Metal ions recognition by pyrene labeled poly(acrylic acid)

Abstract

In the present work, we assessed the sensing of multiple transition metal ions (Men+) using pyrene labeled poly(acrylic acid) (PAA25Py3). The UV–vis, steady-state (excitation and emission) and time-resolved fluorescence as well as FTIR measurements were performed. The comparative effect of Ag+, Cu2+ and Fe3+ on the optical properties (the monomer and excimer maximum intensity, the polarity/conformational index as well as the fluorescence quantum yield and lifetime) of the pyrene (Py) label was evaluated. The influence of the other metal ions (i.e., Li+, K+, Na+, Ba2+, Ca2+, Zn2+, Ni2+ and Al3+) on the Py photophysics was investigated. The fluorescence quenching of both Py monomer and excimer by appropriate amounts of Ag+, Cu2+ and Fe3+ was revealed. The quenching curves of Py were analyzed with the Stern-Volmer equation. The detection limit, the quenching and the binding constants were calculated. The fluorescent polymer showed higher sensitivity, selectivity and binding ability for Fe3+ than Cu2+ and Ag+. It was revealed the occurrence of the electron transfer from the amide group of PAA25Py3 to Py label, the formation of coordination complexes between several Cu2+/Fe3+ ions and carboxylic units of PAA25Py3 as well as the photoinduced electron transfer from excited Py to complexed Men+. The results proved that the pyrene labeled poly(acrylic acid) can be used as a potential fluorescent sensor to detect both Fe3+ and Cu2+ ions.