Reversible Photochromism of Sol-Gel SiO₂: AgCl Films

Glass films containing silver chloride were prepared by the sol gel method. The films darkened upon irradiation with sunlight or UV-light and were bleached reversibly by exposed to nitric acid vapors. The mechanism of the reversible bleaching is deduced from optical spectra, x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS). The silver chloride particles that were dispersed isotropically before exposure to light acquire a preferred orientation after repeating darkening and bleaching cycles.