Investigation of structural and optical properties of molybdenum disulfide flakes/polyvinylidene fluoride nanocomposites

There is a growing potential use of molybdenum disulfide (MoS2) nanosheets loaded in polyvinylidene fluoride (MoS2/PVDF) in the fields of optoelectronics, ion batteries, and energy storage applications. The one-pot hydrothermal route was used to obtain exfoliated MoS2. The MoS2 nanoflakes were used to obtain MoS2/PVDF nanocomposite films by the solution casting process. The weight percent of MoS2 were 0, 0.1, 0.3, 0.5, 1, 3, 5, 10, and 20 wt% of the total weight of PVDF in the nanocomposite films. After annealing of the PVDF and MoS2/PVDF samples at 160 °C, the FTIR study showed many spectral changes including the spectral shift to high wavenumbers and the appearance of new peaks. These spectral changes indicate increasing of crystallinity, strong molecular bonds, and some crystal phase transition from γ to the β phase. Using Davis Mott's relation, the bandgap of MoS2/PVDF nanocomposites before and after annealing was determined. As the concentrations of MoS2 increase, the values of the optical bandgap decrease from 5.72 to 1.83 eV. Annealing the MoS2/PVDF nanocomposite at 160 °C resulted a remarkable decrease in the values of the bandgap energies from 5.64 to 1.16 eV. Tuning the bandgap energy could be achieved by a polynomial fitting to the experimental results. The X-ray diffraction (XRD) showed that PVDF/MoS2 nanocomposite films are amorphous, upon annealing at 160 °C partial crystallization occurred; however, the incorporation of MoS2/PVDF obstructs the crystallization of the MoS2/PVDF nanocomposite films.