophenyl)-1,3-Dithiane Carbanion: A Benzylic Anion With A Low Energy Triplet State, Raffaele R. Perrotta, Arthur Winter, William H. Coldren, Daniel E. Falvey
Arthur Winter
Calculations at the DFT level predict that benzyl anions with strong π-electron-withdrawing groups in the meta position(s) have low energy diradical or triplet electronic states. Specifically, the 2-(3,5-dinitrophenyl)-1,3-dithiane carbanion is predicted to have nearly degenerate singlet and triplet states at the (U)B3LYP level as a free anion. Its lithium ion pair is predicted to be a ground-state triplet with a substantial (26 kcal/mol) singlet–triplet energy gap. Experiments on this anion using chemical trapping, NMR, and the Evans method strongly suggest that this anion is either a triplet or a ground-state singlet with a very low energy triplet state.
A Pt-Cluster-Based Heterogeneous Catalyst For Homogeneous Catalytic Reactions: X-Ray Absorption Spectroscopy And Reaction Kinetic Studies Of Their Activity And Stability Against Leaching, Yimin Li, Jack Hung Chang Liu, Cole A. Witham, Wenyu Huang, Matthew A. Marcus, Sirine C. Fakra, Pinar Alayoglu, Zhongwei Zhu, Christopher M. Thompson, Arpana Arjun, Kihong Lee, Elad Gross, F. Dean Toste, Gabor A. Somorjai
A Pt-Cluster-Based Heterogeneous Catalyst For Homogeneous Catalytic Reactions: X-Ray Absorption Spectroscopy And Reaction Kinetic Studies Of Their Activity And Stability Against Leaching, Yimin Li, Jack Hung Chang Liu, Cole A. Witham, Wenyu Huang, Matthew A. Marcus, Sirine C. Fakra, Pinar Alayoglu, Zhongwei Zhu, Christopher M. Thompson, Arpana Arjun, Kihong Lee, Elad Gross, F. Dean Toste, Gabor A. Somorjai
Wenyu Huang
The design and development of metal-cluster-based heterogeneous catalysts with high activity, selectivity, and stability under solution-phase reaction conditions will enable their applications as recyclable catalysts in large-scale fine chemicals production. To achieve these required catalytic properties, a heterogeneous catalyst must contain specific catalytically active species in high concentration, and the active species must be stabilized on a solid catalyst support under solution-phase reaction conditions. These requirements pose a great challenge for catalysis research to design metal-cluster-based catalysts for solution-phase catalytic processes. Here, we focus on a silica-supported, polymer-encapsulated Pt catalyst for an electrophilic hydroalkoxylation reaction in toluene, which exhibits superior …
Spectroscopic Study Of Platinum And Rhodium Dendrimer (Pamam G4oh) Compounds: Structure And Stability, Yuri Borodko, Christopher M. Thompson, Wenyu Huang, Huseyin B. Yildiz, Heinz Frei, Gabor A. Somorjai
Spectroscopic Study Of Platinum And Rhodium Dendrimer (Pamam G4oh) Compounds: Structure And Stability, Yuri Borodko, Christopher M. Thompson, Wenyu Huang, Huseyin B. Yildiz, Heinz Frei, Gabor A. Somorjai
Wenyu Huang
Hydroxyl-terminated, poly(amidoamine) (PAMAM) dendrimer-capped platinum and rhodium nanoparticles were studied with UV−vis, Fourier transform IR, and UV-Raman spectroscopy. The adsorption bands in the region of 190−900 nm were shown to be sensitive to the electronic structure of Pt compounds in solution and in the solid state. The electron charge-transfer Pt2+ ← N band at 260 nm was attributed to mononuclear Pt2+ compounds, and resonance Raman (244 nm) established that the electron donors are amide nitrogen atoms. Multidentate coordination bonding with Pt2+ causes a strong stabilizing chelate effect, and this entropic factor hinders reduction of Pt2+ by BH4−. UV diffuse-reflectance spectra …
Rh1−X Pd X Nanoparticle Composition Dependence In Co Oxidation By No, James Russell Renzas, Wenyu Huang, Yawen Zhang, Michael E. Grass, Gabor A. Somorjai
Rh1−X Pd X Nanoparticle Composition Dependence In Co Oxidation By No, James Russell Renzas, Wenyu Huang, Yawen Zhang, Michael E. Grass, Gabor A. Somorjai
Wenyu Huang
