Ratiometric fluorescent nanosensor for dosage-sensitive visual discrimination of glucose based on electron transfer mechanism

Owing to the great role of glucose in biological systems and food industry, it is significant to maintain the dynamic balance of organisms. Various methods widely reported are focused on the glucose detection with high sensitivity and low detection limit. However, the sensor with ultra-low concentration sensitivity is not suitable for the direct detection of high concentration of glucose in human serum and food samples. Additionally, the application of ratiometric fluorescence probe is usually limited by the narrow range of color changes and insensitivity color change of the target. Here, a novel dual-emission ratiometric fluorescence probe with green to red fluorescence intensity of 6:1 was first constructed by fluorescein isothiocyanate (FITC) with green fluorescence as signal unit and silica coated quantum dot (QD@SiO 2 ) with red fluorescence as the stable internal standard. The glucose was oxidized to generate H 2 O 2 by the catalysis of glucose oxidase , which can oxidize Fe 2+ to form Fe 3+ ion. The formation of Fe 3+ ion will cause the quenching of FITC fluorescence, which can realize the continuous fluorescence color change from green to yellow to orange to red for the qualitative and quantitative detection of blood glucose and fruit juice. The proposed method is cheap, simple, intuitive and has a wide detection range for glucose detection, which is of significance in designing the dual-emission ratiometric fluorescence sensor with wide range of color change.