Effect of Hydrothermal Temperature on the Morphology and Structure of Synthesized MoS₂ Nanostructures

Abstract

The MoS₂ nanostructures with different morphologies were synthesized by a facile hydrothermal method using precursors of ammonium molybdate ((NH₄)₆Mo₇O₂₄·4H₂O), thiourea (CH₄N₂S) and hydroxylammonium chloride (NH₂OH·HCl). As-prepared MoS₂ samples with different growth temperatures of 160, 180, and 200 °C were characterized by Raman spectroscopy, field emission scanning electron microscopy (FESEM) and x-ray powder diffraction (XRD). Raman data of all samples showed the two active modes at about 380 cm⁻¹ and 406 cm⁻¹, which were corresponding to in-plane vibration of Mo and S atoms as well as to out-of-plane vibration of S atoms of MoS₂ nanostructures. XRD results also revealed characteristic diffraction peaks of the MoS₂ for all samples grown at different temperatures. However, the XRD pattern of the MoS₂ grown at 200 °C exhibited a more pronounced peak at approximately 12.1°, corresponding to the diffracted peak of (002) lattice plane of MoS₂. It implied that the MoS₂ nanostructures synthesized at 200 °C showed a better crystallinity compared to the rest. The findings indicated that reaction temperature has significant effects on the morphology and crystal structure of the as-prepared products. It was found that the optimal growth temperature was 200 °C. Under this condition, the nanostructures are about more than 100 nm in length and 10 nm in thickness.