Antireflective coating based on TiO2 nanoparticles modified with coupling agents via acid-catalyzed sol-gel method

TiO2 - based materials were synthesized via acid-catalyzed sol-gel method using tetraethoxysilane (TEOS) and/or methyltriethoxysilane (MTES) - as silane coupling agents. The physical and chemical properties of the obtained TiO2 - based materials were characterized through FT-IR and UV-Vis spectroscopy, TGA, AFM analysis and contact angle measurements. FT-IR spectra demonstrated that the silane coupling agents react via a crosslink and covalently bond on the TiO2 surface. TGA analysis of samples was used to investigate the effect of addition of silane precursor into the TiO2 matrix. Diffuse reflectance spectra revealed that the addition of silane agents improved the antireflective properties of obtained thin films. Water contact angle of TiO2 - based materials showed that the wettability of the thin films was influenced by the addition of TEOS and/or MTES during the modification process. AFM images showed smooth surfaces (RMS roughness up to 3 nm) but with morphological peculiarities depending on the chemical modification, with TEOS, MTES or both, of the TiO2 parental matrix. Transparent and hydrophobic coatings were obtained with MTES addition in the modification process of TiO2 nanoparticles via acid-catalyzed sol-gel method.