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Nanoparticles

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Articles 31 - 38 of 38

Full-Text Articles in Inorganic Chemistry

Stable Aqueous Nanoparticle Film Assemblies With Covalent And Charged Polymer Linking Networks, Lesley E. Russell, Anne A. Galyean, Sherilyn M. Notte, Michael C. Leopold Jun 2007

Stable Aqueous Nanoparticle Film Assemblies With Covalent And Charged Polymer Linking Networks, Lesley E. Russell, Anne A. Galyean, Sherilyn M. Notte, Michael C. Leopold

Chemistry Faculty Publications

The construction of highly stable and efficiently assembled multilayer films of purely water soluble gold nanoparticles is reported. Citrate-stabilized nanoparticles (CS-NPs) of average core diameter of 10 nm are used as templates for stabilization-based exchange reactions with thioctic acid to form more robust aqueous NPs that can be assembled into multilayer films. The thioctic acid stabilized nanoparticles (TAS-NPs) are networked via covalent and electrostatic linking systems, employing dithiols and the cationic polymer poly(l-lysine), respectively. Multilayer films of up to 150 nm in thickness are successfully grown at biological pH with no observable degradation of the NPs within the film. The …

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Crown Ether-Metal ‘Sandwiches’ As Linking Mechanisms In Assembled Nanoparticle Films, Rebecca R. Pompano, Phillip G. Wortley, Leslie M. Moatz, D. J. Tognarelli, Kevin W. Kittredge, Michael C. Leopold Jul 2006

Crown Ether-Metal ‘Sandwiches’ As Linking Mechanisms In Assembled Nanoparticle Films, Rebecca R. Pompano, Phillip G. Wortley, Leslie M. Moatz, D. J. Tognarelli, Kevin W. Kittredge, Michael C. Leopold

Chemistry Faculty Publications

Crown ether ligands attached to monolayer-protected clusters (MPCs) were assembled as films and the linking mechanism between the crown ether–metal ion–crown ether bridges between nanoparticles was examined. Thicker films exhibited a red shift in the absorbance maximum for the surface plasmon band which was attributed to the increasing aggregation and cross linking within the film. Quantized double layer charging peaks suggest that film growth is selective toward a specific core size or exchange rate, either of which affect the number of potential linking ligands in the periphery of the MPCs. Multi-layer growth of films was only achieved with metal ions …

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Covalently Networked Monolayer Protected Nanoparticle Films, D. J. Tognarelli, Robert B. Miller, Rebecca R. Pompano, Andrew F. Loftus, Daniel J. Shiebley, Michael C. Leopold Oct 2005

Covalently Networked Monolayer Protected Nanoparticle Films, D. J. Tognarelli, Robert B. Miller, Rebecca R. Pompano, Andrew F. Loftus, Daniel J. Shiebley, Michael C. Leopold

Chemistry Faculty Publications

No abstract provided.

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Distance-Dependent Electron Hopping Conductivity And Nanoscale Lithography Of Chemically-Linked Gold Monolayer Protected Cluster Films, Francis P. Zamborini, Laura E. Smart, Michael C. Leopold, Royce W. Murray Oct 2003

Distance-Dependent Electron Hopping Conductivity And Nanoscale Lithography Of Chemically-Linked Gold Monolayer Protected Cluster Films, Francis P. Zamborini, Laura E. Smart, Michael C. Leopold, Royce W. Murray

Chemistry Faculty Publications

Films of monolayer protected Au clusters (MPCs) with mixed alkanethiolate and ω-carboxylate alkanethiolate monolayers, linked together by carboxylate–Cu2+–carboxylate bridges, exhibit average edge-to-edge cluster spacings that vary with the numbers of methylene segments in the alkanethiolate ligand as determined by a combined atomic force microscopy (AFM)/UV-Vis spectroscopy method. The electronic conductivity (σEL) of dry films is exponentially dependent on the cluster spacing, consistent with electron tunneling through the alkanethiolate chains and non-bonded contacts between those chains on individual, adjacent MPCs. The calculated electronic coupling factor (β) for tunneling between MPCs is 1.2 Å−1, which is similar to …

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Growth, Conductivity, And Vapor Response Properties Of Metal Ion-Carboxylate Linked Nanoparticle Films, Michael C. Leopold, Robert L. Donkers, Dimitra Georganopoulou, Megan Fisher, Francis P. Zamborini, Royce W. Murray Aug 2003

