In-situ embedding of carbon dots in perovskite GdAlO3:Eu3+/Li+ composite: Boosting phosphor stability, optical thermometry, flexible displays and data protection applications

Abstract

Phosphors that are highly fluorescent have shown considerable promise in applications like flexible displays and enhancing data security. Still, the task of boosting their fluorescence attributes, especially in the realm of phosphors, remains an ongoing challenge. Precisely, the luminescent properties of GdAlO3:Eu3+ (GAO:Eu3+) phosphors co-doped with lanthanide (Ln) and alkali ions (M+) are successfully synthesized using a solution combustion method. The integration of fluorescent carbon dots (CDs) onto the GAO:7Eu3+/Li+ phosphor surface notably enhanced their luminescent characteristics. Incorporating CDs into GAO:7Eu3+/Li+ resulted in a decrease in both positive and negative defects within the phosphor, consequently enhancing its crystalline structure. Particularly noteworthy is the substantial spectral alignment observed between the emission of CDs and the absorption of GAO:7Eu3+/Li+. When excited by 395 nm UV light, the GAO phosphors displayed the distinctive emission associated with the doping ions. The emission intensity of GAO:7Eu3+/Li+, and CDs(7 wt%)@GAO:7Eu3+/Li+ composite rises by 18 and 66.23 folds, respectively, in comparison to the corresponding samples lacking the inclusion of CDs. The enhanced photoluminescence (PL) intensity observed can be attributed to the Förster resonance energy transfer (FRET) mechanism. In comparison to its emission intensity at room temperature, the CDs@GAO:7Eu3+/Li+ composite retains 95.6% of its intensity, while GAO:7Eu3+ retains 88.5% and GAO:7Eu3+/Li+ retains 91.2% at 400 K, showcasing remarkable thermal stability. The finely optimized CDs(7 wt%)@ GAO:7Eu3+/Li+ combination displays an impressive color purity (CP) of 98.15 %. Furthermore, this NCs demonstrates significant potential for optical thermometry across a broad temperature spectrum ranging from 300 to 480 K. The brush mode is utilized to create anti-counterfeiting (AC) labels using the optimized composite ink on various surfaces. The resulting AC tags exhibit high resolution and durability. The fabricated flexible films exhibit remarkable flexibility, and foldability significantly broaden the scope of potential applications in the field of AC. These results suggest that CDs(7 wt%)@ GAO:7Eu3+/Li+ have potential for multifaceted applications in flexible luminescent films, AC, and optical thermometry.