A study of photoreactions in photosensitive TiO₂ hybrid gel films induced by UV irradiation

Abstract

Photosensitive TiO₂ gel films containing β-diketones and monomers with unsaturated hydrocarbons exhibit photosensitivity and can be patterned by photolithography. Photosensitive TiO₂ gel films containing dibenzoylmethane (DBM) and methacrylic acid (MA) were prepared by the sol–gel method. The photoreactions of the gel films under ultraviolet (UV) light were investigated by UV–Vis, infrared, Raman, nuclear magnetic resonance, and X-ray absorption fine structure spectroscopic measurements. UV irradiation causes the chelate rings between titanium alkoxide and DBM or MA to decompose without drastic changes in the coordination number of Ti and in Ti–O distances, and it causes the formation of Ti–O–Ti networks. MA is photopolymerized by radicals resulting from the decomposition of DBM. These structural changes induced by UV irradiation cause the alcohol solubility of the materials to differ, and they allow fine patterns to be formed by etching.