Development of a transparent silica-titania-methyl siliconate nanocoating with photocatalytic-hydrophobic properties aided by response surface method

This work aims to optimize the factors affecting silica-titania-methyl siliconate photocatalyst hydrophobic coatings prepared through a straightforward chemical method using tetraethyl-orthosilicate (TEOS: C8H20O4Si), tetraethyl-orthotitanate (TEOT: C8H20O4Ti) and potassium methyl siliconate (PMS: CH3SiO3K3). Field Emission- Scanning electron microscopy (FE-SEM) images showed that a uniform and crack-free coating with a thickness of nearly 90 nm was formed on the surface at the low temperature. FT-IR spectroscopy confirmed the formation of silica and titania particles on the coating. Response Surface Method (RSM) with 29 experiments was implemented, and the contact angle with photocatalytic efficiency was considered as the response to be optimized. Four effective factors of the mole ratio of TEOT/TEOS, PMS/TEOS, H2O/TEOS, and pH were determined in three levels, which were equal to 35, 0.06, 5.5, and 2, respectively, obtained by an Analysis of Variance (ANOVA) over the experiment results. In the mentioned conditions, the expected result for the contact angle and photocatalytic efficiency were 139˚ and 43.5%, respectively, and the confirmation test reached 141° and 41%. Consequently, TEOT/TEOS and PMS/TEOS molar ratios were found to be the most effective factors in both photocatalytic and hydrophobicity of the coating.