Examination of Au/SnO2 core-shell architecture nanoparticle for low temperature gas sensing applications

Au/SnO2 core-shell structure nanoparticles (NPs) were synthesized using two methods, microwave and conventional precipitation. In both cases, the size of the Au core was 12–18 nm and the thickness of the SnO2 shell was 8–12 nm. The particle size of SnO2 synthesized using the microwave and precipitation method was 3–5 nm and 1–2 nm, respectively. Upon heating to 400–600 °C, both particles maintained their core-shell morphology but the smaller SnO2 particles prepared using the precipitation method were more sintered. The resistance changes in films of these particles were measured as a function of CO concentration. The Au/SnO2 particles prepared using the microwave method showed higher sensor response than those prepared using the precipitation method, even providing a significant signal at testing temperatures approaching ambient conditions, thereby affording a new class of material for gas sensing. Both sets of core-shell particles showed higher sensor response than the SnO2 nanoparticles. The role of the Au core as a catalyst in improving the adsorption and oxidation of CO gas is important for improving the low temperature response. In addition, the maintenance of the size of SnO2 in the microwave method during sintering contributed to the higher response towards CO sensing.