Bimetallic 15 nm Pd-core Rh-shell Rh1−x Pd x nanoparticle catalysts have been synthesized and studied in CO oxidation by NO. The catalysts exhibited composition-dependent activity enhancement (synergy) in CO oxidation in high NO pressures. The observed synergetic effect is attributed to the favorable adsorption of CO on Pd in NO-rich conditions. The Pd-rich bimetallic catalysts deactivated after many hours of oxidation of CO by NO. After catalyst deactivation, product formation was proportional to the Rh molar fraction within the bimetallic nanoparticles. The deactivated catalysts were regenerated by heating the sample in UHV. This regeneration suggests that the deactivation was caused …
Photochemical Heterolysis Of 3,5-Bis(Dimethylamino)Benzyl Alcohols And Esters: Generation Of A Benzyl Cation With A Low-Energy Triplet State, Raffaele R. Perrotta, Arthur Winter, Daniel E. Falvey
Photochemical Heterolysis Of 3,5-Bis(Dimethylamino)Benzyl Alcohols And Esters: Generation Of A Benzyl Cation With A Low-Energy Triplet State, Raffaele R. Perrotta, Arthur Winter, Daniel E. Falvey
Arthur Winter
An earlier computational study (CASPT2/pVDZ) by Winter et al. predicts the 3,5-bis(dimethylamino)benzyl cation to have nearly degenerate singlet and triplet states. Through product studies it is demonstrated that photolysis of 3,5-bis(dimethylamino)benzyl alcohol and its corresponding acetate and phenylacetate esters in alcoholic solvents produces a solvent incorporated adduct, 3,5-bis(dimethylamino)benzyl ethers, and 3,5-bis(dimethylamino)toluene.
Vinyl Cations Substituted With Β Π-Donors Have Triplet Ground States, Arthur Winter, Daniel E. Falvey
Vinyl Cations Substituted With Β Π-Donors Have Triplet Ground States, Arthur Winter, Daniel E. Falvey
Arthur Winter
Computations at the CASPT2, CBS-QB3, and B3LYP levels of theory demonstrate that β-substitution of vinyl cations with π-donors switches the ground state of these ions from the familiar closed-shell singlet state to a carbene-like triplet state similar to the electronic state of triplet phenyl cations. Although the parent vinyl cation is a ground-state singlet species with a very large energy gap to the lowest energy triplet state, substituting the β hydrogens with just one strong π-donor (e.g., NH2, NMe2, OMe) or two moderate π-donors (e.g., F, OH, Ar, vinyl) makes the triplet state the computed ground electronic state. In many …
Size Effect Of Ruthenium Nanoparticles In Catalytic Carbon Monoxide Oxidation, Sang Hoon Joo, Jeong Y. Park, J. Russell Renzas, Derek R. Butcher, Wenyu Huang, Gabor A. Somorjai
Size Effect Of Ruthenium Nanoparticles In Catalytic Carbon Monoxide Oxidation, Sang Hoon Joo, Jeong Y. Park, J. Russell Renzas, Derek R. Butcher, Wenyu Huang, Gabor A. Somorjai
Wenyu Huang
Carbon monoxide oxidation over ruthenium catalysts has shown an unusual catalytic behavior. Here we report a particle size effect on CO oxidation over Ru nanoparticle (NP) catalysts. Uniform Ru NPs with a tunable particle size from 2 to 6 nm were synthesized by a polyol reduction of Ru(acac)3 precursor in the presence of poly(vinylpyrrolidone) stabilizer. The measurement of catalytic activity of CO oxidation over two-dimensional Ru NPs arrays under oxidizing reaction conditions (40 Torr CO and 100 Torr O2) showed an activity dependence on the Ru NP size. The CO oxidation activity increases with NP size, and the 6 nm …
Highly Active Heterogeneous Palladium Nanoparticle Catalysts For Homogeneous Electrophilic Reactions In Solution And The Utilization Of A Continuous Flow Reactor, Wenyu Huang, Jack Hung Chang Liu, Pinar Alayoglu, Yimin Li, Cole A. Whitman, Chia-Kuang Tsung, F. Dean Toste, Gabor A/ Somorjai
Highly Active Heterogeneous Palladium Nanoparticle Catalysts For Homogeneous Electrophilic Reactions In Solution And The Utilization Of A Continuous Flow Reactor, Wenyu Huang, Jack Hung Chang Liu, Pinar Alayoglu, Yimin Li, Cole A. Whitman, Chia-Kuang Tsung, F. Dean Toste, Gabor A/ Somorjai
Wenyu Huang
highly active heterogeneous Pd-nanoparticle catalyst for the intramolecular addition of phenols to alkynes was developed and employed in a continuous flow reaction system. Running the reaction in flow mode revealed reaction kinetics, such as the activation energy and catalyst deactivation, and provides many potential practical advantages.
