Graphene quantum dots combined with the oxidase-mimicking activity of Ce 4+for ratiometric fluorescent detection of Ce 4+and alendronate sodium

A simple ratiometric fluorescent sensing system for Ce4+ and alendronate sodium (ALDS) detection is developed with graphene quantum dots (GQDs) combined with the oxidase-mimicking activity of Ce4+. As oxidase-mimicking, Ce4+ can catalyze the oxidization of o-phenylenediamine (OPD) directly without the requirement of H2O2. The oxidation product (oxOPD) not only exhibits a strong emission at 562 nm but also quenches the fluorescence of GQDs at 444 nm significantly through inner filter effect (IFE). Due to its strong oxidative ability, Ce4+ can also oxidize ALDS. Thus, ALDS can inhibit the oxidization of OPD by Ce4+. The fluorescence at 444 nm can be protected from quenching while that at 562 nm decreases. Thus, a ratiometric fluorescent strategy for quantitative analysis of Ce4+ and ALDS has been developed. The ratiometric sensing platform exhibits a high sensitivity with the detection limits of 1.0 μM and 33 nM for Ce4+ and ALDS, respectively. This strategy can detect Ce4+ and ALDS in practical samples with satisfactory recoveries. © 2020 Elsevier B.V.