Photochromic properties in silver-doped titania nanoparticles

The Ag-doped TiO₂ nanoparticles were synthesized at room temperature using a solution of titanium isopropoxide and silver nitrate as precursors. The inclusion of Ag in the nanocrystalline TiO₂ lattice was systematically analyzed both from a morphological and a structural point of view. Raman spectroscopy, electron microscopy, electronic diffraction and x-rays allow us to testify that the dopant Ag does not modify the nanocrystalline anatase tetragonal structure of the nanoparticles, but causes a small distortion of the structure. UV–vis spectroscopy allowed to analyze the optical properties of the obtained nanoparticles. Kubelka Munk's model allowed the interpretation of diffuse reflectance spectra. We have obtained a very different system from the hetero-system Ag-TiO₂ described in the literature, but it shows an interesting photochromic behaviour. Ag-doped TiO₂ nanoparticles darken and whiten under UV light and visible light, respectively, in a very fast way. A simple kinetic model has been used to process experimental data and describe the observed photochromic process and to determine the darkening and whitening constants. (paper)