Exploring the structural and luminescent properties of Eu3+ activated LaOBr nanophosphors for potential lighting, optical thermometry and forensic applications

Abstract

The milestone significance of red-emitting phosphor has channeled the synthesis of high-luminous LaOBr: Eu³⁺ nanophosphors through a solid-state route. The comprehensive phase purity and crystal structure characterizations are performed using X-ray diffraction (XRD) and Rietveld refinement analysis. The elemental composition, morphology and the incorporation of Eu³⁺ in LaOBr matrix are substantiated using X-ray photon electron spectroscopy (XPS), TEM, FESEM and EDS techniques. The radiative properties were evaluated using Judd-Ofelt analysis, and the JO parameters follow the trend Ω₂ > Ω₄. The photoluminescence spectrum exhibits deep red emission at 618 nm and the sample at 5 mol% is determined to be the optimized concentration, through dipole-dipole interaction. The decay lifetime is found to be the order of microseconds and the calorimetric investigation, gives insights about CIE coordinates (0.6304, 0.3692), CCT (1186 K) and LER (182 lm/W) of the optimum concentration. The optimized phosphor exhibited good thermal stability and activation energy is evaluated. The FIR and FWHM modes are utilized to calculate the absolute and relative sensitivities of the optimized phosphor material. Impressively, the scope of these nanophosphors was leveraged to detect latent fingerprints (LFP), lip prints and for the fabrication of flexible luminescent inks with excellent sensitivity and resolution. This study showcases LaOBr: Eu³⁺ as a versatile luminous platform for applications in WLEDs, optical thermometry, forensic science, flexible displays and anti-counterfeiting.