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 1H 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 1H NMR. The viscosity average molecular weight Mη– of poly(AM-AA) and poly(AM-AA-AR6GH)s were 1.76 × 106, 8.58 × 104 and 7.68 × 104 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.