Enhanced visible light-induced hydrophilicity in sol–gel-derived Ag–TiO2 hybrid nanolayers

Silver-doped TiO2 hybrid nanolayers (NLs) were prepared via the sol–gel method using TiCl4 as a precursor, and the products were characterized by X-ray diffraction, atomic force microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. A detailed study of the visible light hydrophilicity of Ag–TiO2 NLs by evaluating the contact angle of water droplets on the surface of the layers has been performed. Furthermore, a series of experiments was carried out in order to find the optimum value of dopant concentration. The results revealed that the Ag–TiO2 hybrid NLs extended the light absorption spectrum toward the visible region and considerably enhanced the hydrophilicity of TiO2 NLs under visible light irradiation. The significant enhancement in the visible light hydrophilicity activity of TiO2 NLs under visible light irradiation can be ascribed to the generation of a new electronic state acting as an electron trap in TiO2 and responsible for narrowing the band gap of TiO2 and shifting its optical response from the ultraviolet to the visible light region.