N, S co-doped graphene quantum dots-graphene-TiO2 nanotubes composite with enhanced photocatalytic activity.

N, S co-doped graphene quantum dots (N, S-GQDs) -reduced graphene oxide- (rGO) -TiO 2 nanotubes (TiO 2 NT) composites were prepared by a facile alkaline hydrothermal reaction and physical stirring process. The apparent rate constant of the N, S-GQDs+10%rGO + TiO 2 NT composite, exhibiting the highest photodegradation efficiency, is 1.8 times and 16.3 times higher than those of 10%rGO + TiO 2 NT and pure TiO 2 NT, respectively, for the degradation of methyl orange (MO) under visible light irradiation (λ > 400 nm). Our work could provide new insights into the fabrication of GQDs-semiconductor composites as high performance photocatalysts and broaden the range of doped GQDs widely used for environmental protection. [ABSTRACT FROM AUTHOR]