Effect of Addition of Surfactant to the Surface Hydrophilicity and Photocatalytic Activity of Immobilized Nano-TiO₂ Thin Films

Abstract

We study the effect of adding cetrimonium bromide (CTAB) as a surfactant to titanium dioxide (TiO₂) solution for immobilizing TiO₂ on glass substrates. The thin films are deposited by the dip-coating technique. After dipping into the TiO₂ sol, the films are calcined and a pure anatase crystal phase is obtained. The thickness of the thin film is changed by varying the number of the dip-and-calcine cycles. The prepared films are characterized using FE-SEM, TG-DTA, and XRD, and samples’ photocatalytic performances are tested with regard to the degradation of methylene blue dye. Aside from the photocatalytic performance, the photoinduced hydrophilicity of thin TiO₂ films surface is also studied.
Characterization results show that the addition of surfactant gives rise to characteristic patterns on the surface of the TiO₂ thin film, which also affects the photocatalytic activity. The addition of CTAB to the TiO₂ dipping solution has a negative effect because the calcination temperature is not sufficiently high to burn all the surfactants off. As for surface wettability, the addition of surfactant has a positive effect on the photoinduced surface hydrophilicity of the TiO₂ films under UV light.