A Rapid Response Humidity Sensor Based on Poly(2,5-dimethoxyaniline)-tin Oxide Nanocomposite

Poly(2,5-dimethoxyaniline)-tin oxide (PDMA-SnO2) nanocomposites were synthesized successfully for the first time through an in situ chemical polymerization of 2,5-dimethoxyaniline in the presence of SnO2 nanoparticles of 25-40 nm in diameters. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were used to characterize the PDMA-SnO2 nanocomposites. The characterization results confirmed the polymerization of 2,5-dimethoxyaniline and the strong interaction between PDMA and SnO2 nanoparticles. Humidity sensing characteristics such as humidity response-relative humidity (RH) property, humidity hysteresis, response and recovery times, reproducibility and stability of PDMA-SnO2 have been investigated. The nanocomposite with 50 wt% of SnO2 exhibited better humidity sensing properties than pure PDMA, such as rapid response (similar to 3 s), fast recovery (similar to 43 s), hysteresis within 5% and excellent reproducibility. Plausible humidity sensing mechanism of PDMA-SnO2 nanocomposite is also discussed.