A resistive type humidity sensor based on crystalline tin oxide nanoparticles encapsulated in polyaniline matrix

We have synthesized a nanocomposite consisting of crystalline tin oxide (SnO₂) nanoparticles and polyaniline (PANI) by in-situ polymerization and composite formation (IPCF). The structure and morphology was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The nanocomposite is shown to represent a viable material for electrical resistivity based sensing of humidity in the 5 to 90 % relative humidity (RH) range. The electrical resistance of the composite linearly decreases from 127.5 to 11.5 kΩ with humidity from 5 to 95 %. The sensitivity is 0.22 % RH‾¹, the response time is 26 s, and the recovery time is 30 s. The fabrication of SnO₂/PANI composite combines the high sensitivity of SnO₂ towards moisture with good electrical conductivity of PANI, which influences the electronic properties of the material and enables the design of more efficient humidity sensors. The water vapor layering growth kinetics on the composite was investigated by isothermal thermogravimetric analysis and an interaction with limited diffusion aggregate type kinetics has been proposed.