Revealing a Competitive and Slowed Reaction Mechanism by Using Synchrotron Radiation-Based Semi In Situ Techniques on the Structure Evolution of Functional Carbon Dots

The production of stable carbon dots in large quantities for use in industrial or clinical applications has remained a challenge, particularly with regard to the preservation of specific functional molecular groups. Synchrotron radiation-based analytical techniques have been used to study the reactions occurring during the formation of carbon dots. Based on this technique, a reaction mechanism of intramolecular competition in the hydrothermal synthesis of carbon dots was found. The competitively reactive functional groups result in slowing the rapid polymerization and carbonization and inhibiting the production of the intermediate active substance (5-hydroxymethylfurfural). This mechanism slowed and controlled the reaction, ensuring the retention of the desired functional group on the surface of the carbon dots. Through this strategy, there were significant improvements in the process capability indexes Cp and Cpk of the synthesized carbon dots, which were increased by 32% and 56%, respectively. This improvement ensures consistent granularity of the product from batch to batch, resulting in stable engineered carbon dots. In addition, functional carbon dots with a significant number of amino acid functional molecules could be produced by this mechanism, which can be specifically taken up by tumor cells via amino acid and glucose transporters, meaning that these carbon dots have the potential for clinical transformation.