Enhanced Sensitivity and Stability of Room-Temperature NH3 Sensors Using Core–Shell CeO2 Nanoparticles@Cross-linked PANI with p–n Heterojunctions

We report a room-temperature NH3 gas sensor with high response and great long-term stability, including CeO2 NPs conformally coated by cross-linked PANI hydrogel. Such core-shell nanocomposites were prepared by in situ polymerization with different weight ratios of CeO2 NPs and aniline. At room temperature, the nanohybrids showed enhanced response (6.5 to 50 ppm of NH3), which could be attributed to p-n junctions formed by the intimate contact between these two materials. Moreover, the stability was discussed in terms of phytic acid working as a gelator, which helped the PANI sheath accommodate itself and enhance the mechanical strength and chemical stability of the sensors by avoiding "swelling effect" in high relative humidity. The sensors maintained its sensing characteristic (response of ca. 6.5 to 50 ppm of NH3) in 15 days. Herein, the obtained results could help to accelerate the development of ammonia gas sensor.