An Improved Synthesis of Water-Soluble Dual Fluorescence Emission Carbon Dots from Holly Leaves for Accurate Detection of Mercury Ions in Living Cells.

BACKGROUND

Carbon dots (CDs) emitting near-infrared fluorescence were recently synthesized from green leaves. However, the Hg detection of CDs was limited because of the insufficient water solubility, low fluorescence and poor stability.

METHODS

Dual fluorescence emission water-soluble CD (Dual-CD) was prepared through a solvothermal method from holly leaves and low toxic PEI. PEG was further grafted onto the surface to improve the water solubility and stability.

RESULTS

The Dual-CD solution can emit 487 nm and 676 nm fluorescence under single excitation and exhibit high quantum yield of 16.8%. The fluorescence at 678 nm decreased remarkably while the emission at 470 nm was slightly affected by the addition of Hg. The ratiometric Hg detection had a wide linear range of 0-100 μM and low detection limit of 14.0 nM. In A549 cells, there was a good linear relation between F/F and the concentration of Hg in the range of 0-60 μM; the detection limit was 477 nM. Furthermore, Dual-CD showed visual fluorescence change under Hg.

CONCLUSION

Dual-CD has ratiometric responsiveness to Hg and can be applied for quantitative Hg detection in living cells.