Facile synthesis of α-MoO3 nanorods with high sensitivity to CO and intrinsic sensing performance

Orthorhombic molybdenum trioxide (α-MoO3) nanorods with well-defined morphology and high crystalline have been synthesized by a facile and fast hydrothermal method under 85 °C for 1.5 h without employing surfactants or templates. The controlling of stirring time, thermostatic time and HNO3 amount is crucial for the growth of α-MoO3 nanorods. The morphology and structure of α-MoO3 were characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The obtained α-MoO3 nanorods as a novel sensing material exhibit high sensitivity, the highest response to 40 ppm CO is 239.6 at operating temperature of 292 °C. The intrinsic sensing performance arises from the non-stoichiometry of the α-MoO3 due to the presence of Mo5+ in MoO3 lattice, that is, the molecular formula of MoO3 should be expressed as MoO3 − x (x = 0.08), which has been confirmed by X-ray photoelectron spectroscopic (XPS) analysis and room temperature photoluminescence (PL). The sensing mechanism of α-MoO3 to CO was also discussed in terms of lattice oxygen in MoO3.