An aggregate characteristic of relay fluorescence probe for Cu2+/HPO42- with improved low detection limit based on aggregation-switching mechanism

A new pyrrole-modified phenanthrene[9,10-d]imidazole derivative (PIPy) with aggregate characteristic in aqueous medium has been developed. In DMF/H2O solution (v/v, 1/1, HEPES, 10 mu M), PIPy exhibits overt aggregated performances with the flat absorption, strong fluorescence emission, and perceptibly cumulate morphology. On the basis of aggregation, PIPy displays the selective and sensitive fluorescence response to Cu2+ as the form of PIPy-Cu2+ complex which breaks down the original aggregated state of PIPy and leads to the fluorescence damping. Subsequently, in situ PIPy-Cu2+ complex as a fluorescence platform can achieve the consequent increment in fluorescence emission through the highly sensitive detection of HPO42-; at this moment, Cu2+ is employed by HPO42- and then PIPy is released again with the re-formed aggregation in water solution, resulting in the fluorescence renewing. The relay fluorescence recognition for Cu2+/HPO42- is perfectly realized with "on-off-on" fluorescence signal based on the aggregation-switching mechanism. Especially, the excellent limit of detection for Cu2+ and HPO42- is as low as 395.77 and 120.38 nM, respectively. In addition, this fluorescence switching for successive Cu2+ and HPO42- is successfully used to detect the real samples (water and feed) with good recoveries and small relative standard deviations. Finally, PIPy is applied for the intracellular imaging in HeLa cells manifesting the negligible toxicity and excellent biocompatibility.