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 UO