Seedless Polyol Synthesis And Co Oxidation Activity Of Monodisperse (111)- And (100)-Oriented Rhodium Nanocrystals In Sub-10 Nm Sizes, Yawen Zhang, Michael E. Grass, Wenyu Huang, Gabor A. Somoraji
Seedless Polyol Synthesis And Co Oxidation Activity Of Monodisperse (111)- And (100)-Oriented Rhodium Nanocrystals In Sub-10 Nm Sizes, Yawen Zhang, Michael E. Grass, Wenyu Huang, Gabor A. Somoraji
Wenyu Huang
Monodisperse sub-10 nm (6.5 nm) sized Rh nanocrystals with (111) and (100) surface structures were synthesized by a seedless polyol reduction in ethylene glycol, with poly(vinylpyrrolidone) as a capping ligand. When using [Rh(Ac)2]2 as the metal precursor, (111)-oriented Rh nanopolyhedra containing 76% (111)-twinned hexagons (in 2D projection) were obtained; whereas, when employing RhCl3 as the metal precursor in the presence of alkylammonium bromide, such as tetramethylammonium bromide and trimethyl(tetradecyl)ammonium bromide, (100)-oriented Rh nanocubes were obtained with 85% selectivity. The {100} faces of the Rh nanocrystals are stabilized by chemically adsorbed Br− ions from alkylammonium bromides, which led to (100)-oriented nanocubes. …
Furan Hydrogenation Over Pt(111) And Pt(100) Single-Crystal Surfaces And Pt Nanoparticles From 1 To 7 Nm: A Kinetic And Sum Frequency Generation Vibrational Spectroscopy Study, Christopher J. Kliewer, Cesar Aliaga, Marco Bieri, Wenyu Huang, Chia-Kuang Tsung, Jennifer B. Wood, Kyriankos Komvopoulos, Gabor A. Somorjai
Furan Hydrogenation Over Pt(111) And Pt(100) Single-Crystal Surfaces And Pt Nanoparticles From 1 To 7 Nm: A Kinetic And Sum Frequency Generation Vibrational Spectroscopy Study, Christopher J. Kliewer, Cesar Aliaga, Marco Bieri, Wenyu Huang, Chia-Kuang Tsung, Jennifer B. Wood, Kyriankos Komvopoulos, Gabor A. Somorjai
Wenyu Huang
Sum frequency generation surface vibrational spectroscopy and kinetic measurements using gas chromatography have been used to systematically study the adsorption and hydrogenation of furan over Pt(111) and Pt(100) single-crystal surfaces and size-controlled 1.0-nm, 3.5-nm and 7.0-nm Pt nanoparticles at Torr pressures (10 Torr of furan, 100 Torr of H2) to form dihydrofuran, tetrahydrofuran, and the ring-cracking products butanol and propylene. As determined by SFG, the furan ring lies parallel to all Pt surfaces studied under hydrogenation conditions. Upright THF and the oxametallacycle intermediate are observed over the nanoparticle catalysts under reaction conditions. Butoxy increases in surface concentration over Pt(111) with …
Rhodium Nanoparticle Shape Dependence In The Reduction Of No By Co, James Russell Renzas, Yawen Zhang, Wenyu Huang, Gabor Somoraji
Rhodium Nanoparticle Shape Dependence In The Reduction Of No By Co, James Russell Renzas, Yawen Zhang, Wenyu Huang, Gabor Somoraji
Wenyu Huang
The shape dependence of the catalytic reduction of nitric oxide by carbon monoxide on rhodium nanopoly- hedra and nanocubes was studied from 230 to 270 ° C. The nanocubes are found to exhibit higher turnover frequency and lower activation energy than the nanopolyhedra. These trends are compared to previous studies on Rh single crystals.
