Synthesis and Photophysical Characteristics of Samarium-based Complexes for Optoelectronic and Latent Fingerprint Applications.

In this study, five orange-red color samarium (Sm(III)) complexes were prepared using a solution precipitation method, with 9,10-Difluoro-2,3-dihydro-3-methyl-7-oxo-7H-pyrido[1,2,3-de]-1,4-benzoxazine-6-carboxylic acid as the primary ligand and nitrogen-donor like 1,10-phenanthroline, 2,2-biquinoline, neocuproine, and 2,2-bipyridyl as secondary ligands. The complexes were characterized using various spectral techniques, elemental analysis CHN, energy-dispersive X-ray spectroscopy (EDX), ultraviolet-visible (UV-vis), Fourier-transform infrared (FTIR), nuclear magnetic resonance (NMR) and thermal analyses by thermogravimetric analysis (TGA), differential thermal analysis (DTA). Photoluminescence spectroscopy revealed bright orange-red emissions due to the ⁴G_5/2 → ⁶H_7/2 transition at 605 nm in solid and 598 nm in solution, with color coordinates confirming their emission in the orange region. Structural evaluations using powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM) confirmed that the complexes exhibit nanoparticle size and crystalline structure, showing their application in forensic science in latent fingerprint detection. Computational studies of highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy levels, Judd-Ofelt parameters, radiative properties, band gap, and Urbach energy indicate their potential for optoelectronic and semiconductors. The high color purity of 87.70% in solution and 77.50% in solid make them important for laser emission.