Organo-silica–titania nanocomposite elaborated by sol–gel processing with tunable optical properties

Organically modified silica–titania thin films were elaborated by a sol–gel process and UV assisted photopolymerisation. Two different chelating agents, methacrylic acid (MAA) and a β-diketone (2-(methacryloyloxy) ethyl acetoacetone (MAEA)) were compared in this work. It was demonstrated that the choice of the chelating agent is a key parameter to increase the molar ratio Si:Ti and therefore raise the refractive index of the material. β-Diketone has proven to be a good candidate to stabilise the titanium precursor and its effects were compared to those observed with methacrylic acid. Fourier transform infrared spectroscopy was used to monitor the material formation and modification upon irradiation. M-lines spectroscopy was used to measure the refractive index of the material that varied between 1.51 and 1.59 depending on the titanium molar concentration. Optical properties were analysed in view of applications in the field of micro-optics and optical coatings.