Sub-10 Nm Platinum Nanocrystals With Size And Shape Control: Catalytic Study For Ethylene And Pyrrole Hydrogenation, Chia-Kuang Tsung, John N. Kuhn, Wenyu Huang, Cesar Aliaga, Ling-I Hung, Gabor A. Somorjai, Peidong Yang
Sub-10 Nm Platinum Nanocrystals With Size And Shape Control: Catalytic Study For Ethylene And Pyrrole Hydrogenation, Chia-Kuang Tsung, John N. Kuhn, Wenyu Huang, Cesar Aliaga, Ling-I Hung, Gabor A. Somorjai, Peidong Yang
Wenyu Huang
Platinum nanocubes and nanopolyhedra with tunable size from 5 to 9 nm were synthesized by controlling the reducing rate of metal precursor ions in a one-pot polyol synthesis. A two-stage process is proposed for the simultaneous control of size and shape. In the first stage, the oxidation state of the metal ion precursors determined the nucleation rate and consequently the number of nuclei. The reaction temperature controlled the shape in the second stage by regulation of the growth kinetics. These well-defined nanocrystals were loaded into MCF-17 mesoporous silica for examination of catalytic properties. Pt loadings and dispersions of the supported …
Photoaffinity Labeling Via Nitrenium Ion Chemistry: Protonation Of The Nitrene Derived From 4-Amino-3-Nitrophenyl Azide To Afford Reactive Nitrenium Ion Pairs, Valentyna Voskresenska, R. Marshall Wilson, Maxim Panov, Alexander N. Tarnovsky, Jeanette A. Krause, Shubham Vyas, Arthur Winter, Christopher M. Hadad
Photoaffinity Labeling Via Nitrenium Ion Chemistry: Protonation Of The Nitrene Derived From 4-Amino-3-Nitrophenyl Azide To Afford Reactive Nitrenium Ion Pairs, Valentyna Voskresenska, R. Marshall Wilson, Maxim Panov, Alexander N. Tarnovsky, Jeanette A. Krause, Shubham Vyas, Arthur Winter, Christopher M. Hadad
Arthur Winter
Phenyl azides with powerful electron-donating substituents are known to deviate from the usual photochemical behavior of other phenyl azides. They do not undergo ring expansion but form basic nitrenes that protonate to form nitrenium ions. The photochemistry of the widely used photoaffinity labeling system 4-amino-3-nitrophenyl azide, 5, has been studied by transient absorption spectroscopy from femtosecond to microsecond time domains and from a theoretical perspective. The nitrene generation from azide 5 occurs on the S2 surface, in violation of Kasha’s rule. The resulting nitrene is a powerful base and abstracts protons extremely rapidly from a variety of sources to form …
Self-Organized Ultrathin Oxide Nanocrystals, Ziyang Huo, Chia-Kuang Tsung, Wenyu Huang, Melissa Fardy, Ruoxue Yan, Xiaofeng Zhang, Yandong Li, Peidong Yang
Self-Organized Ultrathin Oxide Nanocrystals, Ziyang Huo, Chia-Kuang Tsung, Wenyu Huang, Melissa Fardy, Ruoxue Yan, Xiaofeng Zhang, Yandong Li, Peidong Yang
Wenyu Huang
Sub-2-nm (down to one-unit cell) uniform oxide nanocrystals and highly ordered superstructures were obtained in one step using oleylamine and oleic acid as capping and structure directing agents. The cooperative nature of the nanocrystal growth and assembly resulted in mesoscopic one-dimensional ribbon-like superstructures made of these ultrathin nanocrystals. The process reported here is general and can be readily extended to the production of many other transition metal (TiO2, ZnO, Nb2O5) and rare earth oxide (Eu2O3, Sm2O3, Er2O3, Y2O3, Tb2O3, and Yb2O3) systems.
