Fluorescence- and FRET-based mercury (II) sensor

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 the presence of sulphur 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 decrease with an increase in Hg2+ ion concentration. With proper optimisation, present system under investigations can be used to sense Hg2+ ions in aqueous solution with a 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.