Facile Liquid-Phase Synthesis of a High-Performance Cd-Doped ZnO-Quantum-Dot-Based Photocatalyst

Doping is an effective functional modification method for improving the optical, electrical, and magnetic properties of semiconductors. Here, Cd-doped wurtzite ZnO-quantum-dot (ZQ) zero-dimensional nanomaterials were successfully prepared via liquid-phase synthesis. The experimental results showed that Cd doping can effectively shorten the bandgap, where the optical bandgap range of Cd-doping photocatalysts were 3.31–3.36 eV; in particular, the Cd5-ZQ (Cd contents of 0.5 wt%) sample reduced the bandgap from 3.39 to 3.31 eV compared to that of pure ZQ. This is consistent with the experimental results, where the simulation calculation results indicated the bandgap reduced from 3.107 to 2.912 eV after introducing Cd. Photoluminescence spectroscopy results confirmed the Cd-ion dopants efficiently capture excited electrons and further prolongs the charge lifetime. The degradation of a methylene blue solution under simulated solar light irradiation revealed that the photocatalytic properties of Cd-ZQ nanomaterial with suitable dopant concentration (Cd content 0.5 wt%) was significantly better than those of pure ZQ. The underlying mechanism involves a synergistic effect, and a reasonable and convenient strategy for uprate performance is presented.