From ZnS•en0.5 nanosheets to wurtzite ZnS nanorods under solvothermal conditions

We report here that near-monodispersed wurtzite phase ZnS nanorods can be synthesized with high yield via decomposing a sheet-like ZnS center dot en(0.5) (en = ethylenediamine) precursor in a mixed solution of oleic acid/ alcohol/hexadecylamine under mild solvothermal conditions. These as-prepared nanorods are an average of 25 nm in diameter and 300 nm in length. A high-resolution transmission electron microscope (HRTEM) image and fast Fourier transform (FIT) pattern demonstrated that these nanorods were highly single-crystalline and grown along the [001] direction. A series of electron microscopy characterization results suggests that the growth of the present ZnS nanorods is governed by a novel ligand-assisted solid-solution-solid (LSSS) growth mechanism. In this mechanism, 3-10 nm sized sphere-like wurtzite ZnS nanoparticles and a small quantity of wurtzite ZnS nanorods with small aspect ratio were initially generated as the decomposition products of a ZnS center dot en(0.5) sheet-like precursor in a solvothermal system. Then, the small sphere-like ZnS nanoparticles started to dissolve into the solution and grow onto the nanorods with a small aspect ratio via a process known as Ostwald ripening and gradually developed into longer wurtzite ZnS nanorods with the assistance of a mixed ligand system of hexadecylarnine and oleic acid. The effects of ligand, solution composition, and reaction time on the morphology of ZnS are investigated in detail. Photocatalytic experiments showed that the as-synthesized ZnS nanorods performed a high activity for degradation of fuchsine solution under UV irradiation.