Bimetallic AgAu_alloy@ZnO core-shell nanoparticles for ultra-high detection of ethanol: Potential impact of alloy composition on sensing performance

The detection/sensing properties of chemiresistive gas sensors are greatly improved by catalytically triggered bimetallic alloyed nanoparticles, because of their synergistic effect. In this work, well-defined AgAu_alloy@ZnO core-shell nanoparticles are synthesized with the various compositions of Ag and Au. Alloying Au with Ag gave superior thermal stability to Ag, which favored gas sensing performance. As the amount of Ag within the AgAu_alloy core increased, the optimum working temperature was lowered to 300 ℃ with the dramatically enhanced ultra-high response of 1755 was obtained for Ag₇₀Au₃₀ @ZnO NPs sensor to 100 ppm ethanol. The outstanding sensing performance of AgAu_alloy@ZnO were endorsed to the improved the electronic and catalytic properties of AgAu_alloy core, aplenty chemisorbed oxygen on the surface of ZnO, unique core-shell structure that bring large active surface area and enhanced electron transfer process at the interface between core and shell. Ultraviolet photoelectron spectroscopy (UPS) analysis shows that with increasing Ag concentration, the work function (ϕ) decreases and the chemisorbed oxygen increases that brings wider depletion layer and Schottky barrier between the AgAu_alloy core and the ZnO shell, enhancing the gas sensing response. Our findings suggest that the incorporation of noble metal alloy-metal oxide semiconductor based core-shell nanostructures enhance the gas sensing performance with selectivity in the practical field of applications in environmental issues and human health monitoring.