New insights into the controlled growth of hierarchical MoS2 nanospheres

Abstract

Hierarchical three-dimensional (3D) molybdenum disulfide (MoS2) nanospheres with diameter of about 1 μm have been successfully synthesized via a facile hydrothermal process by controlling the concentration of sulfur and molybdenum sources. The results show that the MoS2 nanospheres are self-assembled by numerous nanosheets, and the concentration of reactants plays a key role in the formation of the hierarchical MoS2 nanospheres. Specifically, the thickness of the nanosheets decreases gradually with the increasing concentration of reactants within certain limits. In addition, the possible mechanism of MoS2 nanospheres formation is proposed through analyzing the experimental results. Firstly, a fast nucleation of amorphous MoS2 particles occurs in the hydrothermal process by the oxidation–reduction reaction. Subsequently, the MoS2 nanoparticles start to spontaneously aggregate into MoS2 nanosheets according to their crystal growth habit. In the case of the appropriate concentration of reactants, the nanosheets are self-oriented and assembled by degrees to form the nanospheres driven by reducing surface energy. Finally, well-defined MoS2 nanospheres are formed through the Ostwald ripening process. The research will open a window to prepare novel hierarchical 3D MoS2 assembled by low dimensional nanoscale building blocks and the analysis of mechanism can also be used to discuss other transition-metal sulfides.