Highly selective and sensitive detection of trimethylamine using WO3 hollow spheres prepared by ultrasonic spray pyrolysis

WO3 hollow spheres were prepared by ultrasonic spray pyrolysis of a citric-acid-containing precursor solution, and their trimethylamine-sensing characteristics were investigated. The WO3 hollow spheres showed a high response to 5 ppm of trimethylamine (Ra/Rg = 56.9, Ra: resistance in air, Rg: resistance in gas) with low cross-responses to 5 ppm C2H5OH, CO, CH4, C3H8, H2, NH3, and NO2. The high gas response observed was explained by the effective electron depletion of small primary particles and the enhanced gas accessibility of hollow structures with thin and porous shells. The enhanced trimethylamine selectivity was discussed in terms of the interaction between basic analyte gas and acidic sensing materials.