Photocatalysis aided antibacterial properties of a green graphitic carbon-Cu2O-Ag2O composite: Towards an active non-persistent disinfectant

A novel green graphitic carbon (GGC)-supported Cu2O-Ag2O composite has been successfully synthesized via a facile co-precipitation technique. Its photocatalysis-aided antibacterial activity was evaluated under lowintensity light-emitting diode irradiation. The GGC not only served as an adsorbent matrix but also helped in restricting the rapid recombination of the electron-hole pairs, resulting in 100 % inactivation of 2.3 x 103 CFU mL-1 Escherichia coli (E. coli) by the GGC-Cu2O-Ag2O composite within 15 min. In comparison to the composite, pristine GGC and Cu2O-Ag2O resulted in 13.8 and 61.5 % inactivation efficiency, respectively. Under optimal photo-chemical conditions (i.e., light wavelength: 440 to 625 nm; light intensity: 950 W m- 2; pH: 6.4; catalyst dosage: 1 g L-1), 6 x 107 CFU mL-1 of E. coli and Enterococcus faecalis were completely inactivated within 45 min and 60 min of irradiation, respectively. The addition of scavengers decreased E. coli inactivation efficiency from 100 % to 61 % implying that holes are the main reactive oxygen species (ROS). The scanning electron micrographs depict prominent ROS-induced morphological changes in the bacterial cells. Further, there was no regrowth of bacteria via photoreactivation and the dark repair process. Moreover, the composite exhibited excellent stability as well as adequate inactivation activity even after three consecutive reuse cycles. The remnants of the composite after exhaustion are likely to be naturally sequestrated without any transport potential and persistence.

Automated summary

A novel green graphitic carbon (GGC)-supported Cu2O-Ag2O composite was synthesized and showed excellent photocatalysis-aided antibacterial activity. Under optimal photo-chemical conditions, the composite completely inactivated Escherichia coli and Enterococcus faecalis within 45 to 60 minutes of irradiation. Holes were identified as the main reactive oxygen species (ROS) responsible for the antibacterial activity.