Mn, N co-doped CDs as a fluorescent nanosensing platform for the detection of tannic acid and hafnium ion and in vitro fluorescence imaging of U2OS osteosarcoma cells.

Multi-wavelength emission fluorescent manganese-nitrogen co-doped carbon dots (Mn, N co-doped CDs) were synthesized by solvothermal method using β-cyclodextrin, O-phenylenediamine, and manganese chloride as raw materials. The prepared Mn, N co-doped CDs were used as fluorescent nanosensing platforms for the detection of metal ions and biomolecules and were found to be capable of fluorescence detection of tannic acid (TA) and hafnium (Hf) ion at 320, 380, and 480 nm excitation wavelengths with multi-response linear ranges of 0.7 ~ 1.2 µM and 6.35 ~ 13 µM and detection limits of 0.45 µM and 6.3 µM, respectively. The wide linear ranges and low detection limits may be due to the fluorescence resonance energy transfer effect between the platform and TA and Hf ions. In addition, it was found that Mn, N co-doped CDs had good photostability, biocompatibility, and low cytotoxicity, which could be used for in vitro fluorescence imaging of exogenous TA and Hf ion imaging in U2OS osteosarcoma cells. Thus, the probe has a promising application in biomedical fields as a new multi-responsive fluorescence nanosensing platform member.