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Accurate detection of nitric oxide (NO) at parts-per-billion (ppb) levels is critical due to its adverse effects on human health, even at trace concentrations. This study presents the design and evaluation of Co 3 O 4 -loaded NiTiO 3 nanostructures for ultra-low concentration NO sensing. The nanostructures were synthesized via microwave-assisted hydrothermal method, yielding a hierarchical architecture of Co 3 O 4 nanoflowers uniformly distributed on NiTiO 3 rods. The optimized 2 wt% Co 3 O 4 /NiTiO 3 sensor displayed high sensitivity to NO in the 5–100 ppb range, at an optimal operating temperature of 200 °C, with a low detection limit (LoD) of ∼0.22 ppb, and rapid response/recovery times. The sensor displayed a remarkable stability over 90 days with only ∼15 % deviation in response and demonstrated robust performance under humid conditions (10–75 % RH). NiTiO 3 serves as a chemically stable backbone of the sensor, offering a high-resistance baseline and abundant active sites for oxygen adsorption. Co 3 O 4 modification significantly enhanced gas response by forming p–n heterojunctions, reducing resistance, and facilitating charge transfer. Additionally, mixed valence Co 2+ /Co 3+ and Ti 3+ /Ti 4+ , along with increased oxygen vacancy concentration, significantly improved surface catalytic activity. These structural and electronic features synergistically promoted efficient NO oxidation, contributing to superior sensing performance.
Tshabalala et al. (Wed,) studied this question.