Bright tunable multicolor carbon dots for white light-emitting diodes and fingerprint detection

In this study, in order to achieve high quantum yield (QY) and tunable multicolor carbon dots, the influence of quantum size effects and surface state changes were considered comprehensively. Blue-emitting seed carbon dots (S-CDs) were synthesized using 1,2,4-benzenetricarboxylic acid and urea as precursors. Green-emitting carbon dots (G-CDs) were then prepared by oxidizing S-CDs with 3 % H2O2, followed by treatment with 0.1 M NaOH to produce strong blue-emitting carbon dots (B-CDs). Compared with S-CDs, the QY of G-CDs and B-CDs increased by 35 times and 75 times, respectively. The improvement in quantum yield (QY) and the adjustment in emission wavelength were attributed to the disruption of hydrogen bonds and modifications in surface groups caused by treatments with hydrogen peroxide and sodium hydroxide. By combining B-CDs and G-CDs with commercial red phosphors, warm W-LEDs with a color rendering index as high as 91.4 and a correlated color temperature of 5437 K was successfully prepared, which was suitable for indoor lighting. In addition, B-CDs and G-CDs were used as fluorescent markers for latent fingerprints identification on different substrates, the results showed that B-CDs and G-CDs significantly enhanced the resolution of fingerprint imaging. The synthesized G-CDs and B-CDs offer several advantages, including high quantum yield, excellent photostability, low cost and a straightforward synthesis method. These properties provide a solid material foundation for enhancing the performance of white LEDs and detecting latent fingerprints.