Novel Processing for Color-Tunable Luminescence Carbon Dots and Their Advantages in Biological Systems

Abstract

The novel strategy for color-tunable carbon dots (CDs) with superior dispersibility in an aqueous solution is originally proposed in a one-pot hydrothermal method. The optimized emission of resulted CDs progressively shifts from green to red with the adjustment of precursor solution from alkali to acid. The proposed three representative CDs entire green, yellow, and red fluorescences prepared separately on alkaline, neutral, and acidic aqueous solutions possess similar graphite structures in their carbon cores, while the diversification of PL emissions in these CDs are convinced to derive from the difference in their particle size and the content of nitrogen doping. Moreover, the regular variation of calculated band gaps for the three types of CDs are perfectly consistent with their PL emission characteristics. Further investigation of their radical scavenging activities based on the difference in surface states demonstrates that the CDs synthesized under alkaline conditions have stronger oxidation resistance. Thus, we can speculate that the amino groups on P-phenylenediamine precursors are more easily activated under acidic conditions, which results in an in-depth cross-linking that facilitates a long wavelength emission. In addition, the exceptional biocompatibility of these multicolored CDs enables tremendous potential applications in biological systems.