A new red fluorescent probe for Hg2+ based on naphthalene diimide and its application in living cells, reversibility on strip papers

A new fluorescent probe (NDI-5) towards Hg2+ ions has been designed and synthesized based on naphthalene diimide (NDI), which showed extremely weak fluorescence emission in solution owing to the twisted intermolecular charge transfer (TICT) between the NDI core and the receptor. However, upon the addition of Hg2+ ions, a “turn-on” fluorescence response with red emission was obvious with 32-fold enhancement of the quantum yield, and the detection limit was as low as 1.3 μM. Furthermore, NDI-5 can be applied to MCF-7 cells to realize the detection of Hg2+ ions in the living systems, and the reversibility with the coordination of KI can be conducted in solution and test stripes for several times.