Broadband Luminescence in Rare Earth Doped Sr2SiS4: Relating Energy Levels of Ce3+ and Eu2

Explanation for the Multi-Component Scintillation of Cerium Fluoride Through the Equilibrium and Photophysical Investigation of Cerium(III)-Fluoro Complexes

CeF₃ displays favorable scintillation properties, which have been utilized for decades in various solid-state systems. Its emission undergoes multi-component decays, which were interpreted by lattice defects and so-called intrinsic features herein. This study of the complex equilibria in connection with photophysical behavior of the cerium(III)-fluoride system in solution gave us the possibility to reveal the individual contribution of the [Ce^IIIF_x(H₂O)_9−x]^3−x species to the photoluminescence. Spectrophotometry and spectrofluorometry (also in time-resolved mode) were used, and combined with sophisticated evaluation methods regarding both the complex equilibria and the kinetics of the photoinduced processes. The individual photophysical parameters of the [Ce^IIIF_x(H₂O)_9−x]^3−x complexes were determined. For the kinetic evaluation, three methods of various simplifications were applied and compared. The results indicated that the rates of some excited-state equilibrium processes were comparable to those of the emission decay steps. Our results also contribute to the explanation of the multi-component emission decays in the CeF₃-containing scintillators, due to the various coordination environments of Ce³⁺, which can be affected by the excitation leading to the dissociation of the metal-ligand bonds.

Luminescent Lanthanide MOFs: A Unique Platform for Chemical Sensing

In recent years, lanthanide metal-organic frameworks (LnMOFs) have developed to be an interesting subclass of MOFs. The combination of the characteristic luminescent properties of Ln ions with the intriguing topological structures of MOFs opens up promising possibilities for the design of LnMOF-based chemical sensors. In this review, we present the most recent developments of LnMOFs as chemical sensors by briefly introducing the general luminescence features of LnMOFs, followed by a comprehensive investigation of the applications of LnMOF sensors for cations, anions, small molecules, nitroaromatic explosives, gases, vapors, pH, and temperature, as well as biomolecules.

Efficient multicolor tunability of ultrasmall ternary-doped LaF3 nanoparticles: energy conversion and magnetic behavior

Luminescence-tunable multicolored LaF₃:xCe³⁺,xGd³⁺,yEu³⁺ (x = 5; y = 1, 5, 10, and 15 mol%) nanoparticles have been synthesized via a low cost polyol method. Powder X-ray diffraction and high-resolution transmission electron microscopy studies confirm the hexagonal phase of the LaF₃:xCe³⁺,xGd³⁺,yEu³⁺ nanophosphors with average sizes (oval shape) ranging from 5 to 7 nm. Energy-dispersive X-ray spectroscopy analyses show the uniform distribution of Ce³⁺, Gd³⁺, and Eu³⁺ dopants in the LaF₃ host matrix. The photoluminescence spectra and electron paramagnetic resonance measurements guarantee the presence of Eu²⁺, corroborated through DC susceptibility measurements of the samples displaying paramagnetic behavior at 300 K, whereas weak ferromagnetic ordering is shown at 2 K. The non-radiative energy transfer processes from the 4f(²F_5/2) → 5d state (Ce³⁺) to the intraconfigurational 4f excited levels of rare earth ions and simultaneous emissions in the visible region from the 4f⁶5d¹ (Eu²⁺) and ⁵D₀ (Eu³⁺) emitting levels, leading to overlapped broad and narrow emission bands, have been proclaimed. The energy transfer mechanism proposes involvement of the Gd³⁺ ion sub-lattice as the bridge and finally trapping by Eu^2+/3+, upon excitation of the Ce³⁺ ion. The calculation of experimental intensity parameters (Ω_2,4) has been discussed and the highest emission quantum efficiency (η = 85%) of the Eu³⁺ ion for the y = 10 mol% sample is reported. The advantageous existence of the Eu²⁺/Eu³⁺ ratio along with variously doped nanomaterials described in this work, results in tunable emission color in the blue-white-red regions, highlighting the potential application of the samples in solid-state lighting devices, scintillation devices, and multiplex detection.

Optical, Structural and Paramagnetic Properties of Eu-Doped Ternary Sulfides ALnS₂ (A = Na, K, Rb; Ln = La, Gd, Lu, Y)

Eu-doped ternary sulfides of general formula ALnS₂ (A = Na, K, Rb; Ln = La, Gd, Lu, Y) are presented as a novel interesting material family which may find usage as X-ray phosphors or solid state white light emitting diode (LED) lighting. Samples were synthesized in the form of transparent crystalline hexagonal platelets by chemical reaction under the flow of hydrogen sulfide. Their physical properties were investigated by means of X-ray diffraction, time-resolved photoluminescence spectroscopy, electron paramagnetic resonance, and X-ray excited fluorescence. Corresponding characteristics, including absorption, radioluminescence, photoluminescence excitation and emission spectra, and decay kinetics curves, were measured and evaluated in a broad temperature range (8-800 K). Calculations including quantum local crystal field potential and spin-Hamiltonian for a paramagnetic particle in D3d local symmetry and phenomenological model dealing with excited state dynamics were performed to explain the experimentally observed features. Based on the results, an energy diagram of lanthanide energy levels in KLuS₂ is proposed. Color model xy-coordinates are used to compare effects of dopants on the resulting spectrum. The application potential of the mentioned compounds in the field of white LED solid state lighting or X-ray phosphors is thoroughly discussed.

Energy level modeling of lanthanide materials: review and uncertainty analysis

Empirical energy level models for describing lanthanide materials are reviewed and situated in a broader theoretical framework. The accuracy of determining experimental quantities through modeling is assessed.