A sensitive pH fluorescent probe based on triethylenetetramine bearing double dansyl groups in aqueous solutions and its application in cells.

pH fluorescent probes possess many advantages, including intracellular detection, rapid response time and nondestructive testing. In this paper, a highly selective and sensitive fluorescent pH probe based on triethylenetetramine bearing double dansyl groups (1) was synthesized. This probe offers fluorescent measurement of pH value in the range of 5.81-7.21 in aqueous solution, with an 8.64-fold enhancement of fluorescent emission intensity over the unmodified probe. Probe 1 shows a fluorescent color change from a pale yellow to bright green when the pH is increased from 5.81 to 7.21. In addition, probe 1 shows good potential as a fluorescent visualizing sensor for pH values in living GS cells of epinepheluscoioides. The mechanism of the fluorescent response of probe 1 to solution pHs was further clarified by NMR, fluorescent spectra, and UV-vis absorption spectra. The results indicate that the fluorescent emission will shift with an increase in solution pHs, due to increasing deprotonation of the nitrogen atom on the sulfonamides. Deprotonation of the sulfonamide group will inhibits the intramolecular charge transfer process between the imino group and the naphthalene ring, resulting in the recognition phenomenon of blue shift and enhancement of fluorescent emission intensity.

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.