Tunable NO gas sensing behavior of α-Fe2O3 nanoparticles: p–n transition mechanism based on the Langmuir model

Sensitive, selective and low-cost sensors for nitric oxide (NO) detection are significant due to its toxicity. This report investigates the tunable sensing behavior in chemiresistive NO sensors using α-Fe2O3 nanoparticles as sensing materials. The sensor exhibits a distinctive sensing characteristic with a reversible transition from p- to n-type sensing behavior, which is regulated by working temperature. The temperature-modulated (200–400 °C) and concentration-dependent (100–1000 ppm) p–n transition diagrams are constructed, while the gas sensing behaviors can be well described using a two-isotherm model based on Langmuir adsorption theory. Detailed reactions between NO and α-Fe2O3 at each temperature are proposed, and the corresponding activation energy is calculated. It is demonstrated that the p–n transition mechanism during NO detection is modulated by the dynamic variations in the α-Fe2O3–NO interaction. The p–n transition observed as a specific behavior in NO gas sensing can provide a novel approach to enhance the recognition capability for NO gas.