LAUSR

Abstract In this work, we report the synthesis of holmium(III)-doped carbon nanodots (HoBCDs) as fluorescence/magnetic resonance (FL/MR) dual-modal imaging probes via a facile hydrothermal process using citrate acid (CA), branched-polyethylenimine (BPEI) and diethylenetriamine pentaacetic acid hydrate holmium(III) dihydrogen salt (Ho-DTPA) as carbon source, passivating reagent and holmium source, respectively. The thus prepared HoBCDs exhibited ultra-small particle size (∼4 nm), high water solubility and bright fluorescence with an absolute quantum yield of 8%. Additionally, grey-scaled T1-weighted images of HoBCDs solution appeared to be apparently brighter than that of deionized water and un-doped blue carbon nanodots (BCDs) solution. In addition, in vitro toxicity assay validated superior biocompatibility of HoBCDs. Using HeLa cells as models, HoBCDs-treated cells were observed to emit blue fluorescence located both in plasma and nucleus, and presented positive contrast enhancement in T1-weighted images, suggesting their potentials for practical biomedical applications.