Differences in the performance of broad-spectrum UV-absorbing carbon dots arising from diverse purification

Excessive ultraviolet radiation gradually affects human health, the growth of animals or plants and the stability of materials with the deterioration of global climate. In this paper, we used aromatic compounds to prepare the three-component water soluble carbon dots (Im-CDs) through the hydrothermal method, which has broadspectrum ultraviolet (UV) absorption. However, the stability of CDs with UV absorption still presents certain challenges. It was found that the bottom-up synthesis of CDs generally results in the production of small molecular or oligo-fluorescent by-products. Inadequate purification can lead to misinterpretation of their properties and characteristics. Therefore, the prepared CDs were purified using conventional dialysis, prolonged dialysis, and silica gel column chromatography to compare the effects and errors of different purification methods on the results. Based on the resulting purification process, the structure model of the Im-CDs suggested that the carbon core possesses a core-shell structure along with weakly attached ligands on its surface rather than strong force. After chromatography, the Im-CDs had better heat, UV and acid-base resistance compared to other purification methods. The appropriate purification for CDs is therefore a crucial step in order to fulfill the prerequisites for practical applications. This is of great significance for the industrialization of CDs.