Highly sensitive ammonia sensors obtained by synergetic effects of polypyrrole and ionic liquid

Polypyrrole (PPy) is a well-known conducting polymer with significant sensing capabilities for ammonia detection. In parallel, Ionic Liquids (ILs) have been developed as an alternative to water to absorb ammonia. Convinced that a combination of PPy and IL will allow to increase the sensors’ sensibility, we developed in this study microconductometric ammonia sensors composed of PPy and ILs-functionalized PPy. These sensors were fabricated by electropolymerization on interdigitated electrodes. The resulting films incorporated various counterions, namely bis(trifluoromethylsulfonyl)imide (TFSI^-), hexafluorophosphate (PF₆^-) and tetrafluoroborate (BF₄^-). Two series of sensors were prepared containing either pure PPy or copolymers functionalized with ILs. The sensing performances of these sensors towards ammonia were tested and compared. It is mesmerizing to realize that all the sensors containing ionic liquids demonstrated superior responses to NH₃, experimentally detecting concentrations as low as 1 ppm under ambient conditions. Remarkably, the PPyIm-TFSI-based sensor exhibited the highest sensitivity and relative response of −4.72 %.ppm⁻¹ and −65 %, respectively, with an impressive limit of detection of 63 ppb. Meanwhile, the PPyIm-BF₄-based sensor displayed the fastest adsorption/desorption kinetics (t₉₀) of 19 s/26 s, respectively. These characteristics makes these sensors some of the most effective organic chemoresistive sensors reported so far for real-environmental applications.