Changes in the Chemical and Structural Properties of Nanocomposite Ag:TiO2 Films during Photochromic Transitions

This study focuses on changes in the oxidation state of silver and in the crystalline phase of TiO2 occurring during the photochromic transitions of amorphous nanocomposite mesoporous Ag:TiO2 films exposed to ultraviolet and visible laser light. The chemical and phase transformations have been investigated by ultraviolet–visible spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, high-angle annular dark field scanning transmission electron microscopy, and high-resolution transmission electron microscopy. The results bring to the fore the presence of both silver nanoparticles in face-centered cubic and hexagonal crystalline phases during the photochromic transitions and a large amount of oxidized silver nanoparticles after visible light exposure, along with nucleation of some TiO2 crystals despite the very low intensity used.