Preparation of titania-reduced graphene oxide composite coatings with electro- and photosensitive properties

Smooth and optically transparent titania (TiO2) and TiO2-reduced graphene oxide (RGO) composite films were successfully prepared here. A nanocrystalline anatase suspension was initially prepared by combining the sol-gel process and hydrothermal treatment. Graphene oxide (GO) nanosheets were prepared following a route similar to the Hummers method. Glass slides were then dip-coated using mixtures of TiO2 and GO suspensions. The concentration of GO in the prepared coatings ranged from 1 to 5 wt%. The coated samples were air-dried, and then either calcined or irradiated with UVA light. It was observed that UVA light promoted the reduction of GO to RGO, which increased both the electrical conductivity and hydrophilicity of the composites. The heat treatment of as-prepared coatings also decreased the water contact angle (WCA) with its surface, which is related to the removal of organics residues, graphene burning, and the increase in surface energy. The superhydrophilicity of the prepared samples was investigated after keeping them in air for up to 60 days, followed by UVA illumination. It was also demonstrated that a hydrophilic behavior can be induced in the samples prepared here by applying a direct current (DC) voltage, which could allow their use as smart materials in several applications.

Automated summary

Smooth and optically transparent titania (TiO2) and TiO2-reduced graphene oxide (RGO) composite films were successfully prepared by combining sol-gel process and hydrothermal treatment. UVA light promoted the reduction of GO to RGO, increasing electrical conductivity and hydrophilicity. Heat treatment decreased water contact angle and increased surface energy by removing organics residues and burning graphene.