A highly sensitive gas-sensing platform based on a metal-oxide nanowire forest grown on a suspended carbon nanowire fabricated at a wafer level

This paper presents a highly sensitive gas-sensing platform based on a ZnO nanowire (NW) forest circumferentially grown on a suspended single glassy carbon NW. The fabrication was carried out at a wafer level using only batch fabrication processes including carbon-microelectromechanical systems and the hydrothermal method. The suspended architecture and relatively high elastic modulus of the carbon nanowires facilitates selective functionalization on the suspended NW. The circumferentially distributed NW arrangement enhances the accessibility of gas molecule to the ZnO-NW sensing sites, thus facilitating highly sensitive gas sensing. The suspended architecture also enhances efficient mass transfer from the bulk. This novel suspended three-dimensional (3D) NW-based sensor configuration allows better NO2 gas sensing capabilities in terms of the limit of detection (9.45 ppb, S/N = 3), sensitivity (0.393 ppb−1), and linear sensing range (50-300 ppb) compared to the same type of ZnO-NW-based gas sensor fabricated in contact with the substrate.