Nguyen Khoa Hien

A new fluorescent chemosensor for Hg2+ in aqueous solution

We prepared an aminothiourea-derived Schiff base (DA) as a fluorescent chemosensor for Hg(2+) ions. Addition of 1 equiv of Hg(2+) ions to the aqueous solution of DA gave rise to an obvious fluorescence enhancement and the subsequent addition of more Hg(2+) induced gradual fluorescence quenching. Other competing ions, including Pb(2+), Cd(2+), Cr(3+), Zn(2+), Fe(2+), Co(3+), Ni(2+), Ca(2+), Mg(2+), K(+) and Na(+) , did not induce any distinct fluorescence changes, indicating that DA can selectively detect Hg(2+) ions in aqueous solution.

A new rhodamine-based fluorescent chemodosimeter for mercuric ions in water media

A new rhodamine-ethylenediamine-nitrothiourea conjugate (RT) was synthesized and its sensing property as a fluorescent chemodosimeter toward metal ions was explored in water media. Analytical results from absorption and fluorescence spectra revealed that the addition of Hg(2+) ions to the aqueous solution of the chemodosimeter RT caused a distinct fluorescence OFF-ON response with a remarkable visual color change from colorless to pink; however, no clear spectral and color changes were observed from other metal ions including: Zn(2+) , Cu(2+) , Cd(2+) , Pb(2+) , Ag(+) , Fe(2+) , Cr(3+) , Co(3+) , Ni(2+) , Ca(2+) , Mg(2+) , K(+) and Na(+) . The sensing results and the molecular structure suggested that a Hg(2+) -induced a desulfurization reaction and cyclic guanylation of the thiourea moiety followed by ring-opening of the rhodamine spirolactam in RT are responsible for a distinct fluorescence turn-on signal, indicating that RT is a remarkably sensitive and selective chemodosimeter for Hg(2+) ions in aqueous solution. Hg(2+) within a concentration range from 0.1 to 25 μM can be determined using RT as a chemodosimeter and a detection limit of 0.04 μM is achieved.

A highly sensitive fluorescent chemosensor for simultaneous determination of Ag(I), Hg(II), and Cu(II) ions

Simultaneous determination of the heavy metal ions at the µg/L level in an aqueous solution has always been attractive to scientists. Here, we present a simple, rapid and highly sensitive fluorescent chemosensor for simultaneous determination of mercury, copper, and silver ions in an aqueous solution in the presence of various competitive metal ions, including Na + , K + , Ca 2+ , Ba 2+ , Mg 2+ , Pb 2+ , Cd 2+ , Co 2+ , Zn 2+ , Fe 2+ , Ni 2+ , Al 3+ , and Cr 3+ ions. The detection limits of the sensor for Hg 2+ , Cu 2+ , and Ag + ions are 2.8, 0.8, and 1.0µg/L, respectively. This sensor is potentially suitable for detecting and monitoring these metal ions in drinking water samples according to the regulations of the World Health Organization.

A fluorescent sensor based on dansyl-diethylenetriamine-thiourea conjugate: a through theoretical investigation

A new dansyl-diethylenetriamine-thiourea conjugate (DT) for detection of Hg 2+ ions in aqueous solution has been theoretically designed and compared to our previously published results. The synthetic path, the optimized geometric structure and the characteristics of the DT were found by the theoretical calculations at the B3LYP/LanL2DZ level. Accordingly, the DT can react with Hg 2+ ion to form a product with quenched fluorescence. It is remarkable that the experimental results are in an excellent agreement with the theoretically evaluated data. Keywords. Fluorescence, chemodosimeter, dansyl, diethylenetriamine, thiourea, Mercury, TD-DFT, PET.