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Novel sea cucumber-shaped polyaniline/ferric oxide (PANI/Fe 2 O 3 ) nanocomposites were synthesized using a simple and efficient one step hydrothermal process, and the nanocomposites were further assembled onto a polyethylene terephthalate (PET) flexible substrate. Through the monitoring of the resistance of the PANI/Fe 2 O 3 nanocomposites thick films and PANI/Fe 2 O 3 -PET flexible sensors, the responses of the sensors to various 100 ppm gases including methanol, triethylamine, aniline and another five gases were obtained. It was found that two kinds of sensors exhibit a high selectivity towards NH 3 . The PANI/Fe 2 O 3 nanocomposites-based sensor has a good response and a low detection limit (0.3 ppm) at room temperature (20±5 °C). It also shows a good linearity relationship in a certain concentration of NH 3 . After assembling into the PANI/Fe 2 O 3 -PET flexible film sensor, the response of the sensor is significantly increased to 6.12 for 100 ppm NH 3 , the detection limit is as low as 0.5 ppm, and the sensor shows good stability and linearity, which is more conducive to the application of such a material in wearable gas sensors.

PANI/TiO2 nanocomposites spheres were synthesized using a simple and efficient one-step hydrothermal process. The morphology and structure of PANI/TiO2 nanocomposites spheres were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The PANI/TiO2 nanocomposite sphere-based sensor exhibits good selectivity, sensitivity (5.4 to 100 ppm), repeatability, long-term stability and low detection limit (0.5 ppm) to ammonia at room temperature (20 ± 5°C). It also shows a good linearity relationship in the range of 0.5–5 and 5–100 ppm. The excellent NH3 sensing performance is mainly due to the formation of the p-n heterostructure in the nanocomposites.

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