Efficient bioimaging using rare-earth-doped carbon quantum dots: A doping strategy

This study addressed the limitations of carbon quantum dots (CQDs) in bioimaging, specifically low photoluminescence quantum yield (PLQY) and complex purification processes, by developing lanthanide-doped CQDs (L-CQDs). Using a microwave-assisted solvothermal method in a glycerol-water system with precursor mass ratios of citric acid monohydrate: urea: NdCl₃·6H₂O:CeCl₃ at 30:3:10:2 and a glycerol/water volume ratio of 2:1, we achieved one-pot synthesis with cerium and neodymium doping. This approach significantly enhanced the PLQY from 0.43% to 69%. The resulting L-CQDs exhibited a graphene-like structure (≈8 nm) and demonstrated anti-Stokes blue emission under 740 and 800 nm excitation. Besides, ethanol precipitation facilitated purification and indicated surface hydrophobicity post-doping. The materials showed excellent biosafety in HUVEC cells, RAW264.7 cells, and C57 mice, with enhanced fluorescence intensity and specific accumulation in highly perfused organs, including the brain, lungs, spleen, and kidneys, while demonstrating blood-brain barrier penetration capability. These findings highlighted the potential of L-CQDs for cellular labeling and in vivo fluorescence imaging applications.