New Observations on Concentration‐Regulated Carbon Dots

Carbon dots have many new and interesting phenomena and the concentration‐dependent luminescence wavelength is an intriguing one. Luminescent carbon dots have recently gained interest due to their new and interesting phenomena such as its concentration‐dependent peak emission. While there have been reports and discussions on this phenomenon, the mechanism continues to be poorly understood. Herein, new observations on nitrogen–sulfur codoping carbon dots (NSCDs) diluted at different concentrations show that the high concentration of G‐NSCDs (0.2 mg mL−1) emits green fluorescence while the low concentration of B‐NSCDs (0.01 mg mL−1) emits blue fluorescence. It is found that the carbon dot size changes with the particle concentration: the high concentration of G‐NSCDs is about 37 nm in size while the low concentration of B‐NSCDs is only about 1.8 nm in size. Therefore, it is clearly demonstrated that the emission wavelength is related to the particle size. These interesting behaviors open a door for the exploration of new materials with novel potential.