Electron Hopping Conductivity and Vapor Sensing Properties of Flexible Network Polymer Films of Metal Nanoparticles

Abstract

Films of monolayer protected Au clusters (MPCs) with mixed alkanethiolate and omega-carboxylate alkanethiolate monolayers, linked together in a network polymer by carboxylate-Cu2+-carboxylate bridges, exhibit electronic conductivities (sigma(EL)) 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 sigma(EL). 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 with electron tunneling through the alkanethiolate chains and nonbonded contacts between those chains on individual, adjacent MPCs. The sigma(EL) results concur with the behavior of UV-vis surface plasmon adsorption bands, which are enhanced for short nonlinker ligands and when the films are dry. The film conductivities respond to exposure to organic vapors, decreasing in electronic conductivity and increasing in mass (quartz crystal microgravimetry, QCM). In the presence of organic vapor, the flexible network of linked nanoparticles allows for a swelling-induced alteration in either length or chemical nature of electron tunneling pathways or both.

Photochemically reduced polyoxometalate assisted generation of silver and gold nanoparticles in composite films: a single step route

“…Because these materials exhibit novel combinations of metal particle and polymer properties that are attractive for applications in nonlinear optics [11], photo imaging and patterning [12], glazing elements for sunlight control and magnetic devices [13,14], sensor fabrication [15], antimicrobial coatings [16], and catalysis [17]. The dispersed metal nanoparticles into polymers in non-aggregated form, with small diameters allow the preparation of materials with reduced light characteristic properties for applications as optical filters, linear polarizers, and optical sensors.…”

Electrical Resistivity of Assembled Transparent Inorganic Oxide Nanoparticle Thin Layers: Influence of Silica, Insulating Impurities, and Surfactant Layer Thickness

“…Several works focused on understanding the influence of molecules, 36,37 polymers [38][39][40] and insulating barriers on the conductivity in nanoparticle composites. Models for percolation and hopping of electrons through nanoparticle assemblies have been investigated.…”

Location Control of Nanoparticles Using Combination of Top-down and Bottom-up Nano-fabrication

“…Also, gold allows for the covalent attachment of thiolated ligands to the particle surface [21,22]. The optical and electrical properties of layer by layer self-assembled films comprised of Au or Ag nanoparticles and various organic compounds have been investigated [23][24][25][26][27][28][29]. Furthermore, layer-by-Layer self-assembly of composite thin films of cadmium sulfide nanoparticle and alkanedithiol was achieved on a gold substrate by an alternate immersion into solutions of dithiols and solution containing CdS nanoparticle [30,31].…”