Ln₂O₃:Eu nanoparticles: host lattices and their impact on photoluminescence, Raman, optical, and crystal properties

A comparative spectral analysis was performed to investigate the impact of the host lattice on crystal phase, crystallinity, thermal properties, Raman shift, optical bandgap, surface behavior, and luminescent properties of the as-prepared La₂O₃:Eu, Gd₂O₃:Eu, and Y₂O₃:Eu nanoparticle(NPs). X-ray diffraction pattern (XRD) outcome shows the influence of the host matrix in identical formulae but the different crystal phases with an average size 15, 12, and 18 nm, respectively. X-ray photoelectron spectroscopy (XPS), transmission electron microscopy, and dynamic light scattering methods were exploited to determine the size, valence states, and size distribution of the samples. UV/visible spectra were measured in an aqueous solution to quantify the colloidal stability and optical characteristics of the samples. Energy bandgap values were calculated from the absorption spectra for the three different metal oxides. The laser-excited Raman spectra show abundant Raman active peaks because of the presence of the dopant ions. Based on the lattice constants of each metal oxide sample, the existence of a very prominent peak in the region of 320–420 cm⁻¹ defines in all three Raman spectra. As the unit cell parameters rise, the frequency of this peak declines in intensity, making the structure less robust. Hexagonal phase La₂O₃:Eu NPs exhibited strong multiple emission transitions in the visible region, whereas cubic phase Gd₂O₃:Eu and Y₂O₃:Eu NPs illustrated most strong red emission transition located at 611 nm which correspond to the ⁵D₀ → ⁷F₂ under excitation from the same 325-nm wavelength. The proposed results are highly applicable in the development of photonic base applications and quantify the doping concentrations in the host lattices.