A versatile fluorescent dye based on naphthalimide: highly selective detection of Hg2+ in aqueous solution and living cells and its aggregation-induced emission behaviour

A simple and versatile fluorescent dye NPS based on 1,8-naphthalimide was successfully designed and prepared. It was found that NPS exhibited excellent selectivity for Hg2+ over many other metal ions including Zn2+, Mn2+, Ba2+, Ni2+, Cu2+, Co2+, Pb2+, Mg2+, Cd2+, Fe2+, Al3+, Ag+, Na+, and Li+. In particular, NPS displayed a significant fluorescence turn-on to Hg2+ in aqueous solution and living cells, which could be potentially used for quantification of Hg2+. Moreover, two model compounds were rationally designed and synthesized, from which further insight into the sensing mechanism and binding mode of NPS with Hg2+ was obtained. Surprisingly, NPS exhibited interesting twisted intramolecular charge transfer (TICT) and aggregation-induced emission (AIE) behaviours in aqueous solution.