Effect of reaction temperature and reaction time on the structure and properties of MoS2 synthesized by hydrothermal method

In this study, molybdenum disulfide (MoS2) nanostructures were synthesized by a facile hydrothermal process, using ammonium heptamolybdate tetrahydrate ((NH4)(6)Mo7O24.4H(2)O) and thiourea (CH4N2S) as the reactants. The effects of experimental parameters including reaction temperatures and reaction times on the structure and morphology of MoS2 have primarily been investigated. The morphology, microstructure, chemical composition and optical properties of as-synthesized MoS2 were characterized using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Raman and Photoluminescence spectroscopy. The FESEM and TEM results indicate that depending on the reaction temperature, the three types of morphologies of MoS2 crystals could be obtained. Morphologies of MoS2 changed gradually from aggregated particles to flake-like structure, then finally to nanosheet morphology with increasing reaction temperature from 160 to 220 C-o. However, it was found that the reaction time contributed significantly to the restacking and refinement of MoS2 crystal structure, rather than affecting the morphology of the investigated samples. Both XRD and Raman investigations reveal that the as-synthesized MoS2 has a hexagonal phase structure (2H-MoS2). Interestingly, the as-prepared MoS2 nanosheets exhibit photoluminescence in the visible range with the emitted photon energy of similar to 1.81 and similar to 1.95 eV, these properties make MoS2 a promising candidate as the material of choice for next-generation optoelectronic and photonic devices.