Size- and shape-controlled synthesis of ZnIn2S4 nanocrystals with high photocatalytic performance

Abstract

A facile route for synthesizing size- and shape-controlled ternary hexagonal ZnIn₂S₄ nanocrystals with narrow size distributions is developed using oleylamine as the ligand and noncoordinating octadecene as the solvent. Tunable sizes from 2.1 nm to 9.2 nm of the ZnIn₂S₄ nanocrystals are achieved through manipulation of reaction temperatures. Furthermore, the obtained ZnIn₂S₄ presents a nanoplate structure by replacing the sulfur powder with thiourea as the sulfur source. Optical measurements of the ZnIn₂S₄ nanocrystals demonstrate that their optical properties are related to the sizes of the products. The band gap energy varies from 3.28 to 2.35 eV, corresponding to the size from 2.1 nm to 9.2 nm. Compared with the bulk material, the blue-shift of the absorption spectra is mainly due to the size-dependent quantum confined effect. Photodegradation investigation demonstrates that the annealed ZnIn₂S₄ nanocrystals reveal higher photocatalytic activity for degradation of methylene orange (MO) solution in the visible region than the annealed ZnIn₂S₄ nanoplates and unannealed ZnIn₂S₄ nanocrystals.