Investigation of the gas-sensing performance of CuO sensors functionalized with different stabilized Au nanoparticles

Abstract. In this work, which was presented at the Eurosensors 2024 conference (Maier et al., 2024a), we present the development of chemoresistive nanosensors based on ultrathin CuO/Cu2O films, fabricated through a two-step process involving thermal evaporation and subsequent oxidation on Si3N4-based micro-hotplate chips. The semiconducting metal oxide (SMOX) gas sensors are tested against various target gases like carbon monoxide (CO), carbon dioxide (CO2), and a mixture of hydrocarbons (HCMix). The CuO/Cu2O films are functionalized with sodium citrate and also with synthesized Au nanoparticles (Au NPs), which are stabilized with different types of ligands, namely, α-methoxypoly(ethylene glycol)-ω-(11-mercaptoundecanoate) (PEG–MUA), 3-mercaptopropionic acid (MPA), and citrate. While the Au NPs clearly increase the sensor response, in particular for CO2 and HCMix, we have figured out that the ligands have a significant impact on the sensor performance. In order to gain further insight into the influence of the different ligands on the sensing performance, the surface was characterized by scanning electron microscopy (SEM), and the composition was determined by grazing incidence X-ray diffraction (GIXRD) measurement.