Systematic Comparison of Carbon Dots from Different Preparations—Consistent Optical Properties and Photoinduced Redox Characteristics in Visible Spectrum and Structural and Mechanistic Implications

Carbon dots (CDots) are characterized by their optical properties including strong absorptions and bright and colorful fluorescence emissions in the visible spectrum and by their photoinduced redox characteristics as both potent electron acceptors and donors. The reported study was for a systematic comparison of CDots from different synthetic approaches based on the use of pre-existing small carbon nanoparticles sourced from pure carbon soot versus the formation of similar nanoparticles in situ via a one-pot thermal carbonization of organic molecular precursors, emphasizing spectroscopic characterizations over the visible spectrum. The results show that the CDots prepared by the latter under sufficiently robust processing conditions are generally no different from those from the former in terms of the observed optical properties and associated photoinduced redox characteristics in the application-wise more meaningful visible spectral region, suggesting a high stability or general applicability of the definition on CDots as surface-passivated small-carbon nanoparticles. Implications of the reported findings to the further understanding and mechanistic explorations of CDots, including the necessity to focus on the core carbon nanoparticles in CDots in such explorations, are highlighted and discussed.