Characterisation and spectral properties of surface adsorbed phenosafranine dye in zeolite-Y and ZSM-5: photosensitisation of embedded nanoparticles of titanium dioxide

Abstract

Synthesis, characterisation and photosensitisation of titanium dioxide nanoparticles by phenosafranine dye adsorbed on the external surfaces of microporous materials were carried out. Titanium dioxide nanoparticles were anchored on the external surface as well as encapsulated in the cavities of porous zeolites. The composite materials are characterized using powder XRD and UV-visible diffuse reflectance spectroscopy. The organic dye phenosafranine is used as visible light absorbing sensitiser. Photosensitisation of the titanium dioxide nanoparticles deposited on the external surface of the microporous silicates are effected by the singlet excited states of phenosafranine and the mechanism of photosensitization is suggested to be static in nature. Photosensitisation of the TiO₂ nanoparticles encapsulated in the cavities of the host is more efficient. In the case of the sensitisation of the TiO₂ nanoparticles encapsulated inside the zeolite framework, the process is facilitated by the interaction between the host lattice with adsorbed water molecules and the excited state of the dye molecules at the outer surface of the host. The present investigation for the first time reports on the sensitization of TiO₂ nanoparticles by the organic dye separated in space by the insulator host material.