Growth, Conductivity, And Vapor Response Properties Of Metal Ion-Carboxylate Linked Nanoparticle Films, Michael C. Leopold, Robert L. Donkers, Dimitra Georganopoulou, Megan Fisher, Francis P. Zamborini, Royce W. Murray

Chemistry Faculty Publications

Nanoparticles of metals (Au, Ag, Pd, alloys) in the size range 1–3 nm diameter can be stabilized against aggregation of the metal particles by coating the metal surface with a dense monolayer of ligands (thiolates). The stabilization makes it possible to analytically define the nanoparticle composition (for example, Au140(hexanethiolate)53, I) and to elaborate the chemical functionality of the protecting monolayer (for example, Au140(C6)35(MUA)18, II, where C6 = hexanethiolate and MUA = mercaptoundecanoic acid). Network polymer films (IIfilm) on interdigitated array electrodes can be prepared from II, based on cation coordination (i.e., Cu2+, Zn2+, Ag+, methyl viologen) by the …

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Simulations Of Quantized Double Layer Charging Voltammetry Of Poly Disperse And Mono-Disperse Monolayer Protected Clusters, Deon T. Miles, Michael C. Leopold, Jocelyn F. Hicks, Royce W. Murray Jan 2003

Simulations Of Quantized Double Layer Charging Voltammetry Of Poly Disperse And Mono-Disperse Monolayer Protected Clusters, Deon T. Miles, Michael C. Leopold, Jocelyn F. Hicks, Royce W. Murray

Chemistry Faculty Publications

This paper describes simulated differential pulse voltammetry (DPV) of quantized double-layer charging (QDL) in poly-disperse monolayer-protected gold cluster (MPC) solutions. The simulation accounts for the voltage spacing between QDL peaks with a concentric sphere capacitor model, in which core sizes, and the relative proportion of each size, are input using transmission electron microscopy (TEM) data. MPC diffusion coefficients are estimated from hydrodynamic radii, and peaks are broadened to account for DPV pulse height effects. The smallest MPCs are omitted from the simulation because electrochemical HOMO/LUMO gap information is uncertain. The largest ones are shown to produce the underlying DPV current …

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Hplc Of Monolayer-Protected Gold Nanoclusters, Victoria L. Jimenez,, Michael C. Leopold, Carolyn Mazzitelli, James W. Jorgenson, Royce W. Murray Dec 2002

Hplc Of Monolayer-Protected Gold Nanoclusters, Victoria L. Jimenez,, Michael C. Leopold, Carolyn Mazzitelli, James W. Jorgenson, Royce W. Murray

Chemistry Faculty Publications

Polydisperse samples of Au nanoparticles protected with monolayers of hexanethiolate ligands (C6 MPCs) and with mixed monolayers of hexanethiolate and mercaptounde- canoic acid (C6/MUA MPCs) have been chromatographically separated using C8 120-Å columns and acetone/toluene mobile phase. The spectral details of eluted peaks and of quantized double-layer charging features in the differential pulse voltammetry of collected fractions were used to show that the elution orders of C6 MPC mixtures and of C6/MUA MPC mixtures were different. For C6 MPCs, the smallest MPCs were eluted first, whereas the smallest C6/MUA MPCs were eluted last. The reversal of order of elution was …

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Electron Hopping Conductivity And Vapor Sensing Properties Of Flexible Network Polymer Films Of Metal Nanoparticles, Francis P. Zamborini, Michael C. Leopold, Jocelyn F. Hicks, Pawel J. Kulesza, Marcin A. Malik, Royce W. Murray Jun 2002

Electron Hopping Conductivity And Vapor Sensing Properties Of Flexible Network Polymer Films Of Metal Nanoparticles, Francis P. Zamborini, Michael C. Leopold, Jocelyn F. Hicks, Pawel J. Kulesza, Marcin A. Malik, Royce W. Murray

Chemistry Faculty Publications

Films of monolayer protected Au clusters (MPCs) with mixed alkanethiolate and ω-carboxylate alkanethiolate monolayers, linked together in a network polymer by carboxylate-Cu2+-carboxylate bridges, exhibit electronic conductivities (σEL) that vary with both the numbers of methylene segments in the ligands and the bathing medium (N2, liquid or vapor). A chainlength-dependent swelling/contraction of the film's internal structure is shown to account for changes in σEL. The linker chains appear to have sufficient flexibility to collapse and fold with varied degrees of film swelling or dryness. Conductivity is most influenced (exponentially dependent) by the chainlength of the nonlinker (alkanethiolate) ligands, a result consistent …

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