Light-Induced Formation of Silver Particles and Clusters in Crosslinked PVA/PAA Films

Abstract

Thin films able to sustain an efficient photoreduction of Ag+ ions with 350 nm photons in air were prepared by crosslinking poly(vinyl alcohol) with glutaraldehyde in the presence of poly(acrylic acid). Standard colloid techniques served as screening methods for the selection of polymer compositions yielding films with desired properties. When present at high concentrations, Ag+ ions were reduced at room temperature in the films by poly(vinyl alcohol) but poly(acrylic acid) inhibited the slow dark reaction. Optical signals with maxima above 400 nm resulted from both reduction processes. The available evidence confirmed that they originated from nanometer-sized metal particles and is inconsistent with results for other proposed chromophores. An additional absorption centered at 280 nm that formed only under illumination was assigned to Ag3+ clusters. Small Ag crystallites with similar size distributions and with an average diameter of 5 nm were the main product of the photoreduction in non-crosslinked or c...