ZnO core-triggered nitrogen-deficient carbonaceous g-C3N4 shell enhances the visible-light-driven disinfection

Abstract

• A solid-state synthesis of ZnO@g-C 3 N 4 core-shell nanocomposites is reported. • A ZnO-triggered nitrogen-deficient shell is formed up to 20 wt.% g-C 3 N 4 loading. • This shell imparts stability and enhanced photocatalytic efficacy to the core. • The 5 wt.% g-C 3 N 4 loading exhibits high valence band intensity and exciton lifetime. • This optimal catalyst displays high disinfection performance under visible light. We report a solid-state synthesis of ZnO@g-C 3 N 4 core-shell nanocomposites, in which melamine—a precursor of graphitic carbon nitride (g-C 3 N 4 )—is thermally decomposed over a pre-formed ZnO core. The thermolysis has led to the formation of a nitrogen-deficient carbonaceous shell over the ZnO core—reported for the first time—when the g-C 3 N 4 loading has been sequentially increased up to 20 wt.%. With a further increase in loading to 50 and 80 wt.%, the signature of the g-C 3 N 4 has been observed in the shell. The quantitative studies using TGA have revealed the excessive decomposition of melamine over the surface of ZnO, whilst the nitrogen-deficiency of the carbonaceous shell has been unearthed by the XPS studies. The core-shell nanocomposite with 5 wt.% g-C 3 N 4 loading has been found to possess enhanced photocatalytic performance towards methylene blue degradation and visible-light-driven water disinfection. The enhanced photocatalytic activity has been attributed to the thin carbonaceous shell imparting high valence band intensity and exciton lifetime to the ZnO core. The nanocomposites have been found to generate an excess of hydroxyl radicals in comparison to g-C 3 N 4 or ZnO. Furthermore, the toxicity studies performed with the fibroblast feeder cells have revealed the biocompatibility of the materials for practical applications.