Detection of Lead(II) in Living Cells by Inducing the Transformation of a Supramolecular System into Quantum Dots

Due to the high toxicity of Pb2+, efficient in situ detection of Pb2+ is very important. Herein, a new approach for in situ probing of Pb2+ by inducing supramolecular systems to form fluorescent quantum dots (QDs) is demonstrated. At the beginning of this work, a new tetra-pillar[5]arene derivative was designed as host H. The H and an amphiphilic guest G could assemble into supramolecular systems in aqueous solution and form nanoparticles without fluorescence emission. Interestingly, S2- could crosslink the nanoparticles, changing them into fluorescent nanorods. Notably, the Pb2+ could induce these nanorods to in situ transform into PbS QDs; meanwhile, the system showed distinct fluorescent changes, and the fluorescence quantum yield of the system showed a dramatic increase. This in situ PbS QD formation process could be applied in efficient Pb2+ sensing in water and living cells. This research also provides a simple and feasible way to detect heavy metal ions by in situ construction of fluorescent nanomaterials and QDs through a supramolecular approach.