Gold-Nanoparticle-Functionalized In2O3 Nanowires as CO Gas Sensors with a Significant Enhancement in Response

We present the room-temperature sensing of gold nanoparticle (AuNP)-functionalized In2O3 nanowire field-effect transistor (NW-PIT) for low-concentration CO gas. AuNPs were functionalized onto In2O3 nanowires via a self-assembled monolayer of p-aminophenyltrimethoxysilane (APhS-SAM). The nanowires were mounted onto the Au electrodes with both ends in Schottky contacts. High sensor response toward low concentration of CO gas (200 ppb-5 ppm) at room temperature is achieved. The presence of AuNPs on the surface of In2O3 nanowire serves to enhance the CO oxidation due to a higher oxygen ion-chemisorption on the conductive AuNP surfaces. Detailed studies showed that the sensing capabilities were greatly enhanced in comparison to those of bare nanowires or low coverage of Au NP-decorated nanowires. When the sensor is exposed to CO, the CO molecules interact with the preadsorbed oxygen ions on the AuNP surface. The CO oxidation on the AuNPs leads to the transfer of electrons into the semiconducting In2O3 nanowires and this is reflected as the change in conductance of the NW-FET sensor. This work provides a promising approach for fabricating nanowire devices with excellent sensing capabilities at room temperature.