Optical and structural properties of bare MoO3 nanobelt, ZnO nanoflakes, and MoO3/ ZnO nanocomposites: The effect of hydrothermal reaction times and molar ratios

In this paper, the successful synthesis of bare molybdenum oxide (MoO3) nanobelts using a one-step hydro thermal method without the use of surfactants is reported. Additionally, ZnO nanoflakes are synthesized through a green method, employing ginger extract, owing to the presence of phenolic compounds found in ginger, mainly gingerols, shogaols, and paradols. Furthermore, the fabrication of MoO3/ZnO nanocomposites using an uncomplicated and readily accessible ultrasonication method is presented. Also, the effects of hydrothermal reaction time (12, 24, and 36 h) and the molar ratio of MoO3 nanobelts (NBs) to ZnO nanoflakes (2:1, 1:1, and 1:2) are investigated on the properties of synthesized MoO3 nanostructures and MoO3/ZnO composites, respectively. The results declare that the optical and structural properties, morphology, and stability of the MoO3 are influenced by hydrothermal reaction time significantly and the uniform MoO3 nanobelts are obtained in a reaction time of 24 h. Also, the formation of nanocomposites with different ratios of MoO3 nanobelt and ZnO nanoflakes by ultrasonication leads to forming uniform distributions of ZnO nanoparticles on the surface of MoO3 structures. Indeed, the ultrasonication condition causes the transformation of the biphasic MoO3 structure to a single-phase MoO3 in the composites. Furthermore, the optical properties of MoO3 nanobelts including the reflection especially in the UV region, and also the bandgap energies of the NBs are affected by providing the nanocomposites, and the bandgap energies change from 2.94 eV (bare MoO3 nanobelts) to 3.18 eV (nanocomposites). The reasons for the phenomena are explained in the paper. These insights into the controlled synthesis of MoO3 nanostructures and MoO3/ZnO nanocomposites pave the way for potential applications in fields such as advanced sensors, optoelectronics, and energy-efficient devices.