Fluorescent carbon dots for sensitive determination and intracellular imaging of zinc(II) ion

We describe the preparation of carbon dots (CDs) from glucose that possess high stability, a quantum yield of 0.32, and low toxicity (according to an MTT assay). They were used, in combination with the fluorogenic zinc(II) probe quercetin to establish a fluorescence resonance energy transfer (FRET) system for the determination of Zn(II). The CDs are acting as the donor, and the quercetin-Zn(II) complex as the acceptor. This is possible because of the strong overlap between the fluorescence spectrum of CDs and the absorption spectrum of the complex. The method enables Zn(II) to be determined in the 2 to 100 μM concentration range, with a 2 μM detection limit. The method was applied to image the distribution of Zn(II) ions in HeLa cells.

Based on the fluorescence resonance energy transfer (FRET) between carbon dots and quercetin (QCT)-Zn²⁺, the fluorescence indicator was established, which displays high sensitivity and selectivity in the detection of Zn²⁺. The method was also applied to image the distribution of Zn(II) ions in HeLa cells.