Carbon quantum dots based ratiometric fluorescence probe for sensitive and selective detection of Cu2+ and glutathione

A novel method was established for the ratiometric fluorescence detection of Cu2+ and glutathione (GSH) by carbon quantum dots (CQDs), and it was fabricated through one-pot facile hydrothermal treatment using o-phenylenediamine (OPD) and citric acid as precursors. Based on the selective oxidation reaction of OPD with Cu2+, the detection strategy of Cu2+ was proposed using ratiometric fluorescence probe. The oxidation production (2,3-diaminophenazine) of OPD, obtained through the oxidation reaction of OPD and Cu2+, not only emerged a new emission peak at 562 nm, but also quenched the fluorescence of CQDs with maximum emission at 446 nm. The mechanism was Förster resonance energy transfer (FRET) between CQDs and 2,3-diaminophenazine (oxOPD). Furthermore, the oxidation reaction between Cu2+ and OPD could be inhibited when added GSH into the solution, which could prevent the fluorescence of CQDs being quenched. The sensing system showed high sensitivity toward Cu2+ and GSH in a range of 0.25–10.0 μmol L−1 and 1.0–80.0 μmol L−1 with a detection limit 0.076 μmol L−1 and 0.30 μmol L−1, respectively. Besides, the proposed method could apply to efficient quantification of Cu2+ and GSH in practical samples.