Facile preparation of holmium(III)-doped carbon nanodots for fluorescence/magnetic resonance dual-modal bioimaging

Holmium(III)-doped carbon nanodots (HoBCDs) were synthesized for the first time via hydrothermal treatment of citrate acid (CA), branched-polyethylenimine (BPEI) and diethylenetriamine pentaacetic acid hydrate holmium(III) dihydrogen salt (Ho-DTPA), and their dual-modality bioimaging applications were demonstrated by the use of HeLa cells. The as-prepared nanoprobes exhibited bright fluorescence with an absolute quantum yield of 8% and apparent contrast enhancement in T1-weighted images.