Growth and Extension of One-Step Sol–Gel Derived Molybdenum Trioxide Nanorods via Controlling Citric Acid Decomposition Rate

A simple sol–gel solution route for the synthesis of α-phase molybdenum trioxide (α-MoO₃) nanorods is investigated in terms of growth mechanism with controlling the citric acid decomposition rate. The single-phase and single-crystal nanorod arrays of MoO₃ grown in random directions from a silica glass substrate had mean diameters and lengths of 10 and 500 nm, respectively, as determined through chemical analysis. The citric acid plays a critical role for the nanorods growth process from investigating the relative molar ratio of molybdate and citric acid in the precursor. Moreover, the dissociation timing of the citric acid, which was controlled by the other two synthesis parameters, i.e., sintering time and solvents, also greatly influences growth and phase transition of the MoO₃ nanorods, which was analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The synthesis parameters were optimized to design the length and density of the nanorod arrays. The longest nanorods can be obtained up to 600 nm using a dimethylacetamide solvent, a molar ratio of Mo:citric acid = 0.5:1.5, and sintering at 673 K for 15 min in an ambient atmosphere. Findings of the present study describe that the factors of the nanorods’ growth and phase changing are deeply correlated with disassemble steps of the Mo metal–citric acid complex in the sol–gel precursor solution, which may contribute to applying the material development in several electronic devices using MoO₃ nanostructures