Carbon dots encapsulated in (YGd)2O3:Eu3+ nanophosphors for thermal sensing, advanced forensic and information security applications

Abstract

The outstanding optical characteristics of carbon dots (CDs) make them an extremely promising class of multifunctional nanomaterials based on carbon. The incorporation of hydrothermally prepared Aloe vera carbon dots (AVCDs) into europium doped yttrium gadolinium ((YGd)2O3:Eu3+) mixed oxide nanophosphors ((YGO):Eu3+ NPs) synthesized through the solution combustion (SC) method. The resulting (YGO):Eu3+@AVCDs nanocomposite (NCs) demonstrates a broad excitation band, with the intense peak at ∼395 nm, aligning with the emission wavelength (350–420 nm) of n-UV LED chips. Notably, the (YGO):Eu3+@AVCDs (5 wt %) NCs exhibits a 4 fold increase in photoluminescence (PL) intensity compared to (YGO):7Eu3+, attributed to the fluorescence resonance energy transfer (FRET) between AVCDs and Eu3+ ions. Remarkably, even at an elevated temperature of 423 K, the thermal stability of (YGO):Eu3+@AVCDs (5 wt %) remains exceptional, retaining 88.31 % of its initial luminescence intensity. The internal quantum efficiency (IQE) is measured at a notable 74.16 %, while the optimized composite achieves a remarkable color purity of 99.59 %. Latent fingerprints (LFPs) are effectively developed on different surfaces using the optimized NCs via a simple powder dusting technique, and these fingerprints (FPs) revealed under 365 nm UV light. The study also examines various pore parameter namely size, shape, number, position, type, and inter-distance. Moreover, a transparent anti-counterfeiting (AC) ink is fabricated using optimized NCs providing effective AC features through its red emission under 365 nm UV light. This study not only offers solutions for overcoming the self-quenching effect of CDs but also underscores the potential applications in white light emitting diodes (w-LEDs), latent fingerprints, lip prints (LPs), and anti-counterfeiting.