A polymeric film probe with a turn-on fluorescence response to hydrogen sulfate ions in aqueous media

A new kind of hydrophilic copolymer poly(HEMA-co-VNP) was designed and synthesized by the radical copolymerization of 2-hydroxyethylmethacrylate (HEMA) and 2-{[2-(4-vinylbenzyloxy)naphthalen-1-yl]methyleneamino}-(S)-2-phenylethanol (VNP). The desired copolymer showed a highly selective red-shifted emission and a unique chiroptical response upon HSO₄ ^- binding in organic solution. UV-vis and ¹H NMR spectroscopic studies revealed that the hydrogen bonding between the imine moiety in the VNP repeating units and HSO₄ ^- is crucial for the high selectivity of the receptor to this anion. As expected, the incorporation of HEMA into the polymer matrix endowed the copolymer excellent hydrophilicity, flexibility and good film-forming properties. Thus, high-quality film sensors could be easily fabricated on quartz plates through spin-casting techniques. The resultant polymeric films can recognize HSO₄ ^- ions among a series of common anions in aqueous solution with high selectivity and sensitivity. The promising new film probe for HSO₄ ^- has distinct characteristics such as a rapid response, enough stability in an aqueous media and practicality.