High Sensitivity, Humidity-Independent Ethanol Gas Sensors Based on PFDS-ZnSnO₃ Hollow Microsphere

Abstract

Breath analysis using gas sensors to detect disease-related exhaled breath for diagnosing human health has huge application potential. However, the humidity changing in both the surrounding environment and exhaled breath have great damage to the actual sensing results, so the humidity dependence of gas sensor is a major obstacle to breath analysis applications. Here, 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PFDS) is used to hydrophobic the prepared ZnSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> sensor to obtain a high sensitivity and humidity-independent ethanol sensor for breath analysis. The ethanol sensing characteristics of PFDS-treated sensors were studied under dry and high humidity (RH (relative humidity) = 80%) conditions. The response value of pure ZnSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> sensor to ethanol dropped from 33.7 to 3.2 as the condition change form dry to 80% RH. On the contrary, the response of the 3h PFDS-ZnSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> sensor to 100 ppm ethanol was 7.5 under 80% RH, which was basically the same as the response (7.3) under dry conditions, indicating the same sensing behavior under dry and humidity conditions without being affected by moisture. In addition, the PFDS-ZnSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> sensors ignore the interference of other volatile gases under dry and humid conditions, while maintaining excellent selectivity to ethanol. The humidity-independent properties are attributed to the fact that PFDS with low-energy groups make the sensor surface hydrophobic, thus the material resists the contact of water molecules with the sensor and competition with ethanol in the gas response. Therefore, regardless of humidity fluctuations, the sensor shows great practicability in detecting ethanol and could be used for medical breath analysis.