Simple and sensitive detection method for Cobalt(II) in water using CePO4:Tb3+ nanocrystals as fluorescent probes

A simple and sensitive method for detecting cobalt by synchronous fluorescence spectrometry technique with a novel fluorescence probe CePO4:Tb3+ has been developed. CePO4:Tb3+ nanocrystals were synthesized in aqueous solutions and characterized by transmission electron microscopy, electron diffraction pattern spectroscopy and spectrofluorometry. When Δλ = 210 nm, the selected synchronous fluorescence is produced at 284 nm. CePO4:Tb3+ nanocrystals were negatively charged under weakly basic conditions (pH = 8.2), which can interact with Co2+ via electrostatic interaction. Moreover, there is the spectrum overlap between the emission wavelength of CePO4:Tb3+ NCs and the absorbance of Co2+. So the energy transfer would occur, leading to the quenching phenomenon. The quenching equation of the system was agreed with the Stern–Volmer equation. The linear range and detection limit of Co2+ were 5–1.8 μM and 3.5 nM, respectively. The method is successfully applied to the quantification of Co2+ in water samples.

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► A new method was developed for determination of Co2+.
► CePO4:Tb3+ NCs were synthesized and used as fluorescent probes.
► The probable quenching mechanism is an energy transfer process which from CePO4:Tb3+ nanocrystals to Co2+.