Effect of surfactants on photoluminescence properties of ZnO synthesized by hydrothermal method

Abstract

The effects of different surfactants on structure, morphology and PL properties of ZnO synthesized by hydrothermal method are investigated. SEM results show that the size and the morphology of ZnO can be effectively controlled by surfactants. Compared to other XRD results, the diffraction peak of ZnO in the presence of surfactant monoethanolamine (MEA) has better crystal quality, smaller FWHM and stronger intensity. Furthermore, the PL spectra of ZnO in the presence of sufactant MEA show an increase in the sharp UV emission band and the nearly visible broad emission band. Gaussian curve deconvolution for experimental PL spectrum of ZnO indicates that the enhancement of UV emission is due to the improvement on crystallinity and the mechanism of visible emission is ascribed to several intrinsic defects or hydroxyl groups on the surface of ZnO, which is in consistent with the FTIR results. The best PL properties of ZnO can be found in the presence of MEA (the molar ratio of MEA to Zn2+ is 1:1) with annealing temperature at 120 °C for 8 h annealing time. In conclusion, the introduction of surfactant MEA with both amino group and hydroxyl group in the synthesis of ZnO is beneficial to crystallinity and intrinsic defects on the surface of ZnO, which can enhance the PL properties.