High sensitivity and low hysteresis of humidity sensor based on imidazole derivative

The imidazole derivative 2–(4, 5–Diphenyl–1H–Imidazole–2–yl)phenol was deposited between the Ag-electrodes via drop-casting method to fabricate the humidity sensor. The rectangular-shaped flakes of various shapes and sizes along with voids, pores, and pore-channels have been observed in surface morphology of the deposited material. The water molecules (H₂O) interact with NH and N-sites in the central ring of the compound and functional group OH at ortho-position. The dielectric constant of the materials is around 1.4, which is slightly lower than our previously published value of 1.6. Capacitive and resistive behaviors of the device were checked at two different frequencies (1 kHz and 10 kHz) for different humidity levels. In the applied frequency range (1–10 kHz), with the humidity range of 45-95% RH, the capacitance of the sensor was improved from 10.1–378 pF, and from 7.43–16.48 pF, respectively. The sensor’s response and recovery time were 34 seconds and 6 seconds, respectively. The goodness of fit, R², value was 0.99 which is close to unity for physisorbed layers. The sensor showed low hysteresis and has good sensitivity in comparison with the reported devices based on other materials.