Synthesis of a water-soluble copolyacrylamide bearing rhodamine B derivative and its selective detection of Fe3+ in aqueous solution

A polymerizable rhodamine-based monomer 2-(3-(2-(3′,6′-bis(diethylamino)-3-oxospiro[isoindoline-1,9′-xanthen]-2-yl)ethyl)ureido)ethyl acrylate (RhBUEA) is first designed and synthesized, and then used in the preparation of a new water-soluble P(AM-co-RhBUEA) through precipitation polymerization of it with acrylamide (AM). Influence of the RhBUEA content on the polymerization process is investigated, and the chemical structure and composition of the copolymers are confirmed by FTIR and UV–vis spectral analysis. According to the off-on switch between spirolactam and ring-opened form of rhodamine derivative, P(AM-co-RhBUEA) prepared with 15 wt.% RhBUEA exhibits a highly sensitive and selective recognition towards Fe3+ in aqueous solution with 0.073 μM of detection limit, accompanied with a remarkable spectral and color change. Furthermore, the spectral response is reversible by the alternating addition of Fe3+ and EDTA to the copolymer, and the test strips prepared by P(AM-co-RhBUEA) can detect Fe3+ colorimetrically and portably, which makes the water-soluble polymer a promising Fe3+ sensor in the field of on-site detection.