UV enhanced SnO2/TiO2 nanorods-based flexible room temperature sensor by tuning interfacial chemistry and microstructure

Abstract

The high working temperature of metal oxide semiconductors hinders its application in flexible sensing devices. In this paper, a UV-activated flexible sensor operating at room temperature (RT, 25℃) is first reported based on SnO₂ nanoparticles embedded in photo-catalytic TiO₂ nanorods matrix. The UV-irradiated SnO₂/TiO₂ sensor exhibits excellent selectivity (109 ppm, 37 %) to CH₃COOH and reduced response/recovery time (12 s/41 s). The excellent RT flexible sensing properties are attributed to the synergistic action of UV-365 nm irradiation, the hetero-embedded microstructure and innovative terpineol binder. UV irradiation generates substantial $e_{h\upsilon }^{-}$-$h_{h\upsilon }^{+}$ pairs, which serve as active sites to promote the chemisorption and redox reactions. Additional activation energy helps to improve adsorption/desorption kinetics. The heterojunction provides abundant channels, facilitating the separation and transfer of photogenerated carriers. The effect of relative humidity (RH) and temperature variations around RT on the sensor response towards CH₃COOH are investigated. Under low-RH (35 %-45 %) and high-RH conditions (above 45 %), 1 % RH change has the same effect on the sensor response than 7.2 ppm and 59.4 ppm CH₃COOH, respectively. 1°C temperature change exhibits the same effect than 17.9 ppm CH₃COOH. Such a noise effect is by far not suitable for real-world applications. In addition, the response to 109 ppm CO reaches up to 89.5. Therefore, the sensor is seriously disturbed by CO and further research is needed. Above all, UV assistants, hetero-composites combining with innovative microstructure design are expected to be a collaborative enhancement strategy for MOSs-based RT flexible sensors.