Patent ID: 8617435

Claim:
A sol-gel process for the production of a photochromic composite material, comprising the steps of: selecting an alkoxysilane as a precursor, selecting a ruthenium complex with a nitrosyl ligand is selected as a photochromic complex, and, in combination, starting the sol-gel process by providing the selected precursor and the selected photochromic complex, with successive stages of hydrolysis, arrangement in a container of a selected shape, condensation, curing and aging, whereby a latter stage includes a final drying cycle, and for the stages of curing and aging, pH, temperature and duration are selected so xerogel that is produced, whose shape is determined by that of the container, the photochromic ruthenium complex with the nitrosyl ligand, in a crystalline state and in form of nanoparticles, is inserted into nanopores of silica matrix, distributed in an at least substantially homogeneous way.