PI-SiO<sub>2</sub>/NiI<sub>2</sub> colorimetric humidity sensor with fast response and recovery

Abstract

The organic-inorganic hybrid colorimetric humidity sensor which can obtain environmental humidity by electrical signals and color changes has broad application prospects in the field of humidity monitoring because of its high feature color discrimination, excellent stability, and simple preparation process. However, its long response-recovery time is generally not conducive to real-time humidity monitoring. In this paper, nanometer silica particles are doped into polyimide(PI)-nickel(II) iodide(NiI<sub>2</sub>) organic-inorganic hybrid materials to fabricate PI-SiO<sub>2</sub>/NiI<sub>2</sub> composite films and colorimetric humidity sensors. Then their surface morphologies and humidity sensing properties are studied. It is found that PI-SiO<sub>2</sub>/NiI<sub>2</sub> film possesses a honeycomb-like surface morphology, the humidity sensitivity of PI-SiO<sub>2</sub>/NiI<sub>2</sub> colorimetric humidity sensor is better than that of other NiI<sub>2</sub> based humidity sensors, its characteristic color is distinct in a range of 11%–97% RH humidity, and the humidity response time of the PI-SiO<sub>2</sub>/NiI<sub>2</sub> colorimetric humidity sensor is less than 1.5 s, and the recovery time is less than 18 s. The research result indicates that the doping of nanometer silica particles can effectively improve response-recovery properties of the organic-inorganic hybrid colorimetric humidity sensor, which is helpful in improving the performance of the sensor.