Abstract
Metal-oxide sensors, detect gas through the reaction of surface oxygen molecules with target gases, are promising for the detection of toxic pollutant gases, combustible gases, and organic vapors; however, their sensitivity, selectivity, and long-term stability limit practical applications. Porous structure for increasing surface area, adding catalyst, and altering the operation temperature are proposed for enhancing the sensitivity and selectivity. Although humidity can significantly affect the property and stability of the sensors, studies focusing on the long-term stability of gas sensors are scarce. To reduce the effects of humidity, 1H, 1H, 2H, 2H–perfluorooctyltriethoxysilane (PFOTS) was coated on a porous SnO2 film. The interconnected SnO2 nanowires improved the high surface area, and the PFOTS coating provided superhydrophobicity at water contact angle of 159°and perfect water vapor repellency inside E-SEM. The superhydrophobic porous morphology was maintained under relative humidity of 99% and operating temperature of 300 °C. The CO gas sensing of 5, 20, and 50 ppm were obtained with linearity at various humidity. Flame detection was also achieved with practical high humidity conditions. These results suggest the simple way for reliable sensing of nanostructured metal-oxide gas sensors with high sensitivity and long-term stability even in highly humid environments.
Highlights
Semiconducting metal-oxide gas sensors have been studied for their significant applications in security, industrial safety, automobiles, medical diagnosis, and environmental monitoring [1,2,3]
Because the porous SnO2 film was composed of nanowires and a large amount of open pore, COthe gasporous diffused into thecomposed film surface and reactedand with region on the surface
To improve the gas sensing and reduce the influence of humidity, the specific porous morphology of interconnected SnO2 nanowires is investigated for high surface area and a PFOTS coating on the surface is performed for water vapor repellency
Summary
Semiconducting metal-oxide gas sensors have been studied for their significant applications in security, industrial safety, automobiles, medical diagnosis, and environmental monitoring [1,2,3]. To develop appropriate nanostructures for gas sensors, several dry process methods have been reported, including sputtering, chemical svapor deposition, pulsed laser deposition, and thermal evaporation [11,12,13,14,15,16,17]. Several structures, such as nanodots, nanobelts, nanohairs, nanowires, nanotubes, and nanoribbons, are prepared and applied to gas sensing with enhanced high sensitivity and low detection limit [18,19,20,21,22,23]
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