Photocatalytic Reduction of Graphene Oxide Nanosheets on TiO₂ Thin Film for Photoinactivation of Bacteria in Solar Light Irradiation

Graphene oxide platelets synthesized by using a chemical exfoliation method were deposited on anatase TiO2 thin films. Postannealing of the graphene oxide/TiO2 thin films at 400 °C in air resulted in partial formation of a Ti−C bond between the platelets and their beneath thin film. By using atomic force microscopy and X-ray photoelectron spectroscopy analyses, UV−visible light-induced photocatalytic reduction of the graphene oxide platelets of the annealed graphene oxide/TiO2 thin films immersed in ethanol was studied for the different irradiation times. After 4 h of photocatalytic reduction, the vertical space between the platelets decreased from about 1.1 to less than 0.8 nm and the concentration of the C═O bond was reduced 85%, indicating effective reduction of the graphene oxide platelets to the graphene ones. The graphene oxide/TiO2 thin films reduced at different irradiation times were utilized as nanocomposite photocatalysts for degradation of E. coli bacteria in an aqueous solution under solar light irradiation. The photocatalytic reduction of the graphene oxide platelets for 4 h caused an improvement of the antibacterial activity of the TiO2 thin film by a factor of about 7.5. The reduced graphene oxide platelets were chemically stable after photoinactivation of the bacteria.