Abstract
Semiconducting metal oxides can detect low concentrations of NO2 and other toxic gases, which have been widely investigated in the field of gas sensors. However, most studies on the gas sensing properties of these materials are carried out at high temperatures. In this work, Hollow SnO2 nanofibers were successfully synthesized by electrospinning and calcination, followed by surface modification using ZnO to improve the sensitivity of the SnO2 nanofibers sensor to NO2 gas. The gas sensing behavior of SnO2/ZnO sensors was then investigated at room temperature (~20 °C). The results showed that SnO2/ZnO nanocomposites exhibited high sensitivity and selectivity to 0.5 ppm of NO2 gas with a response value of 336%, which was much higher than that of pure SnO2 (13%). In addition to the increase in the specific surface area of SnO2/ZnO-3 compared with pure SnO2, it also had a positive impact on the detection sensitivity. This increase was attributed to the heterojunction effect and the selective NO2 physisorption sensing mechanism of SnO2/ZnO nanocomposites. In addition, patterned electrodes of silver paste were printed on different flexible substrates, such as paper, polyethylene terephthalate and polydimethylsiloxane using a facile screen-printing process. Silver electrodes were integrated with SnO2/ZnO into a flexible wearable sensor array, which could detect 0.1 ppm NO2 gas after 10,000 bending cycles. The findings of this study therefore open a general approach for the fabrication of flexible devices for gas detection applications.
Highlights
Nitrogen dioxide (NO2 ), one of the most hazardous gases, poses a great threat to humans, animals, and plants [1,2,3]
The results revealed that the SnO2 /ZnO nanofibers coated on titanium/gold interdigital electrodes exhibited high sensitivity and selectivity to NO2 gas sensing at ppb level, and at a minimum detection limit of 0.1 ppm during testing
Low humidity causes the blockage of electrospinning needle, whereas high humidity makes it difficult to collect samples at the collector
Summary
Nitrogen dioxide (NO2 ), one of the most hazardous gases, poses a great threat to humans, animals, and plants [1,2,3]. The interest in semiconducting metal oxides has grown in recent years owing to their good performance in the optical, electronic and gas sensor fields. Semiconducting metal oxides such as SnO2 , ZnO, In2 O3 , TiO2 , and NiO have the advantages of good chemical stability, excellent sensitivity, low cost, and easy fabrication. These semiconductors have been widely investigated and applied in NO2 gas detection [6,7,8,9,10,11]
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