Tuning the defects and luminescence of ZnO:(Er, Sm) nanoflakes for application in organic wastewater treatment

Abstract

A series of ZnO nanoflakes modified with rare earth ions of Er and Sm were prepared by a simple chemical solution deposition approach. It was found that the doping content of rare-earth ions was dominant for the defects in the nanoflakes and the ability of photocatalytic degradation for rhodamine B (RhB). The ZnO:(Er, Sm) nanoflakes exhibited a superior photocatalytic activity compared to undoped ZnO mainly due to the longer lifetime of photogenerated electrons-hole pairs in the process of photocatalytic reaction, and Zn0.98Sm0.01Er0.01O nanoflakes could degrade 96.5% RhB within 60 min under UV light irradiation. PL results provided a strong evidence for the existence of VO defect, which was also found to be responsive for the enhanced photocatalytic activity of ZnO:(Er, Sm) nanoflakes. And the peaks at 515 nm and 550 nm could be attributed to the transitions of $$^{2} H_{11/2} \to^{4} I_{15/2}$$ and $$^{4} S_{3/2} \to^{4} I_{15/2}$$ from Er3+ ions, indicating the realization of green luminescence.