Co-Sensitization of ZnCo2O4 Hierarchical Microspheres with MoO3 and Ag Nanoparticles for Chemiresistive Detection of Acetone

Recently, the detection of acetone by using a gas sensor fabricated with metal oxide semiconductors has stimulated intense research enthusiasm, owing to its promising application in the noninvasive diagnosis of diabetes by monitoring human exhaled breath. In this work, a potential acetone sensor was fabricated by comodification of the nanosheets-assembled ZnCo2O4 hierarchical microspheres (HMSs) with MoO3 and Ag nanoparticles (NPs). The ZnCo2O4 HMSs were synthesized via a solvothermal route and then sequentially modified with MoO3 and Ag NPs via immersion, calcination, and photoreduction routes. The results of gas sensing measurement indicated that after modification with MoO3 and Ag, a continuous improvement of acetone sensitivity was realized on the ZnCo2O4 sensor. At the optimal working temperature of 260 °C, the response of the best Ag/MoO3/ZnCo2O4 sensor to 50 ppm of acetone was 7.23, which was about 3.3 and 1.4 times higher than that of ZnCo2O4 and MoO3/ZnCo2O4, respectively. Apart from the higher response, the selectivity and response speed of the Ag/MoO3/ZnCo2O4 sensor were also improved. The results of density functional theory calculations showed that the enhanced absorbability of ZnCo2O4 for acetone after modification with MoO3 and Ag should be responsible for the improved acetone sensitivity and selectivity of the Ag/MoO3/ZnCo2O4 sensor.