Synthesis of highly efficient green emissive carbon dots towards UV encryption fluorescent ink

Blue and red emitting carbon dots (CDs) have attracted extensive research interests, while the research on green emissive CDs (G-CDs) are often ignored. In this work, G-CDs with high photonluminescence quantum yield (PLQY) were synthesized through a microwave assisted solvothermal method, where 1-amino-2-naphthol-4-sul-fonic acid (ANSA) and ethylenediamine were used as precursors, and ethanol as solvent. The chemical structure, surface composition and optical properties of G-CDs suggest that the G-CDs have a structure of carbon core coated by functional groups such as hydroxyl, sulfinyl, and amino groups. The mass fractions of C, N, O and S elements are 75.83%, 14.26%, 9.31% and 0.8%, respectively. The excitation and emission wavelengths are 439 nm and 528 nm, respectively. The G-CDs have considerable photonluminescence efficiency with QY up to 33.8%, which exceeds those of many other G-CDs. The G-CDs exhibit excitation wavelength-independent emission behavior, indicating that they possess a unique PL center. Furthermore, the possible synthesis mechanism and a simple application of the G-CDs are briefly introduced. This work is of great value for filling the gap of G-CDs with high PLQY and promoting the practical application of CDs.