Dual Resistance and Impedance Investigation: Ultrasensitive and Stable Humidity Detection of Molybdenum Disulfide Nanosheet-Polyethylene Oxide Hybrids.

There is an imperative demand for real-time relative humidity (RH) discrimination with excellent sensitivity and robust operation stability over a broad RH range at room temperature (22 °C). Of diverse two-dimensional (2D) materials, p-type molybdenum disulfide (MoS2) as a typical gas-sensing candidate has been rarely harnessed for humidity detection due to tiny response and undesirable stability induced by the conversion from electron to proton conduction with increasing RH. To overcome these issues, MoS2-polyethylene oxide (PEO) inorganic-organic nanocomposites as the sensing layer were facilely prepared in this work. The results showed that the composition-optimized composite film sensor surpassed the isolated MoS2 counterpart in terms of repeatability, response, hysteresis, stability, and selectivity. Both DC-resistance and AC-impedance analyses unveiled different roles of MoS2 and PEO components within composites. MoS2 strengthened the film structure, while hydrophilic PEO enlarged the water-adsorption capacity and thus improved the response and detection reliability via water-triggered ionic conductivity. This work afforded a feasible strategy via inorganic-organic combination to distinguish trace RH and improved the operation stability of 2D material-based sensors, simultaneously demonstrating realistic monitoring applications of exhaled gas detection and distance variation of moisture-emitting objects.