Contrast medium for fluorescent-magnetic resonance dual-mode targeting biological imaging and preparation method thereof

The invention discloses a contrast medium for fluorescent-magnetic resonance dual-mode targeting biological imaging and a preparation method thereof. The method comprises the following steps that 1, a chelating agent and a compound containing Gd3+ react in water to obtain a Gd3+ chelate solution; 2, citric acid and polyethyleneimine are dissolved into water, and then the Gd3+ chelate solution is added to be mixed; 3, the mixture obtained in the step 2 is dissolved and evaporated to dryness repeatedly, centrifuging is performed on the dissolved and dried products, a supernate is taken for dialysis in water to obtain a dialysis solution, and a dialysis solution is subjected to freeze-drying, and Gd doped carbon dots are obtained. Meanwhile, the invention further discloses a contrast medium for fluorescent-magnetic resonance dual-mode targeting biological imaging. The contrast medium is synthetized in an environment-friendly mode, is low in gadolinium content, promotes surface functionalization, and has the quit