Rapid, controllable, one-pot and room-temperature aqueous synthesis of ZnO:Cu nanoparticles by pulsed UV laser and its application for photocatalytic degradation of methyl orange.

Zinc oxide (ZnO) and ZnO:Cu nanoparticles (NPs) were synthesized using a rapid, controllable, one-pot and room-temperature pulsed UV-laser assisted method. UV-laser irradiation was used as an effective energy source in order to gain better control over the NPs size and morphology in aqueous media. Parameters effective in laser assisted synthesis of NPs such as irradiation time and laser shot repetition rate were optimized. Photoluminescence (PL) spectra of ZnO NPs showed a broad emission with two trap state peaks located at 442 and 485 nm related to electronic transition from zinc interstitial level (IZn ) to zinc vacancy level (VZn ) and electronic transition from conduction band to the oxygen vacancy level (VO ), respectively. For ZnO:Cu NPs, trap state emissions disappeared completely and a copper (Cu)-related emission appeared. PL intensity of Cu-related emission increased with the increase in concentration of Cu2+ , so that for molar ratio of Cu:Zn 2%, optimal value of PL intensity was obtained. The photocatalytic activity of Cu-doped ZnO revealed 50 and 100% increasement than that of undoped NPs under UV and visible irradiation, respectively. The enhanced photocatalytic activity could be attributed to smaller crystal size, as well as creation of impurity acceptor levels (T2 ) inside the ZnO energy band gap.