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

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.