Bi-functional photocatalytic heterostructures combining titania thin films with carbon quantum dots (C-QDs/TiO2) for effective elimination of water pollutants

In this study, carbon quantum dots (C-QDs), prepared via hydrothermal-microwave procedures, were successfully combined with nanostructured titania (TiO 2 ). The photocatalytic oxidation/reduction activity of the C-QDs/TiO 2 composite films was evaluated in the decomposition of organic-inorganic contaminants from aqueous solutions under UV illumination. Physicochemical characterizations were applied to investigate the crystal structure of the carbon quantum dots and the composites. It was found that the prepared C-QDs/TiO 2 composites had great contribution to the photocatalytic reduction of hexavalent chromium (Cr +6 ) species and 4-Nitrophenol (PNP) as well as to the photocatalytic oxidation of methylene blue (MB) and Rhodamine B (RhB) dyes. The mechanism of the photocatalytic reaction was studied with trapping experiments, revealing that the electron (e − ) radical species were powerfully supported for the photocatalytic reduction of Cr +6 and PNP and the holes ( h + ) are the main active species for the photocatalytic oxidation reactions.