Abstract: In an attempt to investigate the effect of different solvent purification on the properties ofRhodiola crenulatecarbon dots, in this study,Rhodiola crenulatewater-soluble carbon dots (RWW-CDs) andR.crenulatealcohol-soluble carbon dots (RWE-CDs) were prepared by hydrothermal carbonization ofR.crenulatepowder of the Tibetan medicine at high temperatures, which were then separated and purified. TEM, UV-visible spectroscopy, fluorescence spectroscopy, FTIR, XPS, and XRD comparative analyses were used to compare the characterization data ofR.crenulate-CDs prepared by the two different methods. The dimension of RWE-CDs was found to be larger than that of RWW-CDs, and the fluorescence properties of the twoR.crenulatecarbon dots were good, but the fluorescence properties of RWW-CDs were better than that of RWE-CDs. The result of XPS demonstrated that the main components of the twoR.crenulatecarbon dots were carbon, oxygen, and nitrogen, moreover, the content of nitrogen in the RWW-CDs was extremely low and the content of carbon was higher than that in the RWW-CDs. XRD results demonstrated that the twoR.crenulatecarbon dots prepared by this paper were characterized by a combination of the following factors. The crystalline phases of the twoR.crenulatecarbon dots prepared in this paper were consistent with the {10.0} plane of CQD, but the characteristic peaks of RWE-CDs were better than those of RWW-CDs. The Fourier infrared spectroscopy showed that the peaks of the RWW-CDs were more uniform and stable, while the RWE-CDs had more miscellaneous peaks, which might be due to the difference of solvents used for the two carbon dots extraction. The CCK-8 method and Calcein/PI staining method were also used to determine that there was no significant difference in biological toxicity between theR.crenulatecarbon dots purified by the two methods. Furthermore, the pH fluorescence stability and cellular imaging of the two carbon dots were also explored.

Key words: Tibetan medicineRhodiola crenulata, carbon dots, TEM, XRD, XPS