A magnetofluorescent boron-doped carbon dots as a metal-free bimodal probe.

High-resolution observation of biological process is vital for biological researches and diagnosing diseases, which requires accurate diagnosis that involves coordinating imaging technologies such as fluorescence and magnetic resonance (MR). Nowadays, metal-based labels have been used for dual modality imaging. However, heavy metal ions are not environment-and organism-friendly. Therefore, it is a desirable to fabricate a metal-free label with fluorescence and MR properties. Herein, we synthesized boron-doped carbon dots (B-CDs) with dual modal properties through a one-pot solvothermal process. Compared with boron-free CDs, B-CDs exhibited apparent red-shift fluoresence emission, higher fluorescence intensity, and higher longitudinal relaxivity (r1 = 5.13 mM-1 s-1). It demonstrated that boron doping can enhance the fluorescence intensity of CDs, and maybe lead to form paramagnetic centers. The fluorescence and MR imaging of B-CDs make them a prospective label for clinical applications as a result of their oversimplified synthesis process, low cost, good biocompatibility and low toxicity. It will open a new window for building novel imaging labels.