Metal-nanocrystal-containing polymer composite

Metal-polymer systems obtained as a result of vapor deposition cryochemical synthesis contain stabilized small nonmetallic clusters of metal atoms and metal nanocrystals, but only metal nanocrystals participate in conductivity processes. The data on Ag-containing PPX composites [44] testify to the fact that the relative part of metal stabilized in cluster form at ambient temperature sharply decreases with increasing total metal content even in the range 0-2 vol. %. Therefore, at measurements of conductivity, which were carried out at considerably higher metal concentrations, it was accepted that as a first approximation, all metal is as nanocrystals. 

When metal particles are isolated in a polymer so that the interaction between them can be neglected, the conductivity of a composite is determined by that of a polymer matrix. In such composites, metal nanoparticles can only inject carriers into a polymer but do not influence substantially the conductivity process [59], This is the case of metal-PPX films prepared by the cryochemical vapor deposition teclmique if such films contain metal or semiconductor nanocrystals in amounts less than 4—5 vol. % [30]. The conductivity of such composites follows classical olmfic current-voltage relationship [30] and Arrheiuus dependence on temperature [57]. At higher metal contents the mechaiusm of conductivity in synthesized composite films changes under influence of the interparficle interaction. In PPX films containing Pb nanoparficles in amounts from 5 to 10 vol. %, the dependence of current I on voltage U looks like In / [30]. This dependence is characteristic for a... 

Cryochemically synthesized PPX films containing metal or semiconductor nanocrystals have a fine porous structure caused by features of solid-state polymerization. Due to this structure, molecules of gaseous substances readily penetrate into polymer film from the environment. Synthesized composite films demonstrate valuable strong sensor effects resulting from a marked influence of some low-molecular-weight molecules, diffusing into the polymer and adsorbed onto nanocrystals, on the film conductivity [4, 30, 62-64]. Such effects are characteristic of films whose conductivity is governed by electron transfer between nanoparticles. 

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