Novel ZnSQDs-SnO2/g-C3N4 nanocomposite with enhanced photocatalytic performance for the degradation of different organic pollutants in aqueous suspension under visible light

Abstract We report the synthesis of ZnS quantum dots (ZnSQDs)–SnO2/graphitic C3N4 (g-C3N4) ternary nanocomposites with different mass ratios via solid-state calcination of a mixture of 10 wt% ZnSQDs–SnO2 and g-C3N4. The proposed solid-state procedure does not require any solvent and offers a general route to synthesize composite materials on a large scale. The synthesized products were carefully characterized by traditional analytical techniques such as Fourier transform IR spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of the nanocomposites was assessed by our studying the degradation of two different chromophoric dyes (rhodamine B and methylene blue) and a colorless pollutant (paracetamol) in aqueous suspension under visible light in the presence of atmospheric oxygen. Among the series of synthesized samples, 7 wt% ZnSQDs–SnO2/g-C3N4 showed significantly improved photocatalytic performance in comparison with the other photocatalysts. In addition, adsorption of dyes onto the surface of the synthesized nanocomposite was studied with different catalyst amounts and time intervals. Moreover, the synthesized material also mineralizes paracetamol, which was measured in terms of depletion of total organic carbon content as a function of time. The remarkable increased photocatalytic efficiency of the synthesized materials could be related to the synergistic interaction between ZnSQDs, SnO2, and g-C3N4 leading to photoseparated electron and hole pairs. The main reactive species involved in the degradation process were determined by our performing quenching experiments with electron donors and acceptors, and a possible mechanistic pathway for the degradation process is proposed.