Phenanthroline-Based Reversible Fluorescent Probe for Ultrasensitive and Selective Detection of Ni²⁺ and...

In this study, bis-1,10-phenanthroline (Biphen) was synthesized via a hydrogen transfer-mediated coupling reaction in a single step. The resulting compound was demonstrated, for the first time, to function as a selective fluorescent probe for Ni²⁺ ions. The presence of Ni²⁺ at a 2:1 molar ratio of Biphen to Ni²⁺ results in complete fluorescence quenching, with a detection limit of 4.34 × 10^-9 M in aqueous medium. Fluorescence is restored upon the introduction of a suitable chelating agent, producing an "on-off-on" fluorescence switching response. Furthermore, fluorescence co-localization studies demonstrate that Biphen functions as a mitochondria-targeted fluorescent probe with excellent cell membrane permeability, enabling rapid, reversible imaging and ultratrace detection of Ni²⁺ in mitochondria of live cells. Overall, this work demonstrates highly selective ultratrace detection of Ni²⁺ in both aqueous and biological environments, providing a promising platform for mitochondrial imaging and potential diagnostic applications.