Ce3+ and Fe2+ co-enhanced ratiometric fluorescence probe utilizing copper nanoclusters and coumarin for sensitive assay of hydrogen peroxide and glucose

A novel ratiometric fluorescent probe was constructed for sensitive assay of hydrogen peroxide (H2O2) and glucose, which utilized the synergistically enhanced effects of Ce3+ and Fe2+ on copper nanoclusters (CuNCs) and coumarin. In the CuNCs-Ce3+/Fe2+-coumarin system, Ce3+ triggered the aggregation-induced emission phenomenon of CuNCs, and Fe2+ catalyzed the Fenton reaction to efficiently yield hydroxyl radical (•OH). In the presence of H2O2, the 625-nm red fluorescence of CuNCs was sharply quenched owing to the oxidation of CuNCs to Cu(II) by •OH, but the 460-nm blue fluorescence of 7-hydroxycoumarin from the oxidation of coumarin by •OH dramatically increased. Based on the reversible changes in two fluorescence signals, a satisfactorily ratiometric probe was constructed for H2O2 assay with a detection limit (LOD) of 0.6 μM accompanied by a visual color variation from red to blue. For glucose assay, this ratiometric probe gave a linear range of 3.2–160 μM and LOD of 0.96 μM owing to the oxidization of glucose to yield H2O2 in the presence of glucose oxidase and O2. Overall, the newly developed ratiometric probe shows a great prospect in real applications for visual assay of H2O2 and glucose by our naked eyes.