Fluorescent carbon dots nanosensor for label-free determination of vitamin B₁₂ based on inner filter effect

A simple and effective fluorescent assay for the determination of vitamin B₁₂ was developed. In this study, carbon dots (CDs) were prepared by one-pot hydrothermal method and directly used as a fluorophore in the inner filter effect (IFE). Both of the maximum absorption peak of vitamin B₁₂ and excitation maxima of CDs are located at 360nm, hence, the excited light of CDs can be absorbed by vitamin B₁₂, resulting in the fluorescence reduction of CDs. And the fluorescence intensity of CDs decreases with the increasing concentration of vitamin B₁₂. This IFE-based sensing strategy shows a good linear relationship between the normalized fluorescence intensity and the concentration of vitamin B₁₂ ranging from 0 to 60μM, with a limit of detection (LOD) of 0.1μM at a signal-to-noise ratio of 3. Furthermore, this proposed approach was successfully applied to vitamin B₁₂ sensing in injections. This IFE sensing platform based on various fluorescent nanomaterials has a high promise for the detection of other biomolecules due to its inherent convenience.