Hg2+ detection by aniline-based conjugated copolymers with high selectivity

Conjugated polymers (P1, P1L and P2–P5) constructed by alkynyl-substituted aniline and substituted arene analogs could be synthesized through Pd-catalyzed Sonogashira coupling. The responsive optical properties of poly(2-ethynyl aniline) (P1 and P1L for different molecular weights, P1L with longer chains on average) toward various metal ions (including Ni2+, Ag+, Cu2+, Zn2+, Fe3+, Fe2+, Mn2+, Na+, Ca2+, Pb2+, K+, Cr3+, Al3+, Cd2+, Pt2+, Au3+ and Tl3+) were investigated. Hg2+ exhibited the most pronounced fluorescence response of both P1 and P1L without interference from those coexistent ions due to aniline in the polymer backbone as the metal binding ligand, while other metal ions does not cause obvious change of fluorescence. Compared with P1, P1L exhibits better sensitivity toward Hg2+. Introducing pyridyl, thienyl or phenyl groups into the polymer backbone would weaken the quenching responses to Hg2+ compared with P1. The results indicated P1 and P1L could be used as a selective fluorescence sensor toward Hg2+.