Photochromic silver nanoparticles in titania

In this article, we present our recent work on photochromic thin films made of silver nanoparticles embedded in titania. Using optical spectroscopy we measure the photochromic changes induced by laser irradiation at various power densities and irradiation times. It is shown that illumination leads to a reduction of the extinction peak of the photoexcited particles, accompanied by a blueshift of the plasmon line. The intensity dependence of this photochromic behavior indicates that it is due to a one-photon process. Microscopically the photochromic process is explained by a plasmon-assisted electron emission from the Ag nanoparticles into the titania matrix, leading to a structural and/or compositional transformation of the nanoparticles. At large power densities, the plasmon resonance is completely bleached, indicating complete transformation, and absorption in the near-infrared is increased