Development of a Novel Gas-Sensing Platform Based on a Network of Metal Oxide Nanowire Junctions Formed on a Suspended Carbon Nanomesh Backbone

Abstract

Junction networks made of longitudinally connected metal oxide nanowires (MOx NWs) have been widely utilized in resistive-type gas sensors because the potential barrier at the NW junctions leads to improved gas sensing performances. However, conventional MOx–NW-based gas sensors exhibit limited gas access to the sensing sites and reduced utilization of the entire NW surfaces because the NW networks are grown on the substrate. This study presents a novel gas sensor platform facilitating the formation of ZnO NW junction networks in a suspended architecture by growing ZnO NWs radially on a suspended carbon mesh backbone consisting of sub-micrometer-sized wires. NW networks were densely formed in the lateral and longitudinal directions of the ZnO NWs, forming additional longitudinally connected junctions in the voids of the carbon mesh. Therefore, target gases could efficiently access the sensing sites, including the junctions and the entire surface of the ZnO NWs. Thus, the present sensor, based on a suspended network of longitudinally connected NW junctions, exhibited enhanced gas response, sensitivity, and lower limit of detection compared to sensors consisting of only laterally connected NWs. In addition, complete sensor structures consisting of a suspended carbon mesh backbone and ZnO NWs could be prepared using only batch fabrication processes such as carbon microelectromechanical systems and hydrothermal synthesis, allowing cost-effective sensor fabrication.

Gas-Sensing Properties and Mechanisms of 3D Networks Composed of ZnO Tetrapod Micro-Nano Structures at Room Temperature

“…When exposed to reducing gases, the reaction between the gas and adsorbed oxygen species releases electrons that return to the sensor surface, resulting in a reduction in the EDL width and a decrease in sensor resistance. Conversely, exposure to oxidizing gases increases the EDL width and leads to an increase in sensor resistance [ 22 , 23 ]. However, in our study, the resistance of the sample increased upon exposure to ethanol or oxygen.…”

“…As one of the most critical n-type semiconductors with high electron mobility, ZnO has been widely utilized in gas-sensing applications since the 1960s [ 21 ]. In recent decades, with the advancement of nanoscience and nanotechnology, a diverse range of nano-ZnO gas sensors have been fabricated, including nanowires [ 22 ], nanorods [ 23 ], nanotubes [ 24 ], nanosheets [ 25 ], nanoflowers [ 26 ], and so on. Typically, these sensors function within the temperature range of 150–500 °C or can be operated at room temperature with auxiliary means such as UV light irradiation [ 27 , 28 , 29 ].…”

Batch Nanofabrication of Suspended Single 1D Nanoheaters for Ultralow‐Power Metal Oxide Semiconductor‐Based Gas Sensors

“…These circumferentially distributed ZnO NWs made the sensing sites more accessible to gas molecules, and the suspended architecture facilitated efficient gas transfer from the bulk, allowing highly sensitive gas sensing. [48,49] Ahead of the ZnO NW integration step, the sensor electrode leads (Figure 6a and Figure S3, Supporting Information) for measuring the ZnO NW network resistance were patterned at both ends of the NW network. The ZnO NW network was well-coated on the sensor electrode lead, as indicated by the blue dotted box in Figure 6e.…”

Highly Efficient MoS2/CsxWO3 Nanocomposite Hydrogen Gas Sensors

“…A polluted atmosphere endangers the health of living organisms. It comprises various gases that exist in nature and those released from industries (Masteghin et al, 2019;Pisarkiewicz et al, 2020;Duc et al, 2020;Kim et al, 2021). These odorless, tasteless, colorless gases are toxic when they exceed the safe limits (Ha et al, 2018;Miglietta et al, 2020;Pisarkiewicz et al, 2020).…”