Acetoin is an important oxygen-containing volatile organic compound associated with food aroma and fermentation processes. In this work, a La₂O₂CO₃/La₂Sn₂O₇ composite was prepared as a chemiresistive sensing material for acetoin detection. The sensor exhibited a clear and measurable response toward 30 ppm acetoin at 250°C. A pronounced dependence of the sensing behavior on relative humidity was observed. At relative humidity below approximately 30%, the response to acetoin was weak, whereas a distinct sensing signal appeared when the relative humidity reached 30% or higher. In addition, the sensor maintained an obvious response to acetoin under a nitrogen atmosphere, and the response magnitude was higher than that measured in air under same conditions. The combined effects of humidity and background atmosphere indicate that water-related surface processes may play an important role in regulating acetoin adsorption and charge transfer. The enhanced response under nitrogen further suggests that oxygen-containing surface species and gas-phase oxygen may influence the sensing process. These findings reveal an unusual humidity-dependent acetoin sensing behavior of La₂O₂CO₃/La₂Sn₂O₇ composites and provide a basis for further investigation of their sensing mechanism.

gas sensor,acetoin,gas-sensing mechanism,heterojunction