Inactivation of antibiotic resistance gene by ternary nanocomposites of carbon nitride, reduced graphene oxide and iron oxide under visible light

Antibiotic resistance gene (ARG) should be eliminated during wastewater treatment to prohibit the rapid growth and colonization of antibiotic resistant bacteria (ARB) in different waterbodies. With an aim to do so, we have synthesized ternary nanocomposites of graphitic carbon nitride, reduced graphene oxide and iron oxide as visible light photocatalysts. The materials structures have been confirmed by XPS, FTIR, PL spectroscopy, and electron microscopy. The photocatalytic measurements confirmed that the composites can be activated by visible light. Two types of commercially available plasmid DNAs containing ARGs, pUC 18 (2686 bp) and pBR 322 (4361 bp) were successfully inactivated and consequently fragmented by the nanocomposite in presence of hydrogen peroxide and under visible light. The performance of nanocomposite was proven to be better than that of pure carbon nitride. Agarose gel electrophoresis confirmed that supercoiled plasmid DNAs were first converted to single stranded relaxed circular forms followed by their complete fragmentation. The photocatalytic inactivation of plasmids may be attributed to the photocatalytic activity of carbon nitride alone, relaxation of photogenerated charge carriers by reduced graphene oxide, quenching of electron-hole pairs and generation of additional hydroxyl radicals by hydrogen peroxide, photo-Fenton activity by iron oxide in presence of hydrogen peroxide and additional photocatalytic activity of iron oxide alone.