Efficient Bioimaging Using Rare-Earth-Doped Carbon Quantum Dots: A Doping Strategy - data

Carbon quantum dots (CQDs) are promising biomaterials due to their biocompatibility, water solubility, and imaging capabilities. However, their bioimaging application is constrained by low photoluminescence quantum yield (PLQY) and low production due to complex purification. This study developed lanthanide-doped CQDs (L-CQDs) via a microwave-assisted solvothermal method in a glycerol–water system to enhance fluorescence and simplify purification. Optimal synthesis was achieved with a mass ratio of citric acid monohydrate : urea : NdCl₃·6H₂O : CeCl₃ at 30:3:10:2 and glycerol/water volume ratio of 2:1. A one-pot synthesis of carbon quantum dots was firstly presented using two biocompatible elements, cerium and neodymium. The incorporation of rare-earth elements significantly enhanced biofluorescence imaging performance, from 0.43% to 69%. The resulting L-CQDs exhibited a graphene-like structure (~8 nm) and a high PLQY of 69% at 440 nm emission. Anti-Stokes blue emission was observed under 740 and 800 nm excitation. Ethanol precipitation enabled straightforward purification, indicating surface modification with hydrophobic groups post-doping. The L-CQDs demonstrated excellent biosafety in HUVEC cells, RAW264.7 cells and C57 mice, and showed enhanced fluorescence intensity compared to undoped CQDs. They effectively accumulated in highly perfused organs including the brain, lungs, spleen, and kidneys, and were capable of crossing the blood–brain barrier. These findings indicate that L-CQDs are promising for bioimaging applications such as cellular labeling and selective in vivo fluorescence imaging.