X-ray Induced Formation of Metal Nanoparticles from Interpolyelectrolyte Complexes with Copper and Silver Ions: The Radiation-Chemical Contrast

Abstract

Tuning the size and spatial distribution of metal nanoparticles is a key issue for obtaining metal–polymer nanocomposites with desirable properties. It was shown that the action of white X-ray radiation (bremsstrahlung, Emax ∼ 30 keV) on swollen films of interpolyelectrolyte complexes with copper and silver ions in an aqueous—alcoholic environment resulted in the formation of a specific type of metal nanostructures characterized by transmission electron microscopy (TEM). The structure pattern was explained by autocatalytic enhancement of the rate of chemical transformations in the vicinity of preformed metal nanoparticles. The effect was attributed to increasing absorption of X-ray photons by compact metal nanoparticles leading to local sensitization described as the radiation-chemical contrast. The nanostructure pattern exhibited a remarkable evolution with increasing irradiation dose. In particular, at a certain stage, the big primary nanoparticles induce formation of “clouds” of ultrasmall secondary particles due to local distribution of the secondary electrons. The scale of the radiation-induced events is determined by the photon energy and electronic properties of absorbers. In the case of copper ions, major interaction occurs with K-electrons, whereas the interactions with both K- and L-electrons are significant for silver ions, which results in bimodal distribution of nanoparticle size.