Luminescent and optical thermometric behavior of Sm3+ activated LaOBr nanophosphors for display applications and visualization of latent fingerprints.

This study investigates the structural and optical properties of Sm3+ doped LaOBr nanophosphors, which were successfully synthesized using a facile solid-state reaction method. The X-ray diffraction (XRD) patterns and Rietveld refinement confirmed that the developed sample shows a tetragonal crystal structure with the space group P4/nmm. X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, Transmission Electron Microscopy (TEM), and Field Emission Scanning Electron Microscopy (FESEM) clearly validated the elemental composition, chemical bonds, and morphology of the synthesized sample. Photoluminescence (PL) spectra revealed the emission of orange-red light from the samples and the impact of dopant concentration quenching. The photoluminescence performance is theoretically compared with calculated Judd-Ofelt parameters and follows the trend (Ω2 > Ω4 > Ω6). The analysis of temperature-dependent photoluminescence and thermal sensing behavior of the material is carried out using two effective optical techniques: Fluorescence Intensity Ratio (FIR) thermometry and Full Width at Half Maximum (FWHM) thermometry. The potential applications of these nanophosphors are greatly enhanced by their remarkable properties, which can be utilized in the development of latent fingerprints, lip prints, and security label patterns. The findings suggest that the orange-red luminescent LaOBr: Sm3+ nanophosphor is a promising candidate for both display applications and forensic detection analysis.