Differentiated regulation of the interactions between ions, water and polymer is an effective way to get high-quality thermopower.

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.

Hierarchical Cr-doped WO3 microspheres have been successfully synthesized for efficient sensing of H2S gas at low temperatures. The hierarchical structures provide an effective gas diffusion path via well-aligned micro-, meso-, and macroporous architectures, resulting in significant enhancement in sensing response to H2S. The temperature and gas concentration dependence on the sensing properties elucidate that Cr dopants remarkably improve the response and lower the sensor' operating temperature down to 80 °C. Under 0.1 vol % H2S, the response of Cr-doped WO3 sensor is 6 times larger than pristine WO3 sensor at 80 °C. We suggest the increasing number of oxygen vacancies created by Cr dopants to be the underlying reason for enhancement of charge carrier density and accelerated reactions with H2S.

Gas sensors based on a noble metal-semiconductor are widely used, and they show a positive temperature response to hydrogen below 400 C. In this study, a catalytically activated hydrogen sensor is obtained based on Pd decorated WO 3 nanoplates constructed by a solvothermal method. An insight into the role of Pd catalyst in the outstanding performance is provided by comparing the sensing properties of this sensor with those of a traditional one made from the same pristine WO 3 . The pure WO 3 sensor exhibits poor selectivity and low sensitivity to hydrogen. In contrast, the observed response of the as-produced sensor is up to 843 at a low operating temperature of 80 C; the response value is even greater than that of WO 3 sensors at high temperatures (250-400 C). In addition, the Pd-loaded WO 3 sensors show excellent selectivity towards H 2 in comparison to other common gases (CH 4 , C 3 H 6 O, C 2 H 6 , C 3 H 8 O and NH 3 ). The significantly improved performance is thoroughly explained in terms of the adsorptiondesorption mechanism and chemical kinetics theories. Furthermore, an interfacial model demonstrated in this report indicates that the interfacial barrier between WO 3 nanoparticles can be a novel effect for excellent gas sensing performance.