title: Gold-nanoparticle/organic linker films: self-assembly, electronic and structural characterisation, composition and vapour sensitivity.
abstract: Gold-nanoparticle/organic films were prepared via layer-by-layer self-assembly using dodecylamine-stabilised Au-nanoparticles and poly(propyleneimine) (PPI) dendrimers of generation one to five (G1-G5) or hexadecanedithiol (HDT) as linker compounds. TEM and FE-SEM images revealed that the bulk of the films consisted of nanoparticles with diameters of about 4 nm. XPS was used to study the chemical composition of the films. The C 1s and N 1s signals of an AuPPI-G4 film were interpreted qualitatively according to the dendrimer structure. The absence of the nitrogen signal in case of an AuHDT film indicated that the dodecylamine ligands were quantitatively exchanged during film assembly. About 76% of the sulfur atoms were bound to the nanoparticles. the remainder being present as free thiol (S H) groups. All films displayed linear current voltage characteristics and Arrhenius-type activation of charge transport. The conductivities of the AuPPI films decreased exponentially over approximately two orders of magnitude (6.8 x 10(-2) to 1.0 x 10(-3) ohms(-1) cm(-1)) with a five-fold increase of the dendrimer generation number. Dosing the films with solvent vapours caused their resistances to increase. Using different solvent vapours demonstrated that the sensitivity of this response was determined by the solubility properties of the linker compounds. Microgravimetric measurements showed that absorption of analyte was consistent with a Langmuir adsorption model. These measurements also revealed a linear correlation between the electrical response (deltaR/Rini) and the concentration of absorbed analyte. The absorption of d4-methanol from a saturated vapour atmosphere was studied by neutron reflectometry with an AuPPI-G4 film. This measurement indicated condensation of methanol on top of the film and a uniform distribution of the analyte across the film thickness.
authors.affiliation: Materials Science Laboratories, Sony International (Europe) GmbH, Hedelfinger Str. 61, D-70327 Stuttgart, Germany.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Joseph
authors.forename: Nadejda
authors.initials: N
authors.lastname: Krasteva
authors.forename: Isabelle
authors.initials: I
authors.lastname: Besnard
authors.forename: Berit
authors.initials: B
authors.lastname: Guse
authors.forename: Miriam
authors.initials: M
authors.lastname: Rosenberger
authors.forename: Ute
authors.initials: U
authors.lastname: Wild
authors.forename: Axel
authors.initials: A
authors.lastname: Knop-Gericke
authors.forename: Robert
authors.initials: R
authors.lastname: Schlögl
authors.forename: Rumen
authors.initials: R
authors.lastname: Krustev
authors.forename: Akio
authors.initials: A
authors.lastname: Yasuda
authors.forename: Tobias
authors.initials: T
authors.lastname: Vossmeyer