Vapor Sorption and Electrical Response of Au-Nanoparticle-Dendrimer Composites

摘要

Films comprising Au nanoparticles and polyphenylene dendrimers (first and second generation) are deposited onto transducer substrates via layer-by-layer self-assembly and characterized by atomic force microscopy and X-ray photoelectron spectrosco-py. Their sorption behavior is studied by measuring the uptake of solvents from the vapor phase with quartz crystal microba-lances (QCMs). The resistance of the films is simultaneously monitored. Both sensor types, QCMs and chemiresistors, give qualitatively very similar response isotherms that are consistent with a combination of Henry- and Langmuir-type sorption processes. The sorption-induced increase in relative differential resistance scales linearly with the amount of analyte accumulated in the films. This result is in general agreement with an activated tunneling process for charge transport, if little swelling and only small changes in the permittivity of the film occur during analyte sorption (a first-order approximation). The relative sensitivity of the films to different solvents decreases in the order toluene ≈ tetrachloroethylene > 1-propanol water. Films containing the larger second-generation dendrimers show higher sensitivity than films containing first-generation dendrimers.