Fluorogenic detection of Hg2+, Cd2+, Fe2+, Pb2+ cations in aqueous media by means of an acrylamide-acrylic acid copolymer chemosensor with pendant rhodamine-based dyes

A monomer 1-acrolyl-2-rhodamine 6G hydrazide (AR6GH) was synthesized by the heterogeneous reaction of acryloyl chloride with rhodamine 6G hydrazide (R6GH) and characterized by H-1 NMR, FTIR and elememtal analyses. Then it was micellar copolymerized with acrylamide (AM), acrylic acid (AA) to obtain a water-soluble fluorescent copolymers (poly(AM-AA-AR6GH)) which were characterized by the method of FTIR and H-1 NMR. The viscosity average molecular weight (M) over bar (eta) of poly(AM-AA) and poly(AM-AA-AR6GH)s were 1.76x10(6), 8.58x10(4) and 7.68x10(4) g/mol, respectively. The fluorescent characteristic of the aqueous solutions of copolymers was investigated both in varied pH and in the presence of metal cations. The poly(AM-AA-AR6GH) was found to be a selective chemosensor for Hg2+, Cd2+, Fe2+, Pb2+ ions. Obvious fluorescence enhancement was due to the photophysical response of the copolymer to the presence of Hg2+, Cd2+, Fe2+, or Pb2+ ions. In addition, the ability of the copolymer to detect different metal cations (Ag+, Ba2+, Co2+, Cd2+, Cr3+, Cu2+, Fe2+, Fe3+, Hg2+, K+, Mg2+, Mn2+, Na+, Ni2+, Pb2+, Zn2+) in aqueous solution was studied. The results suggest that copolymer may offer potential application for sensors of Hg2+, Cd2+, Fe2+, or Pb2+ ions in aqueous solution.