Surface treatment of TiO2 nanoparticles via sol–gel method: Effect of silane type on hydrophobicity of the nanoparticles

•TiO2 nanoparticles were treated with three different fluoroalkylsilane precursors.•Nanoparticles were characterized via FTIR, TGA, XPS spectroscopy, and TEM technique.•The adsorption mechanism for alkaline and acidic conditions was proposed.•Type of fluoroalkylsilane and pH of the reaction media affect on TiO2 adsorption. Hydrophobic TiO2 nanoparticles are important elements in preparation of functional organic coatings. In fact, hydrophobicity of the nanoparticle helps to optimize the photoactivity of the coating while maintaining its durability. In this study, surface treatment of the commercial TiO2 nanoparticles was carried out using various silane precursors via sol–gel method in both acidic (pH 2) and alkaline media (pH 12). A long aliphatic chain (F1), a short aliphatic chain (F2), and an aromatic (F3) fluorosilane were used for this purpose. The treated nanoparticles were characterized using Fourier transform infrared and X-ray photoelectron spectroscopy, thermal gravimetric analysis, and transmission electron microscopy. Hydrophobicity of the treated nanoparticles was evaluated by floating in de-ionized water. The results showed that the adsorption of F1 on TiO2 only takes place in the alkaline condition while F3 is adsorbed in both alkaline and acidic conditions. Furthermore, no significant adsorption for F2 was detected neither in alkaline nor acidic conditions. The floatation results revealed a hydrophobic nature for F1 and F3 treated nanoparticles, however, nanoparticles attempted with F2, remained hydrophilic. It was concluded that the hydrophobicity of the nanoparticles is affected by both chemical nature of fluorosilane as well as pH of the treatment media.