Architectural tailoring of orthorhombic MoO.sub.3 nanostructures toward efficient NO.sub.2 gas sensing

In the present study, an architectural tailoring strategy was established to tune crystalline orthorhombic molybdenum trioxide ([alpha]-MoO.sub.3) to obtain nanostructures such as nanorods, dumbbell-shaped nanorods and hierarchical nanodisks for chemiresistive gas sensors. The different types of [alpha]-MoO.sub.3 nanostructures were synthesized by adopting controlled hydrothermal reaction conditions such as reaction time and temperature. The morphological variation of nanostructures revealed changes in crystalline parameters, such as size, micro-strain, shape, surface area, and porosity. The microstructural effects and shape of the [alpha]-MoO.sub.3 nanostructures were studied to determine their influence on the analytical characteristics of a gas sensor, the sensitivity, response time, and selectivity toward NO.sub.2 analyte gas. The high surface area of [alpha]-MoO.sub.3 nanorods showed a high sensitivity of 84% at an optimal operating temperature of 110 °C, with response and recovery times at 45 and 42 s, respectively, then dumbbell-shaped nanorods is reduced with 10% lower sensitivity than nanorods at 74% at a temperature of 130 °C. Nanodisks showed the least response compared to all the synthesized structures. All nanostructures of [alpha]-MoO.sub.3 exhibited good selectivity for the NO.sub.2 analytical gas with respect to interfering gases such as CO.sub.2, NH.sub.3, ethanol, methanol, and acetone and in addition, good stability and reproducibility have been observed.