Fabrication and characterization of chitosan-CeO₂-CdO nanocomposite based impedimetric humidity sensors

Nanocomposites of chitosan and cerium oxide‑cadmium oxide (CeO₂-CdO) nanopowder were developed to fabricate impedimetric humidity sensors. The low temperature-stirring was used to synthesize CeO₂-CdO nanopowder. Average particle size of synthesized nanopowder was 100 ± 20 nm. Various composition of chitosan-CeO₂-CdO nanocomposites were developed using echo-friendly (mechanical mixing) technique. Pellets of 13.0 mm diameter and 1.0 ± 0.1 mm thickness were prepared using hydraulic press under the pressure of 375 MPa. Silver paste was used to deposit the electrodes; the length of each electrode was 12.0 mm and the gap between two electrodes was 2.0 ± 0.5 mm. The mechanism of sensing is based on impedimetric change in response to humidity variation. Fabricated sensors showed high sensitivities ranging from -930.0 kΩ/%RH to -2091.1 kΩ/%RH. Response and recovery times are up to 1 s, while the humidity sensing range is 5 to 95%RH. The fabricated sensors are very attractive to use in several devices for environmental monitoring and biomedical applications.