Highly transparent hard bio-coating synthesized by low temperature sol–gel process

Highly transparent silica–titania films with dense and mesoporous structures were prepared by the sol–gel process. The films were prepared by a single spin coating process using mixed silica–titania sols, followed by annealing at 180 °C. The transmittances of both films were higher than 97% in the UV–visible-IR range. The refractive index of the dense film measured by ellipsometry was 1.87–1.59 in the range of 300–1100 nm (1.63 at 500 nm). The pencil hardness test showed that the hardnesses of the dense and porous films were over 9H and 3B, respectively. The cytotoxicity test (MTT assay) showed that both films had no poisonous effect on the living cells. From the surface composition analysis by X-ray photoelectron spectroscopy, SiO2 was found to exist on the film surface which could be responsible to the good biocompatibility of the film.