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-P-2 exhibits strong fluorescence emission in aqueous solution. Upon adding the Cu2+ ion, the PFP-P-2 Coordinates to Cu2+ ions throUgh weak N center dot center dot center dot Cu interactions, and its fluorescence is efficiently quenched by the Cu2+ ion with a Stern-Volmer constant (K-SV) of 1.44 x 10(7) 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-P-2 can be used as the Cu2+ ion probe with good selectivity. (c) 2008 Elsevier Ltd. All rights reserved.