Bilayer Polyaniline–WO(3) Thin-Film Sensors Sensitive to NO(2)

[Image: see text] In this work, a novel bilayer polyaniline–WO(3) (PANI–WO(3)) thin film on the fluorine-doped tin oxide (FTO) glass substrate was prepared by hydrothermal synthesis and in situ chemical oxidative polymerization methods. Until now, no one has ever made attempts to use the PANI–WO(3) composite on the FTO glass substrate to detect NO(2) gas. The composite showed excellent sensing performance for NO(2) detection at an operation temperature of 50 °C and a detection limit of 2 ppm. With regard to the PANI–WO(3) hybrid, the response value for NO(2) at 30 ppm is 60.19 and is three times higher than that for pure WO(3) at 50 °C. Besides, the PANI–WO(3) hybrid had excellent stability. The improvement of gas sensing was assigned to the creation of p–n heterojunctions between p-type PANI and n-type WO(3), larger specific surface, increase of oxygen vacancies, and a wide conduction channel provided by PANI.