Phosphorescence approach based on silica protected carbon dots for autofluorescence interference-free and highly selective detection of fluoride

Fluoride (F−), an anion with the smallest ionic radius and highest charge density, plays an important role in biomedical and environmental processes, making the development of accurate F− detection methods of great importance. Fluorometric methods with simplicity and sensitivity have gained considerable attention in F− detection. However, their accuracy faces challenges due to issues like autofluorescence interference during real-time light excitation and limited selectivity. Therefore, it is important to establish a simple, real-time light excitation-free, and highly selective method for the accurate determination of F− in complicated samples. Herein, a novel phosphorescent approach is developed for the selective and accurate detection of F− in complex samples. Phosphorescence emission CDs@SiO2 is fabricated by confining CDs in a silica protective layer. This design retains the favorable water solubility of silica while benefitting from its inertness, making it resistant to most substances. Furthermore, phosphorescent analysis without real-time light excitation eliminates autofluorescence interference, significantly improving the signal-to-noise ratio (SNR) and simplifying sample pretreatment. The specific interaction between F− and the Si–O bond can lead to the degradation of the silica protective layer, exposing the CDs to the solution, resulting in phosphorescence quenching, achieving the highly accurate and sensitive detection of F− with a linear range of 0.001–4 mM and a limit of detection (LOD) of 1 μM. This novel F− phosphorescence method based on the metal-free phosphorescent nanomaterial CDs@SiO2 integrates the benefits of no autofluorescence interference, high selectivity, and full aqueous compatibility, and its combination with a smartphone provides a simple, portable, and cost-effective detection platform for accurate and highly sensitive determination of F− in complex samples.