Surface Modification of SnO ₂ Gas Sensors with WO ₃ for Temperature-Dependent Selective Detection of Ethanol and Acetone

Herein, we present a strategy for selective detection of volatile organic compounds (VOCs) by modulating the reaction pathways using SnO2-based gas sensors via loading with acidic WO3 as the receptor material. The neat SnO2 nanoparticles (NPs) were synthesized using hydrothermal treatment and calcination. Two methods were utilized to fabricate WO3–SnO2 NPs: the impregnation method and mechanical mixing. The sensing responses to various VOCs were significantly improved by finely dispersed WO3-loaded SnO2 compared to SnO2 with low-dispersed WO3. Crucially, the introduction of WO3 enhances the material’s surface acidity, which in turn changes the main reaction pathway of ethanol oxidation from dehydrogenation to dehydration. The interaction between WO3 and SnO2 NPs had a notable impact on sensor properties. WO3 loading enhanced the response to ethanol by altering the reaction pathway at 350 °C and demonstrated selective detection of acetone at 250 °C due to its receptor effect. These findings highlight the importance of material design in SnO2-based sensors, where acidic oxide receptors like WO3 effectively modulate the reaction pathway to enhance gas selectivity, offering valuable insights for developing selective gas sensors for medical diagnostics.