Lanthanide luminescence sensitization via SnO2 nanoparticle host energy transfer

Abstract

Using a sol-gel synthesis method, nanoparticles of SnO 2 doped by a range of lanthanide ions (Ln 3+) were produced. The UV-visible photoluminescence (PL) emission and excitation spectra were analyzed. Upon excitation of the host oxide at energies above its fundamental bandgap, efficient sensitization of PL emission of all the lanthanide ions was observed. The effects of the Ln 3+ concentrations and ionic radii on the spectra were discussed and interpreted in terms of likely mechanisms of host-guest energy transfer.

Correlation between Structural Studies and the Cathodoluminescence of Individual Complex Niobate Particles

“…It is worth mentioning here that according to ref , multiple sites exist in the lattice of lanthanide-doped materials, which were studied by the visible emission bands of the Ln 3+ . For example, after investigating the local structure around the Ln 3+ dopants, it was found that Ln 3+ ions enter the ABNbO 3 structure with A and B being alkali and alkaline earth metals not only by substituting A and B but also by substituting Nb lattice positions .…”

“…Depending on which site Ln 3+ ions occupy, different transitions can be achieved. − If the active ions occupy the site with C 2 symmetry (RE sites), which leads to the removal of the parity-forbidden f–f transition, a higher intensity can be observed . Magnetic-dipole transitions are independent of site symmetry, whereas electric-dipole ones are only allowed at sites of low symmetry with no inversion center . Therefore, the high intensity of some peaks indicates that a significant proportion of the Pr 3+ is located in noncentrosymmetric sites, whereas broad emission lines are related to the lower incorporation of Pr 3+ ions into the crystal lattice …”

“…Magnetic-dipole transitions are independent of site symmetry, whereas electric-dipole ones are only allowed at sites of low symmetry with no inversion center . Therefore, the high intensity of some peaks indicates that a significant proportion of the Pr 3+ is located in noncentrosymmetric sites, whereas broad emission lines are related to the lower incorporation of Pr 3+ ions into the crystal lattice …”

“…The Judd-Ofelt theory explains how the crystal field perturbates the orbitals of the lanthanide ion. This perturbation causes mixing of the orbitals with different parities, and as a result, the forbidden f–f transition become partially allowed. − To achieve emission spectra with high intensity and sharp emission lines, different factors such as doping concentration, the ionic radii mismatch to the host, and different lattice sites for the lanthanide ions have been investigated. , Morais Faustino et al have shown that increasing the doping concentration of Eu 3+ to a certain amount optimizes the emission intensity. However, increasing the concentration more than the optimum amount leads to emission quenching, which is caused by nonradiative energy transfer between Eu 3+ ions.…”

“…However, increasing the concentration more than the optimum amount leads to emission quenching, which is caused by nonradiative energy transfer between Eu 3+ ions. The optimum concentration of Eu 3+ dopants changes remarkably with the type of host material, synthesis conditions, etc . Furthermore, the authors suggest that due to the mismatch of ionic radii, the doping mechanisms play a crucial role for the formation of defects within the host.…”