Pyrene excimer-based fluorescent sensor for detection and removal of Fe3+ and Pb2+ from aqueous solutions.

Pyrene excimer usually serves as a chromogenic unit for developing ratiometric fluorescent sensors. But this study used excimer as a large hydrophobic group to regulate the molecular hydrophobicity, and obtained a new fluorescent sensor, N, N-bi[4(1-pyrene)-butyroyl]ornithine (1), for detection and removal of Fe3+ and Pb2+ from aqueous solutions. The coordination of 1 and Fe3+ in the aqueous solution or even pure water forms removable flocculent precipitates, accompanied by obvious fluorescent quenching of emission spectra. In aqueous solutions containing 40% (v/v) acetonitrile, the special responses exhibit a high selectivity and sensitivity to Fe3+ over other common metal ions. However, in aqueous solutions containing 40% (v/v) dimethylsulfoxide, the probe exhibits the analogous fluorescent quenching responses and the removable flocculent precipitates in the presence Fe3+ and Pb2+. These results indicate that the extremely hydrophobic 1-Fe3+/Pb2+ complexes are not only a supplement to the fluorescent sensing of Fe3+ and Pb2+, but also a requirement to the removal of Fe3+ and Pb2+ from aqueous solutions.

2-(1-Pyrenyl) benzimidazole as a ratiometric and "turn-on" fluorescent probe for iron(III) ions in aqueous solution.

A highly selective and sensitive ratiometric and "turn-on" fluorescent probe for Fe(3+), 2-(1-pyrenyl) benzimidazole (L), was synthesized by a one-step process. In emission spectra, the relative intensity ratio of excimer to monomer fluorescence (IE450/IM387) of L increased 510-fold upon the addition of 30 equiv. of Fe(3+) with a detection limit of 0.2 µM (11.2 ppb) in aqueous solution. Meanwhile, the fluorescence excitation spectra of L showed a fluorescent "turn-on" probe for Fe(3+) with 30-fold enhancement in excitation band intensity of excimer.

Selective and sensitive fluorescence-shift probes based on two dansyl groups for mercury(ii) ion detection.

Two probes ( and ) bearing two dansyl fluorophores were synthesized and applied to the detection of mercury(ii) ions in aqueous solution. These probes exhibited a selective response to Hg(2+) in a buffered solution, with high sensitivity and a unique fluorescence response signal which displayed a blue-shift effect in the fluorescence emission peak. The Hg(2+) recognition mechanisms of the probes were determined by NMR spectroscopy, ESI-MS and UV-vis spectroscopy. The results showed that probe and mercury(ii) ions formed an unusual 2:2 stoichiometric ratio complex, while probe and Hg(2+) formed a multidentate complex with a stoichiometric ratio of 2:1.