Enhancing performances of a ZnO QDs-based humisensor by a simple LiCl loading: impedance spectroscopy and modeling investigations

Abstract

Uncapped ZnO QDs were used as a host to load LiCl salt at various contents for preparing humidity sensitive blends according to a straightforward method. The humidity sensitive characteristics of the prepared resistive-type sensors were investigated by impedance spectroscopy at different relative humidity levels. Compared to the pure ZnO QDs, an optimal LiCl content of 1.2 wt% improved all the humidity sensing performances. The impedance of the optimum sensor changed near four orders of magnitude over the whole humidity range, with a good linearity, negligible hysteresis, good long-term stability and short response and recovery times (11 and 4 s, respectively) at 100 Hz. Several considerations were taken into account including AFM and BET analyses, surface charge density, and numerical fitting results of the Cole–Cole impedance spectra to elucidate the major causes of sensor characteristics improvement.