Dual-mode fluorometric and colorimetric sensor based on carbon quantum dots-doped MIL-53(Fe) encapsulated in SiO2 shells for fluoride detection

Abstract

Fluoride (F⁻) is widely distributed in nature, but its excessive discharge into the environment can lead to severe ecological and health problems. Therefore, it is of very great significance to develop sensitive and accurate methods for F⁻ detection. Herein, a dual-mode fluorometric and colorimetric sensor based on MIL-53(Fe)-CQDs@SiO₂ is synthesized using a step-by-step self-assembly method. Notably, the introduced carbon quantum dots (CQDs) accelerate the charge transfer and activate the intrinsic active sites of MIL-53(Fe), thereby enhancing the peroxidase-like activity of MIL-53(Fe). Meanwhile, CQDs as a functional group can also impart fluorescence ability to MIL-53(Fe), and the outer SiO₂ acts as the start switch controlling the peroxidase-like activity and fluorescence of MIL-53(Fe)-CQDs@SiO₂. Benefiting from the peroxidase-like activity and fluorescence ability of MIL-53(Fe)-CQDs@SiO₂, a feasible and effective fluorometric and colorimetric dual-mode analytical method for the specific detection of F⁻ is established. The combination of two analytical platforms improves the accuracy and reliability of the detection method. As expected, both the fluorometric and colorimetric analytical methods exhibit broad linear ranges and low limits of detection, demonstrating the excellent application potential for the detection of F⁻. Furthermore, mechanistic analysis suggests that SiO₂ acts as the recognition site and is etched by F⁻, thus influencing the absorbance and fluorescence of the system. All in all, the current work provides a sensitive and reliable method for detecting F⁻.