Double emission fluorescence probes based on unconventional fluorescent molecules and fluorescein isothiocyanate for ClO− and Cu2+ detection

• A novel strategy is provided to construct double emission fluorescence probes based on unconventional fluorescent molecules. • Fluorescein isothiocyanate, citric acid, and polyethyleneimine were treated hydrothermally to synthesize double emission unconjugated polymer dots ( f-PDs ). • Cu 2+ ions are combined with polyethyleneimine parts of f-PDs to form copper-amine complexes, the resulting internal filtration effect causes quench fluorescence. • ClO − can oxidize hydroxyl groups on the surface of f-PDs , resulting in fluorescence quenching. f-PDs have good water solubility, and high sensitivity. In recent years, unconventional fluorescent molecules without conjugated rings have attracted widespread interest due to their excellent fluorescence properties, simple preparation process, good water solubility and excellent biocompatibility. Dual emission fluorescent probes are usually more accurate and sensitive, for eliminating the influence of environmental factors. This work provides a novel strategy to construct double emission fluorescent probes based on unconventional fluorescent molecules and fluorescein isothiocyanate. The aqueous solution of resulting double emission polymer dots ( f-PDs ) shows two fluorescence emission peaks centered at 440 nm and 510 nm under excitation at 363 nm. According to change of these two peaks after adding ions, Cu 2+ and ClO − are judged quantitatively. Cu 2+ or ClO − are also quench fluorescence of f-PDs linearly, as Cu 2+ combines with polyethyleneimine parts of f-PDs to form complexes, while ClO − oxidize hydroxyl groups on the surface of f-PDs . The detection limits of Cu 2+ and ClO − , in an aqueous solution are 6.7 nM and 14.0 nM, respectively.