Humidity sensing properties of poly(o-anisidine)/WO3 composites

The present investigation reports the humidity sensing properties of poly(o-anisidine)/WO3 (POA/WO3) composites. The POA/WO3 composites with different WO3 weight percents were prepared by a simple mechanical mixing method. These composites were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Humidity sensing properties of the composites were investigated, including the resistance versus relative humidity, humidity hysteresis, response time, repeatability and long-term stability. The results indicate that the humidity sensing properties of the POA/WO3 composites are better than those of pure POA. The composites respond more rapidly to humidification and desiccation steps than POA. The composite with 30 wt% of WO3 shows the maximum percentage response factor (Sf) ∼353 at 85% RH, narrow hysteresis (∼6%) and an excellent repeatability of the response. Furthermore, it was found to be stable for more than 30 days.