Comparison of two rhodamine-based polystyrene solid-phase fluorescent sensors for mercury(II) determination

Two novel rhodamine-based polystyrene solid-phase fluorescent sensorsPS-AC-IandPS-AC-IIwith different coordination atoms (O or S) are synthesized and shown to be able to detect Hg(II) ions. They are characterized by Fourier-transform infrared spectroscopy and by scanning electron microscopy analysis. Their fluorescent properties, including response time, pH effects, fluorescence titrations, metal ion competition and recycling, are investigated and compared. SensorPS-AC-IIdisplayed higher selectivity and sensitivity to Hg(II), with a lower detection limit of 0.032 mu M, which was 15 times better thanPS-AC-I. A detection mechanism involving the Hg(II) chelation-induced ring-opening of the rhodamine spirolactam is proposed with the aid of theoretical calculations.