The Thesis explores the photochromic properties of titanium dioxide nanoparticles in different environments. It was seen that the environment in which the nanoparticles are dispersed as well as the modification of the nanoparticles have a profound effect on the photochromic properties and can change both the photodarkening and recovery kinetics as well as influence the electrical properties of the nanoparticles. Furthermore, the incorporation of the nanoparticles into organic gels was achieved while retaining high transparency and the photochromic properties of the nanoparticles.