Thymine functionalized graphene oxide for fluorescence "turn-off-on" sensing of Hg²⁺ and I^- in aqueous medium

Selective detection of either mercury (Hg²⁺) or iodide (I^-) ion using fluorescence turn-on or turn-off processes is an important area of research. In spite of intensive research, simultaneous detection of both mercury and iodide using fluorescence turn-off-on processes, high sensitivity and theoretical support concerning the mechanisms are still lacking. In the present work, graphene oxide is functionalized by thymine to realize simultaneous detection of both Hg²⁺ and I^- selectively using fluorescence turn-off-on mechanism. Ultra high sensitivity to the extent of ppb level exploiting large surface area of graphene is achieved. DFT calculations also assist to realize the detailed mechanisms involving this PL quenching and also its regain during sensing of these ions in aqueous solution.