Humidity sensors using in situ synthesized sodium polystyrenesulfonate/ZnO nanocomposites

Thin film humidity sensors have been prepared using in situ synthesized inorganic/organic nanocomposites of sodium polystyrenesulfonate (NaPSS) and ZnO. Its humidity sensing characteristics and the sensing mechanism have been investigated by measuring the complex impedance spectra of the sensor at different humidities. The logarithm of the impedance of sensor based on composite film changes linearly by four-orders of magnitude over almost whole humidity range (11-97% RH). Furthermore, the sensor exhibits a quick response (absorption: 2 s, desorption: 2 s) and small hysteresis (less than 2% RH). The composite film shows better sensing properties than NaPSS film, such as better linearity, quicker response. Explanation to the improvement is attempted by taking into account of the composition and structure of the nanocomposites.