Rational Design of Ultrahigh Stability Carbon Dot-Based Composites for Anticounterfeiting and W-LED Applications

Carbon dots (CDs) with room-temperature phosphorescence (RTP) properties have been widely applied in various fields. However, achieving multicolor phosphorescence with high stability remains a significant challenge. In this study, a simple synthetic strategy was developed to prepare RTP CDs composites (CDs@SiO2–Urea) by using trimesic acid (TMA) as the carbon source, with urea and (3-aminopropyl)triethoxysilane (APTES) serving as a coconstructed rigid matrix. CDs@SiO2–Urea exhibits bright blue RTP after UV light is turned off, with a lifetime of 406 ms and visible to the naked eye for 6 s. Notably, owing to the synergistic protective effect of the urea and APTES matrices, CDs@SiO2–Urea demonstrates high stability in water, organic solvents, and strong acidic and alkaline environments while still maintaining excellent RTP properties. Additionally, based on the Förster resonance energy transfer (FRET) mechanism, brilliant green (BG), rhodamine 6G (Rh6G), and rhodamine B (RhB) were introduced to the CDs@SiO2–Urea system, successfully achieving green, yellow, and red multicolor fluorescence and phosphorescence emission. Finally, utilizing the unique optical properties of the prepared samples, the materials were successfully applied to anticounterfeiting encryption and white light-emitting diode (W-LED) devices. These devices maintain high luminance intensity and a stable color rendering index (CRI) during long-time operation, highlighting the strong potential of RTP CD composites for commercial applications.