Transparent graphene quantum dot/amorphous TiO2 nanocomposite sol as homogeneous-like photocatalyst

The transparent nanocomposite sol of graphene quantum dot and amorphous TiO2 (GQD/a-TiO2) was successfully synthesized and used as a homogeneous-like photocatalyst in degradation of rhodamine B (RhB). Analysis of GQD/a-TiO2 structure suggested that the existence of surface functional groups decorated on the GQD sheets played a vital role in anchoring a-TiO2 by chemical interaction and avoiding sol transformation during photocatalytic water treatment. The spectroscopic results and computational calculations indicated that the nanostructural interactions between GQD and a-TiO2 through Ti–O-C bonds had a significant impact on determining optical and electronic properties of the nanocomposite sol. It was found that GQD with smaller size provided the greater extent of interactions with a-TiO2 at nanoscopic level, resulting in narrowing of the band gap energy in GQD/a-TiO2 nanocomposite in comparison with a-TiO2. For photocatalytic study, the GQD/a-TiO2 sol catalyst could be applied for the degradation of RhB under indoor and outdoor natural light. The photocatalytic enhancement of the sol catalyst was considered as a result of the band gap narrowing and the synergistic effects of band attachment in the nanocomposite.