Hydrothermal Synthesis of Hierarchically Organized MoS2 and Formation of Films Based on It

The effect of hydrothermal synthesis parameters on the crystal structure and morphology of MoS2 particles has been shown. The results of synchronous thermal analysis showed that at the concentration of molybdenum cations of 0.05 mol/L, the increase in the duration of hydrothermal treatment leads to a decrease in the total mass loss (Δm), and the increase in c(Mo), on the contrary, results in a significant increase in the total Δm value. The dependence of the exo-effect maximum position, related to the MoS2 oxidation with the formation of MoO3, on the synthesis conditions has been determined. According to X-ray powder diffraction data, the 1T-MoS2 phase is formed at minimum c(Mo) and duration of heat treatment. Increasing the time duration leads to the transformation of 1T-phase into 2H-MoS2. With increasing c(Mo), the 2H-phase transforms to 1T-MoS2 and further to 1T/2H-MoS2. The transformation of MoS2 structure has been also analyzed by Raman spectroscopy. According to the results of scanning electron microscopy (SEM), all samples represent flower-like nanostructures consisting of twisted nanosheets. According to transmission electron microscopy data, individual nanosheets with a length of 50–500 nm are formed after delamination of molybdenum disulfide structures. The microstructure of the obtained MoS2 film has been studied by SEM and atomic force microscopy. Analysis of the film surface by Kelvin-probe force microscopy allows one to establish that the material has high electrical conductivity, and the work function value of the film surface has been calculated.