Effect of Au nanoparticle size on the gas-sensing performance of p-CuO nanowires

Networked p-CuO nanowires (NWs) were grown on a patterned electrode pad by the thermal oxidation of an electron-beam-deposited Cu layer. The Au nanoparticles (NPs) were then functionalized on CuO NWs by the heat treatment of an Au layer deposited by sputtering. The diameter of the functionalized Au NPs could be controlled in the range of 20-145 nm by changing the thickness of the deposited Au layers. The sensing properties of the Au-functionalized networked CuO NWs for representative oxidizing (NO2) and reducing (CO) gases were investigated. Au functionalization greatly enhanced the gas-sensing abilities of the CuO NWs. The CuO NWs showed the best sensing properties when they were functionalized with 60 nm-diameter Au NPs. This suggests that the size optimization of the metal NPs for functionalization is essential for obtaining the superior sensing properties of oxide NWs.