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

Abstract

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.