Comprehensive Study of Poly(2,3,5,6-tetrafluoroaniline): From Electrosynthesis to Heterojunctions and Ammonia Sensing

In this work, we report for the first time on a comprehensive study of poly(2,3,5,6-tetrafluoroaniline) (PTFANI). Contrary to the nonfluorinated polyaniline (PANI) or its analogues bearing one fluorine atom, PTFANI is a poorly conductive material. We present a comprehensive study of the electrosynthesized PTFANI from its monomer in an acidic aqueous medium. PTFANI was fully characterized by a potential–pH diagram, spectroelectrochemistry, and electrochemical quartz crystal microbalance (EQCM) measurements, as well as by a morphological study. Combined with the X-ray photoelectron spectroscopy (XPS) analysis, it allowed us to understand the redox properties of this polymer compared to those of the unsubstituted PANI. At pH < 1.85, no proton transfer occurred during the electrochemical process, but the insertion of anions at the site of the protonated imines was demonstrated through the EQCM and XPS experiments. PTFANI showed a lower ratio of 1 ClO4– per 3 2,3,5,6-tetrafluoroaniline units compared to that o...