One‐Step Synthesis Nitrogen‐Doped Multicolor Fluorescent Carbon Dots: Full Color LEDs and Fingerprint Detection Applications

Abstract Multicolor carbon dots (CDs) have emerged promising fluorescent nanomaterials and their unique fluorescence properties have been widely studied in the field of optoelectronics. However, there are still great challenges in preparing fluorescently tunable multicolor CDs that work stably in the visible spectrum. In this work, multicolor CDs were prepared using low‐cost citric acid and urea as the main precursors through a simple one‐step solvothermal method. Red, green, and blue fluorescent CDs (R‐CDs, G‐CDs, and B‐CDs) with stable optical properties were prepared by changing the solvent to N, N‐dimethylformamide, ethanol, and water, respectively. Multicolor CDs achieved full coverage of fluorescence emission wavelengths from short to long wavelength, with QY values of 5.87%, 13.18%, and 15.89%. The analysis of the chemical structure and optical properties of the multicolor CDs showed that the fluorescence mechanism was mainly attributed to the C═O content (4.90%, 7.65% and 8.26% for R‐CDs, G‐CDs, and B‐CDs), different proportions of pyrrolic N (4.95%, 4.32% and 3.47% for R‐CDs, G‐CDs, and B‐CDs, respectively) and the degree of graphitization causing a redshift in the emission wavelength. Finally, based on the polymer matrix multicolor luminescence properties of CDs, the application of multicolor light‐emitting diodes (LEDs) devices and latent fingerprint detection (LFP) was achieved.