Near-Ambient NO₂ Sensing with Vertical α‑MoO₃ Nanorods Synthesized by Pulsed Laser Deposition

Nitrogen dioxide (NO₂), which is a significant worldwide contaminant, requires accurate and immediate monitoring to safeguard and protect public health. Metal oxide semiconductors (MOS) have been rigorously employed for their chemiresistive gas sensing applications in the past; however, their high operating temperatures pose difficulty for practical implementation. In this study, an ultrathin vertical α-MoO₃ nanorod film is employed as the gas sensing material for sensitive detection of NO₂ under near-ambient conditions. We report a rare instance of an α-MoO₃-based gas sensor exhibiting a p-type response at near-room temperature. Pulsed laser deposition (PLD) at an elevated growth pressure of 8 Pascal and a substrate temperature of 550 °C was used to synthesize high-quality, vertically aligned ultrathin one-dimensional α-MoO₃ nanorods on silicon dioxide (SiO₂) substrates. These MoO₃ nanorods show high sensitivity to NO₂ with a response value of 19.7% for 50 ppm of NO₂ at 35 °C. Moreover, the sensor demonstrates an ultralow detection limit of 500 ppb at this temperature, underscoring its suitability for low-temperature, high-performance gas sensing applications and facilitating progress in environmental monitoring technology.