Characterization and study of reduction and sulfurization processing in phase transition from molybdenum oxide (MoO2) to molybdenum disulfide (MoS2) chalcogenide semiconductor nanoparticles prepared by one-stage chemical reduction method

Abstract

In this research, molybdenum disulfide (MoS2) nanoparticles were prepared by chemical reduction method using MoO3 and thiourea as a precursor. The physical properties of the synthesized MoO2–MoS2 nanoparticles annealed at different temperatures of 200, 300, 750 °C have been investigated, before and after exposure to sulfur vapor. The nanostructure of nanoparticles has been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM) analyses and UV–Vis spectrophotometer. The X-ray diffraction analysis showed the formation of MoS2 single phase at annealing temperature of 750 °C in the presence of sulfur vapor. The Raman spectrum of the nanoparticles revealed that the formation of MoS2 at 750 °C after annealing in sulfur vapor. The values of band gap were obtained in the range of 3.64–3.17 eV and 3.47–1.95 eV for MoS2 nanoparticles before and after exposure to sulfur vapor, respectively. According to SEM images, the grain size decreases with increasing annealing temperature up to 750 °C. Also, nanoplate–nanoparticles of MoS2 are formed at annealing temperature of 200–750 °C. The TEM images of MoS2 nanoparticles at T a = 750 °C confirm that the nanoparticles have a homogeneous distribution with a hexagonal structure. The FTIR spectra of the MoS2 nanoparticles showed the peaks at about 467 cm−1 belong to the characteristic bands of Mo–S.