High-performance ZnO humidity sensor synthesized by coprecipitation with PVP as surfactant for human respiration detection

Abstract

A high-performance zinc oxide (ZnO)/polyvinylpyrrolidone (PVP) humidity sensor was prepared by simple coprecipitation method with PVP as surfactant. The coprecipitation method has low reaction temperature, little energy consumption and simple preparation, which is suitable for large-scale production. The PVP makes sample’s surface with more hydroxyl and oxygen vacancies than pure ZnO, which can absorb more water molecules and promote the decomposition of water molecules into H₃O⁺ to form effective ion conduction. When the molar ratio of PVP to ZnO is 1: 1, the ZnO/PVP humidity sensor has low hysteresis (∼4.2%), short response/recovery time (9/10 s), excellent stability and high sensitivity with more than 4 orders of magnitude in relative humidity (RH) range from 11% to 95%. Moreover, the ZnO/PVP humidity sensor can distinguish different respiratory states of human body, which has a potential in monitoring and prevention of respiratory diseases.

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