Grain Growth And Texture Development In Lithium Fluoride Thin Films, Hakkwan Kim, Alexander H. King
Grain Growth And Texture Development In Lithium Fluoride Thin Films, Hakkwan Kim, Alexander H. King
Alexander H. King
We have studied grain-growth and texture development in polycrystalline lithium fluoride thin films using dark-field transmission electron microscopy. We demonstrate that we can isolate the size distribution of 〈111〉 surface normal grains from the overall size distribution, based on simple and plausible assumptions about the texture. The {111} texture formation and surface morphology were also observed by x-ray diffraction and atomic force microscopy, respectively. The grain-size distributions become clearly bimodal as the annealing time increases, and we deduce that the short-time size distributions are also a sum of two overlapping peaks. The smaller grain-size peak in the distribution corresponds to …
Near-Monodisperse Ni−Cu Bimetallic Nanocrystals Of Variable Composition: Controlled Synthesis And Catalytic Activity For H2 Generation, Yawen Zhang, Wenyu Huang, Susan E. Habas, John N. Kuhn, Michael E. Grass, Yusuke Yamada, Peidong Yang, Gabor A. Somorjai
Near-Monodisperse Ni−Cu Bimetallic Nanocrystals Of Variable Composition: Controlled Synthesis And Catalytic Activity For H2 Generation, Yawen Zhang, Wenyu Huang, Susan E. Habas, John N. Kuhn, Michael E. Grass, Yusuke Yamada, Peidong Yang, Gabor A. Somorjai
Wenyu Huang
Near-monodisperse Ni1−xCux (x = 0.2−0.8) bimetallic nanocrystals were synthesized by a one-pot thermolysis approach in oleylamine/1-octadecene, using metal acetylacetonates as precursors. The nanocrystals form large-area 2D superlattices, and display a catalytic synergistic effect in the hydrolysis of NaBH4 to generate H2 at x = 0.5 in a strongly basic medium. The Ni0.5Cu0.5 nanocrystals show the lowest activation energy, and also exhibit the highest H2 generation rate at 298 K.
Structure Sensitivity Of Carbon−Nitrogen Ring Opening: Impact Of Platinum Particle Size From Below 1 To 5 Nm Upon Pyrrole Hydrogenation Product Selectivity Over Monodisperse Platinum Nanoparticles Loaded Onto Mesoporous Silica, John N. Kuhn, Wenyu Huang, Chia-Kuang Tsung, Yawen Zhang, Gabor A. Somorjai
Structure Sensitivity Of Carbon−Nitrogen Ring Opening: Impact Of Platinum Particle Size From Below 1 To 5 Nm Upon Pyrrole Hydrogenation Product Selectivity Over Monodisperse Platinum Nanoparticles Loaded Onto Mesoporous Silica, John N. Kuhn, Wenyu Huang, Chia-Kuang Tsung, Yawen Zhang, Gabor A. Somorjai
Wenyu Huang
Well-defined platinum nanoparticles between 0.8 and 5.0 nm were prepared using dendrimer and polymer capping agents and supported onto mesoporous SBA-15 silica. Using these model catalysts, pyrrole hydrogenation was demonstrated to be structure sensitive because ring opening occurred more easily over larger particles compared to smaller ones. The phenomenon is caused by surface roughness or electronic effects that change with particle size.
