Cesium-Doped Graphene Quantum Dots as Ratiometric Fluorescence Sensors for Blood Glucose Detection

Developing a highly sensitive fluorescence probe for biomolecule detection has a significant meaning in clinical diagnosis and research. Tuning the optical property of fluorescent nanomaterials by heteroatom doping is generally feasible to improve the application performance. In this work, a kind of cesium-doped graphene quantum dots (Cs-GQDs) are synthesized, characterized, and explored as a fluorophore in ultrasensitive determination of H2O2 and glucose. The prepared Cs-GQDs with a quantum yield of 39.8% eradiate intense blue fluorescence under UV irradiation. The emission of Cs-GQDs is almost excitation-independent. Doping Cs into the GQDs leads to a clear blue shift of the fluorescence emission peak, probably related to the increased band gap. In addition, Cs-GQDs show a pH-sensitive behavior under acidic conditions. In the presence of horseradish peroxidase, o-phenylenediamine could react with H2O2 to form a yellow fluorescent compound of 2,3-diaminophenazine (DAP). A ratiometric fluorescence probe toward H2O2 and glucose is established using the fluorescence resonance energy transfer mechanism between DAP and Cs-GQDs. This sensing strategy shows high sensitivity for H2O2 and glucose detection with detection limits of 25 and 23 nM, respectively, and excellent selectivity toward glucose out of various interferences. This method is extended to glucose detection in human serum samples. The present method provides a robust, sensitive platform for detecting various biological metabolites participating in the H2O2-generation reaction and shows promising potential for clinical diagnostics and research.