Antibacterial self-cleaning binary and ternary hybrid photocatalysts of titanium dioxide with silver and graphene

The bacterial sterilization of TiO2 photocatalysts for self-disinfected and hygienic surfaces and coatings was explored to enhance by incorporating silver and reduced graphene oxide layers. Binary Ag/TiO2 and ternary Ag/TiO2/rGO (reduced graphene oxide) nanohybrids were developed by a hydrothermally modified sol-gel method preceded by the synthesis of Ag nanospheres by polyol method using cetyltrimethylammonium bromide (CTAB) as the capping agent. The metallic state and crystalline nature of Ag in the hybrids were affirmed using XRD, TEM, and XPS analyzes. The developed nanohybrids were studied for their visible-light-induced photocatalytic self-cleaning behavior determined from photo-induced wettability and photodegradation of methylene blue dye. Ag/TiO2/rGO ternary hybrid showed excellent photocatalytic antibacterial properties towards Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus), under visible-light excitation. ~100% disinfection of bacterial environments (both E. coli and S. aureus) were achieved within 180 min of visible-light irradiation. Finally, a plausible mechanism for the visible-light-induced photocatalytic antibacterial behavior of the as-prepared binary and ternary hybrids of TiO2 is proposed. Surface plasmon resonance induced by visible-light excitation injects hot electrons from Ag nanoparticles to the conduction band of TiO2 with the simultaneous charge separation facilitated by graphene counterpart produces a high concentration of reactive oxygen species, which is accountable for the superior photocatalytic self-cleaning and the bacterial cell lysis by Ag/TiO2/rGO hybrid.