Dendrimer Templated Synthesis Of One Nanometer Rh And Pt Particles Supported On Mesoporous Silica: Catalytic Activity For Ethylene And Pyrrole Hydrogenation, Wenyu Huang, John N. Kuhn, Chia-Kuang Tsung, Yawen Zhang, Susan E. Habas, Peidong Yang, Gabor A. Somorrjai
Dendrimer Templated Synthesis Of One Nanometer Rh And Pt Particles Supported On Mesoporous Silica: Catalytic Activity For Ethylene And Pyrrole Hydrogenation, Wenyu Huang, John N. Kuhn, Chia-Kuang Tsung, Yawen Zhang, Susan E. Habas, Peidong Yang, Gabor A. Somorrjai
Wenyu Huang
Monodisperse rhodium (Rh) and platinum (Pt) nanoparticles as small as ∼1 nm were synthesized within a fourth generation polyaminoamide (PAMAM) dendrimer, a hyperbranched polymer, in aqueous solution and immobilized by depositing onto a high-surface-area SBA-15 mesoporous support. X-ray photoelectron spectroscopy indicated that the as-synthesized Rh and Pt nanoparticles were mostly oxidized. Catalytic activity of the SBA-15 supported Rh and Pt nanoparticles was studied with ethylene hydrogenation at 273 and 293 K in 10 torr of ethylene and 100 torr of H2 after reduction (76 torr of H2 mixed with 690 torr of He) at different temperatures. Catalysts were active without …
Highly Selective Synthesis Of Catalytically Active Monodisperse Rhodium Nanocubes, Yawen Zhang, Michael E. Grass, John N. Kuhn, Feng Tao, Susan E. Habas, Wenyu Huang, Peidong Yang, Gabor A. Somorjai
Highly Selective Synthesis Of Catalytically Active Monodisperse Rhodium Nanocubes, Yawen Zhang, Michael E. Grass, John N. Kuhn, Feng Tao, Susan E. Habas, Wenyu Huang, Peidong Yang, Gabor A. Somorjai
Wenyu Huang
Monodisperse sub-10 nm Rh nanocubes were synthesized with high selectivity (>85%) by a seedless polyol method. The {100} faces of the Rh NCs were effectively stabilized by chemically adsorbed Br− ions from trimethyl(tetradecyl)ammonium bromide (TTAB). This simple one-step polyol route can be readily applied to the preparation of Pt and Pd nanocubes. Moreover, the organic molecules of PVP and TTAB that encapsulated the Rh nanocubes did not prevent catalytic activity for pyrrole hydrogenation and CO oxidation.
Influence Of Reaction With Xef2 On Surface Adhesion Of Al And Al2o3 Surfaces, Tianfu Zhang, Jeong Park, Wenyu Huang, Gabor A. Somoraji
Influence Of Reaction With Xef2 On Surface Adhesion Of Al And Al2o3 Surfaces, Tianfu Zhang, Jeong Park, Wenyu Huang, Gabor A. Somoraji
Wenyu Huang
The change in surfaceadhesion after fluorination of Al and Al2O3surfaces using XeF2 was investigated with atomic force microscopy. The chemical interaction between XeF2 and Al and Al2O3surfaces was studied by in situx-ray photoelectron spectroscopy. Fresh Al and Al2O3surfaces were obtained by etching top silicon layers of Si∕Al and Si∕Al2O3 with XeF2. The surfaceadhesion and chemical composition were measured after the exposure to air or annealing (at 200°C under vacuum). The correlation between the adhesion force increase and presence of AlF3 on the surface was revealed.
Time-Resolved Investigation Of The Acoustic Vibration Of A Single Gold Nanoprism Pair, J. Burgin, P. Langot, N. Del Fatti, F. Vallee, Wenyu Huang, M.A. El-Sayed
Time-Resolved Investigation Of The Acoustic Vibration Of A Single Gold Nanoprism Pair, J. Burgin, P. Langot, N. Del Fatti, F. Vallee, Wenyu Huang, M.A. El-Sayed
Wenyu Huang
The acoustic vibration of single gold nanoprism pairs on a glass substrate has been investigated in the time-domain combining a spatial modulation spectroscopy microscope with a high-sensitivity femtosecond pump−probe setup. Three modes were observed and ascribed to two in-plane and one out-of-plane vibration of the nanoprisms forming the pair, in agreement with a theoretical analysis. The periods of the two former modes with similar nature show weak (about 10%) and well correlated pair to pair fluctuations that can be unambiguously ascribed to variation of the prism geometry. In contrast, strong fluctuations, by almost a factor of 6, of the mode …
Sub-Two Nanometer Single Crystal Au Nanowires, Ziyang Huo, Chia-Kuang Tsung, Wenyu Huang, Xiaofeng Zhang, Peidong Yang
Sub-Two Nanometer Single Crystal Au Nanowires, Ziyang Huo, Chia-Kuang Tsung, Wenyu Huang, Xiaofeng Zhang, Peidong Yang
Wenyu Huang
Ultrathin single crystal Au nanowires with diameter of ∼1.6 nm and length of few micrometers were synthesized with high yield by simply mixing HAuCl4 and oleylamine at room temperature. High resolution transmission electron microscopy studies revealed that all of these nanowires are single crystalline and grew along the [111] direction. The valency evolution of the gold species during the synthesis was studied by X-ray photoelectron spectroscopy, which showed a clear Au3+ → Au+ → Au stepwise reduction at different reaction stages. Small angle X-ray scattering and small-angle X-ray diffraction suggest mesostructure formation upon HAuCl4 and oleylamine mixing. The slow in …
Posterminaries: More Or Less Modern, Alexander H. King
Posterminaries: More Or Less Modern, Alexander H. King
Alexander H. King
It is yet another sign that I am aging. More and more often when young researchers hand me a written report of their research, I find myself criticizing their introductory section: “You need to start your literature survey with the original papers on this topic. Go and read…” followed by a citation to some classic of the learned literature.
