One-dimensional growth of hexagonal rods of metastable h-MoO3 using one-pot, rapid and environmentally benign supercritical fluid processing

Highlights: • Highly phase pure and crystalline h-MoO₃ microrods obtained by one-pot and environmentally benign supercritical fluid method. • h-MoO₃ microrods undergoes disintegration to α-MoO₃ thin nanorods when increasing the reaction time. • Optical band gap energy of the h-MoO₃ was found to be 2.91 eV. • Photoluminescence properties of h-MoO₃ microrods were discussed. A facile and one-pot supercritical fluid method was demonstrated for the synthesis of phase pure crystalline h-MoO₃ microrods within a short reaction time of 5 min at 400 °C. The formation of h-MoO₃ was confirmed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and Raman spectroscopic analysis. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) images clearly revealed the formation of hexagonal h-MoO₃ rods. Further, photoluminescence emission peaks corresponding to band to band transition was observed in the h-MoO₃ microrods. It was observed that when increasing the reaction time from 5 min to 30 min at 400 °C, h-MoO₃ microrods undergoes disintegration to α-MoO₃ thin nanorods. Interestingly, h-MoO₃ microrods were also formed in a reaction time of 30 min at 400 °C when reducing the volume of nitric acid from 1 mL to ∼0.5 mL. The short reaction time and simple synthetic strategy makes this method can be suitable for the synthesis of other semiconductor nanomaterials for diverse applications.