A new type of self-targeting carbon dot (CD-Fla) for the detection of the toxic heavy metal ion Pb²⁺ was synthesized via a one-pot hydrothermal route using flavonoid extracts of Ginkgo biloba leaves as the starting material. As-prepared CD-Fla exhibited excellent biocompatibility and strong blue emission with a quantum yield of 16.1% and significant fluorescence quenching selectivity for Pb²⁺ without using any additional targeting molecules. CD-Fla could detect Pb²⁺ quantitatively within the range 0.1–20.0 nM, with an ultrahigh sensitivity of 55 pM. The selectivity of CD-Fla for Pb²⁺ was nearly one order of magnitude higher than that for other relevant metal ions. This was much better than ever reported CD-based metal ion sensors. The high sensitivity and selectivity were due to the incorporation of certain flavonoid-like moieties into CD-Fla. CD-Fla was also demonstrated to be a good probe for fluorescence tracing of intracellular Pb²⁺. The capability of CD-Fla was further improved when it was doped on agarose hydrogel. CD-Fla-doped agarose hydrogel (CD-AHG) allowed for visual fluorescence detection and removal of Pb²⁺ from water. This was confirmed by testing CD-AHG in actual water samples taken from the Jialing River (Chongqing, China). The Pb²⁺ adsorbed CD-AHG was regenerable in HCl solution. This study will open a new avenue for synthesizing intelligent materials capable of simultaneously targeting, detecting, and treating heavy metal ions.

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