Fluorescent Polyamide-Based Rhodamine Hydrazide Moieties with Oxethyl as Spacer for Detection of Cr3+, Fe3+, and Hg2+ Ions in Water

An acrylic monomer bearing xanthene group, N-oxethyl acrylate-N'-rhodamine B hydrazide (ARBHE) was synthesized from N-hydroxyl ethyl-N'-rhodamine hydrazide (RBHE) and acryloyl chloride (Ac) in the presence of triethylamine in dry dichloromethane (CH2Cl2) at room temperature. The synthesized ARBHE was identified by FTIR, H-1 NMR spectra and elementary analysis. Copolymer poly(AM-ARBHE) of ARBHE and AM was synthesized with thermal initiator by free radical precipitation polymerization and it was characterized by the method of FTIR and H-1 NMR. Its molecular weights (M-eta) was 7.03 x 10(3) g mol(-1) and the content of rhodamine units in the polymer chains was 1.44 % in mole fraction. The ability of the poly(AM-ARBHE) to detect different metal cations (Ag+, Ba2+, Cd2+ Co2+, Cr3+, Cu2+, Co2+ K+, La3+, Mg2+, Na+, Ni2+, Pb2+, Fe2+, Fe3+, Hg2+ and Zn2+) in water was investigated. Upon addition of Cr3+, Fe3+ or Hg2+ ions to the aqueous solution, visual color change and fluorescence enhancement were observed. Moreover, other metal ions did not induce obvious changes to the fluorescence spectra except to Fe2+. The detection limit of poly(AM-ARBHE) was less than 1 x 10(-11) M. The results suggest that this copolymer may offer potential as a polymeric sensor for Cr3+, Fe3+ and Hg2+ ions in water.