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.

Brewster angle microscopy (BAM) studies on dipalmitoyl phosphatidyl glycerol (DPPG, sodium salt) monolayers on water subphases containing different amounts of NaCl are presented. Inhomogeneities in the monolayer appear after spreading at large mean areas per lipid molecule and at electrolyte concentrations in the subphase lower than 0.15 M NaCl. It is assumed that (i) after spreading DPPG is completely hydrolyzed, (ii) dissociation of the resulting acid depends on the electrolyte concentration in the subphase, and (iii) nondissociated acid molecules form solidlike aggregates in the monolayer, while the dissociated part surrounds them. Image processing of the BAM images allows us to calculate the surface densities of the lipid in the coexisting states, and the dissociation constant of the lipid in the monolayer ( ). The electrostatic contribution to the surface pressure was estimated using the obtained value. Comparison with the experimental π/A isotherms shows satisfactory agreement, confirming the value of the determined dissociation constant. We concluded that the described procedure is useful for the determination of for monolayers of charged surfactant molecules.

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In the present work, specular neutron reflectometry was used to study the sorption of D2O and perdeuterated toluene in self-assembled Au nanoparticle/poly(amidoamine) composite films. The method provides information about analyte-induced film swelling and analyte distribution profiles across the films. Our data suggest that film swelling upon exposure to the analytes is negligible within the resolution of the method. Strong differences are observed between the distribution profiles of D 2O and toluene-d8. Water penetrates into the film with an exponentially decaying concentration profile. In contrast, toluened 8 forms a thin "wetting" layer on top of the film, while the bulk of the film remains essentially analyte free. These results are explained by taking into account the chemical structure of the dendritic polymer used for film preparation.