Separation of carbon quantum dots on a C18 column by binary gradient elution via HPLC
Carbon quantum dots (CQDs) have attracted significant attention due to their low toxicity, biocompatibility and potential applications, particularly in the field of biomedical imaging. However, the major drawback limiting the application of CQDs is their relatively low quantum yield (QY). For further study and applications of CQDs, this class of carbon nanomaterials requires separation and purification. In this paper, we report a general method to separate CQDs obtained using resorcinol (m-C6H6O2) as the carbon precursor on a C18 column through high performance liquid chromatography (HPLC). The separation of CQDs was achieved by binary gradient elution using acetonitrile–water and acetonitrile–methanol as the mobile phases and acetonitrile plays an important role in the separation of CQDs. The resolution of some peaks improved when the flow rate was increased; however, the separation of certain other peaks worsened, almost disappearing at higher flow rates. The characterization of the collected fractions revealed that the oxygen-containing functional groups on the CQDs are crucial when separating the CQDs through this method. Our method is feasible and the collected purified CQDs have QY as high as 0.72.