CO Gas Sensor Properties of Cu@CuO Core–Shell Nanoparticles Based on Localized Surface Plasmon Resonance

Hexagonal array of Cu@CuO core–shell nanoparticles (NPs) on the a-C:H thin film was prepared by codeposition of RF-sputtering and RF-PECVD. The trace of hexagonal NPs supperlattice was recognized by AFM image and XRD result. On the basis of localized surface plasmon resonance (LSPR) of core–shell NPs, the prepared array detected a low flow rate of CO gas at room temperature. XPS results indicate that the surface of Cu@CuO core–shell NPs have no chemical reaction with CO molecule. The physical absorption of CO molecule on the surface of Cu@CuO core–shell NPs increases the LSPR absorbance and causes a red shift in LSPR wavelength. These experimental results are in agreement with Mie theory studying provided that CO absorption on the core–shell increases the dielectric coefficient of the shell. The prepared Cu@CuO core–shell NPs show an average shift of 10–2 nm per molecule absorption, which can lead to detection of a single CO molecule per NP.