  A mercury (II) sensor has been proposed based on Fluorescence Resonance
Energy Transfer (FRET) between N,N'-dioctadecyl thiacyanine perchlorate (NK)
and Octadecyl rhodamine B chloride (RhB). Out of these two molecules NK is
sensitive to Hg2+ ions due to presence of sulfur atom in it. Accordingly,
presence of Hg2+ ions affects the NK fluorescence as well as FRET from NK to
RhB. Our results showed that NK fluorescence intensity and FRET efficiency
linearly decreases with increase in Hg2+ ion concentration. With proper
optimization present system under investigations can be used to sense Hg2+ ions
in aqueous solution with detection limit of 9.13 ppb. Advantage of this present
system is that it is very simple compared to the other FRET based system and
also it works under aqueous environment. This method has also been tested using
real lake water and satisfactory results were obtained.
