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 (alpha-S-8). 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 alpha-S-8 (i.e., CNRGOS(8)), while the second structure was the other way around (i.e., RGOCNS(8)). Both structures exhibited antibacterial activity under visible-light irradiation. CNRGOS(8) showed stronger bacterial inactivation than RGOCNS(8) in aerobic conditions. However, RGOCNS(8) was more active than CNRGOS(8) 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.