Enhanced ammonia-sensing properties of PANI-TiO2-Au ternary self-assembly nanocomposite thin film at room temperature

Polyaniline-titanium dioxide-gold (PANI-TiO2-Au) ternary nanocomposite thin film was prepared on gold interdigital electrodes by in-situ self-assembly method at room temperature (∼25 °C) for ammonia (NH3) detection. The morphological, structural and chemical features of the film were analyzed by different characterization methods (FESEM, TEM, XRD, UV-vis and FTIR spectra), and the real-time response properties of sensor were evaluated when exposed to 10-50 ppm NH3 at room temperature. The results showed that PANI-TiO2-Au ternary thin film sensor possessed superior response characteristics compared with the PANI-TiO2 binary one, including the higher response values (48.6%-123%), shorter response times (52 s-122 s) and better reversibility, which might be ascribed to the synergistic enhancement effect of nano-junctions (including the p-n junction and Schottly junction) and the catalysis of Au nanorods. Furthermore, the PANI-TiO2-Au ternary thin film sensor exhibited excellent repeatability, remarkable selectivity, acceptable stability (∼68%) and low detectable concentration (1 ppm) to NH3. Besides, the effect of the relative humidity on the sensing properties was also discussed. This work exhibited that the prepared ternary nanocomposite thin film would be promising for the development of room-temperature operation NH3 sensor.