Metastable MnS crystallites through solvothermal synthesis

Metastable (beta and gamma) and stable (alpha) MnS crystallites were synthesized by solvothermal reaction in various solvents at 190-200 degreesC. In tetrahydrofuran and benzene, the metastable MnS crystallites can be obtained. In water, ammonia liquor, ethylenediamine, alpha -MnS, which is converted from the metastable phase, would be obtained. The low solubility of MnS is the crucial reason to stabilize the metastable phase with good yield. The metastable MnS crystallites were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The metastable gamma -MnS crystallites with rodlike morphology were found, and a unique "methane-like" four-branched rod cluster was characterized. The blue shift of the absorption edge indicates the quantum size effect of metastable MnS nanocrystallites.