Silica–gelatin bio-hybrid and transparent nano-coatings through sol–gel technique

Silica–gelatin nano-hybrid composites are reported where the synthesis has been done through hydrolysis of tetraethoxysilane (TEOS) in presence of gelatin solution. Chemical interaction between silica and gelatin, gelation characteristics, rheological behaviour of the sol, thermal decomposition of the nanocomposites, porosity features, optical transmittance and thickness of the coatings are reported. FTIR spectra show that the interaction of silica and gelatin is through the hydrogen bonding of CO and N–H groups of gelatin to the silanol hydrogen. However at higher pH, electrostatic interaction between negatively charged silica and gelatin leads to the precipitation of silica. Thermal analysis data show that certain amount of water in the hydrolysed silica precursor is replaced by gelatin molecules and the decomposition of gelatin takes place above 315 °C. We could get a surface area as large as 350 m2 g−1 for silica–gelatin hybrid even without calcination. Coatings of silica–gelatin composite hybrid developed on glass surface has thickness of 300 nm and were found to be >90% transparent as evidenced by optical transmittance measurements. Further the coating can be applied to biological substrates such as leather.