Photogeneration Kinetics of Ag Nanoparticles in Light Sensitive Polymer Films

The kinetics of Ag nanoparticle photogeneration inside optically transparent thin polymer films was studied. Light sensitive polymer films able to initiate the reduction of Ag ions were prepared by blending poly(vinyl alcohol), PVA, and sulphonated poly(ether etherketone), SPEEK. Photolysis of such films with 350 nm photons produced benzophenyl ketyl (BPK) radicals of SPEEK, which are strong reducing agents able to transform silver ions into metal particles. Photoreduction of Ag ions proceeds in the films through a monophotonic process which is not affected by the presence of oxygen. The photogeneration of small Ag crystallites is characterized by an activation energy typical of free radicalreactions. At temperatures higher than the glass transition temperature of PVA a second reaction channel becomes important. This high temperature process occurs in the dark and is a self-accelerated reaction catalyzed by Ag nanoparticles present in the films.