Graphene and g-C3N4 nanosheets cowrapped elemental α-sulfur as a novel metal-free heterojunction photocatalyst for bacterial inactivation under visible-light.

A new class of metal-free heterojunction photocatalysts was prepared by wrapping reduced graphene oxide (RGO) and g-C3N4 (CN) sheets on crystals of cyclooctasulfur (α-S8). Two distinctive structures were fabricated by wrapping RGO and CN sheets in different orders. The first was RGO sheets sandwiched in heterojunction of CN sheets and α-S8 (i.e., CNRGOS8), while the second structure was the other way around (i.e., RGOCNS8). Both structures exhibited antibacterial activity under visible-light irradiation. CNRGOS8 showed stronger bacterial inactivation than RGOCNS8 in aerobic conditions. However, RGOCNS8 was more active than CNRGOS8 under anaerobic condition. A possible mechanism was proposed to explain the differences between photocatalytic oxidative inactivation and reductive inactivation. As a proof-of-concept, this work could offer new inroads into exploration and utilization of graphene sheets and g-C3N4 sheets cowrapped nanocomposites for environmental applications.