Synthesis and characterization of Zinc(II) bis(dithiocarbamate) humidity sensors

Zinc(II) bis(dithiocarbamate), hereafter ZnBz, material has been synthesized and used to fabricate humidity sensor. Structure of the ZnBZ compound was confirmed using the FT-IR, ^IH NMR, and ¹³C NMR spectroscopy techniques. The whitish color solution of ZnBz materials was deposited between the Ag-electrodes via drop-casting technique. The surface morphology of the material was studied using scanning electron microscopy (SEM) technique. The SEM images show that the thin film surface of the material possessed petals and hexagonal plates along with pores and pore-channels. The fabricated sensor was checked at different frequencies. The capacitive, resistive, and hysteric behavior of the sensor was studied at different humidity levels and different applied frequencies. Capacitance of the sensor was enhanced from 14 to 18 nF when humidity was changed from 30%RH to 90%RH keeping applied frequency constant at 120 Hz. However, at 1 kHz, the capacitance was increased from 145 to 355 pF in similar humidity range, while resistance was dropped from 3.5 MΩ to 282 kΩ at 120 Hz, and from 159 GΩ to 2.44 GΩ at applied frequency of 1 kHz. The response/recovery time was 81.7/60.7 s. Curve with two different slopes was obtained due to the switching from chemisorbed to physisorbed mode. The values of the goodness of fit, R², were 0.991 and 0.989 for chemisorbed and physisorbed layers. The sensor showed stable response over time. The maximum hysteresis, \({\text{H}}_{\text{max}}\) ${\text{H}}_{\text{max}}$ , values were 0.042% and 5.15% at applied frequencies of 120 Hz and 1 kHz, respectively.