A flexible polypyrrole/silk-fiber ammonia sensor assisted by silica nanosphere template

Flexible polypyrrole (PPy)@silk-fiber and PPy@sponge sensors were fabricated using the silica nanosphere (SiO₂ NS) template via a facile in situ chemical oxidation polymerization method. Exposed to 100 ppm NH₃ gas at room temperature in 68 ± 5 % relative humidity (RH), the response of the PPy/NS@silk-fiber sensor (73.25 %) was five-fold higher than that of the PPy/NS@sponge sensor (14.51 %). Meanwhile, the recovery time (69 s) of the PPy/NS@silk-fiber sensor was reduced to two-thirds of that (98 s) of the PPy/NS@sponge sensor for 100 ppm NH₃. Additionally, the PPy/NS@silk-fiber sensor exhibited excellent reproducibility, flexibility, selectivity, and long-term stability to NH₃ at room temperature. The improved gas-sensing properties can be attributed to the high surface area of the flexible PPy/NS@silk-fiber with relative rough hill-like shapes. This investigation indicated that the PPy/NS@silk-fiber is promising sensing material for developing flexible and wearable NH₃ sensors.