Sol–gel synthesis of a novel melon–SiO2 nanocomposite with photocatalytic activity

A simple sol–gel method, starting from thiourea, was used to prepare a SiO2-based nanocomposite that absorbs across the visible region after calcination at 500 °C. The UV–visible spectrum, elemental (N) analysis, thermogravimetric data, and FTIR indicate that the coloration derives from an overlayer of melon, a thermally-stable precursor of graphitic carbon nitride. XPS and solid-state 29Si NMR showed no evidence for surface or bulk doping by N or S. The nanocomposite has unexpectedly high photocatalytic activity in methylene blue degradation under visible light and is probably due to a synergism between melon and SiO2.