Cationic conjugated polyelectrolyte-based fluorometric detection of copper(II) ions in aqueous solution

A series of water-soluble cationic polyfluorene copolymer containing 2,2′-bipyridine moieties (PFP-P1–3) in the backbone were designed and synthesized as the fluorescent probes for Cu2+ ions. In the absence of the Cu2+ ion, the PFP-P2 exhibits strong fluorescence emission in aqueous solution. Upon adding the Cu2+ ion, the PFP-P2 coordinates to Cu2+ ions through weak N⋯Cu interactions, and its fluorescence is efficiently quenched by the Cu2+ ion with a Stern–Volmer constant (Ksv) of 1.44 × 107 M−1. The new method has high sensitivity with a detection limit of 20 nM. The minor interference from other heavy metal ions clearly shows that the PFP-P2 can be used as the Cu2+ ion probe with good selectivity.