Non-Destructive Horseradish Peroxidase Immobilization In Porous Silica Nanoparticles, Rebecca Voss, Michael A. Brook, Jordan Thompson, Yang Chen, Robert H. Pelton, John D. Brennan
Non-Destructive Horseradish Peroxidase Immobilization In Porous Silica Nanoparticles, Rebecca Voss, Michael A. Brook, Jordan Thompson, Yang Chen, Robert H. Pelton, John D. Brennan
Rebecca Cademartiri
The preparation of protein doped silica particles is impeded by the difficulty of incorporating proteins within the silica mesostructure under conditions that do not lead to denaturation. Herein, the synthesis of spherical silica particles (diameter 150 nm–550 nm) under protein friendly conditions in a one step process is described. Diglyceroxysilane (DGS) was reacted in ethanol and methanol-free conditions in pure water or in buffer solutions with or without the presence of additional glycerol. Stabilization of the particles, consistent with steric stabilization, was obtained using poly(ethylene glycol) (PEG) of various molecular weights and with various end groups, including allyl and (CH2)3Si(OEt)3 …
Control Of Porosity In Fluoride Thin Films Prepared By Vapor Deposition, Alexander H. King
Control Of Porosity In Fluoride Thin Films Prepared By Vapor Deposition, Alexander H. King
Alexander H. King
We have measured the porosity in thin films of lithium fluoride (LiF), magnesium fluoride (MgF2), barium fluoride (BaF2), and calcium fluoride (CaF2) as a function of the substrate temperature for films deposited by thermal evaporation onto glass substrates. The amount of porosity in the thin films was measured using an atomic force microscope and a quartz crystal thickness monitor. The porosity was very sensitive to the substrate temperature and decreased as the substrate temperature increased. Consistent behavior was observed among all of the materials in this study.
Posterminaries: Full Circle, Alexander H. King
Posterminaries: Full Circle, Alexander H. King
Alexander H. King
A few years ago, I was walking near the old Union Station in Pittsburgh with a colleague only slightly younger than myself, when we happened upon some large-scale relics of the steel industry displayed for public viewing. “You don’t see too many of those in public parking lots,” I offered. “Um… what is it?” was the response. I suppose I was just a little surprised that a prominent materials scientist did not recognize a Bessemer converter—arguably the principal source of wealth during the U.S. industrial revolution—but this conversation took place back when steel was in decline, and many university Materials …
Thermal Effects On Mechanical Grinding-Induced Surface Texture In Tetragonal Piezoelectrics, Wonyoung Chang, Alexander H. King, Keith J. Bowman
Thermal Effects On Mechanical Grinding-Induced Surface Texture In Tetragonal Piezoelectrics, Wonyoung Chang, Alexander H. King, Keith J. Bowman
Alexander H. King
The effect of temperature on grinding-induced texture in tetragonal lead zirconate titanate (PZT) and lead titanate (PT) has been investigated using in situ x-ray diffraction (XRD) with an area detector. In contrast with previous results on electrical poling, mechanically-ground PT and soft PZT materials retain strong ferroelastic textures during thermal cycling, even after excursions to temperatures slightly above the Curie temperature. The relationship between the residual stresses in the surface region, caused by grinding, and those resulting from domain wall motion is elucidated by in situ texture measurements obtained during thermal cycling.