Work

Humidity-modulated UV-activated room-temperature NO2 sensing in Al-doped ZnO/ZnAl2O4 heterojunctions

Year: 2026

Type: article

Abstract: Room-temperature gas sensors are essential for low-power and distributed environmental monitoring, but conventional metal-oxide sensors often suffer from limited surface reactivity and environmental instability under ambient conditions. Herein, porous ZnO sheets and Al-doped ZnO/ZnAl₂O₄ nanocomposites were synthesized via a hydrothermal route followed by thermal treatment and evaluated as UV-activated NO₂ sensors at room temperature. Structural and spectroscopic analyses confirmed that Al incorporation induced lattice distortion, oxygen-vacancy-related defect formation, and partial ZnAl₂O₄ interfacial formation within the porous ZnO architecture, providing a distinct approach compared with conventional UV-activated ZnO sensors that mainly rely on photoinduced carrier generation. Under 254 nm UV illumination, the optimized ZAO-2 sensor exhibited a high response toward NO₂, with an R g /R a value of 35.45 at 10 ppm. The sensor also maintained concentration-dependent NO₂ detection over a controlled humidity range of 0–90% RH, with 60% RH providing the most favorable response among the tested conditions. These results suggest that Al-induced defect states, UV-generated carriers, and moderate humidity are likely associated with enhanced NO₂ adsorption and charge modulation under photoactivated conditions, whereas excessive water adsorption may interfere with gas adsorption and charge transport. This study highlights humidity as an important operational parameter for photoactivated room-temperature NO₂ sensing.

Source: Sensors and Actuators B Chemical

DOI: 10.1016/j.snb.2026.140655