Order−disorder interfaces in a graphitic carbon nitride-nanoclay composite for improved photodynamic antibiotics

Abstract

Antibiotic-resistant microorganisms are a threat to human health. Despite efforts to treat bacterial and fungal infections with photodynamic therapy, it suffers from low light absorption and low singlet oxygen yield. Here, we observe order-disorder interfaces in graphitic carbon nitride (g-C3N4) modified by kaolinite nanoclay via polar interactions, decreasing the band gap of g-C3N4. The polar interactions originate from interactions between the basic amine surface moieties and hydrogen-bonding motifs of g-C3N4 and the hydroxyl groups on the nanoclay surface. Surface free energy theory demonstrates that the electron-acceptor displayed by the nanoclay surface could form a couple with g-C3N4 due to its nucleophilic property. The polar interactions accelerate electron transfer, and the nanoclay surface functions as an electron sink due to its polar surface and free energy. This promotes spin-orbit coupling and intersystem crossing resulting in a higher singlet oxygen yield, even in the dark. The graphitic carbon nitride-kaolinite composite showed improved and faster would healing in rat animal models.