A low-temperature and mild solvothermal route to the synthesis of Wurtzite-type ZnS with single-crystalline nanoplate-like morphology

Wurtzite ZnS, a high-temperature polymorph of ZnS, was prepared by a novel low-temperature and mild solvothermal process over a temperature range of 160-200 degrees C. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high resolution transmission electron microscopy (HRTEM) analytic techniques were applied to characterize the composition and morphology of the products. The effects of solvent properties and reaction temperatures on the product purities and crystal structures were investigated. The solvent not only acts as a thermal conducting medium and extractant or active nucleophilic agent but also stabilizes the metastable wurtzite phase. As a result, the high-temperature wurtzite ZnS polymorph can be formed under low-temperature solvothermal conditions. TEM observations denote that the synthesized wurtzite ZnS consists of quasi-square or rectangle nanoplate-like morphologies with lateral dimensions ranging from 1 to 2 mu m. SAED and HRTEM confirm the single-crystalline nature of the nanoplates. A novel solvothermal extraction mechanism is proposed.