Engineering fluorescent carbon dot sensor with rare earth europium for the detection of uranium (VI) ion in vivo.

Three types of carbon dots were synthesized using the same precursor (folic acid and europium nitrate) via different preparation methods (doping and direct coordination). A comprehensive comparison and analysis of the morphology, surface groups, and optical properties of the prepared carbon dots (CD), europium-doped carbon dots (CD-Eu), and europium-functionalized carbon dots (CD@Eu) were conducted. Moreover, due to the higher quantum yield, excellent stability, and outstanding selectivity for UO22+ exhibited by CD-Eu, we selected CD-Eu as the probe for subsequent applications. CD-Eu showed a sensitive response to UO22+ within the concentration range 25 ~ 200 nM, with a detection limit of 0.84 nM (0.42 μg·L-1). Additionally, CD-Eu demonstrated excellent accuracy and recovery in spiked detection of real water samples. Furthermore, we discovered that this probe could detect UO22+ both in vitro and in vivo. This strategy provides a promising fluorescent sensor for the detection of UO22+ in water and biological samples, holding significant implications for addressing UO22+ contamination issues.