A 3D Silverton-Type Polyoxomolybdate Based on {PrMo12O42}: Synthesis, Structure, Photoluminescence and Magnetic Properties

A three-dimensional (3D) Silverton-type polyoxomolybdate (POMo) with the formula of NH₄{Mn₄[PrMo₁₂O₄₂]}·18H₂O (1) was successfully isolated and well characterized by single crystal X-ray diffraction, X-ray powder diffraction pattern, infrared spectrum, thermogravimetric and elemental analyses. The inorganic building block {PrMo₁₂O₄₂} has formed 3D frameworks via the {MnO₆} linker. The excitation of compound 1 in solid state at 375 nm displays red emission. Moreover, variable temperature magnetic susceptibility measurements indicate that the magnetic behavior in compound 1 is dominated by antiferromagnetic interactions.

Hydrothermal Synthesis of Various Shape-Controlled Europium Hydroxides

Eu(OH)3 with various shape-controlled morphologies and size, such as plate, rod, tube, prism and nanoparticles was successfully synthesized through simple hydrothermal reactions. The products were characterized by XRD (X-Ray Powder Diffraction), FE-SEM (Field Emission- Scanning Electron Microscopy) and TG (Thermogravimetry). The influence of the initial pH value of the starting solution and reaction temperature on the crystalline phase and morphology of the hydrothermal products was investigated. A possible formation process to control morphologies and size of europium products by changing the hydrothermal temperature and initial pH value of the starting solution was proposed.

Double-Oxalate-Bridging Tetralanthanide Containing Divacant Lindqvist Isopolytungstates with an Energy Transfer Mechanism and Luminous Color Adjustablility Through Eu3+/Tb3+ Codoping

A double-oxalate-bridging tetra-Gd³⁺ containing divacant Lindqvist dimeric isopolytungtate Na₁₀[Gd₂(C₂O₄)(H₂O)₄(OH)W₄O₁₆]₂·30H₂O (Gd₄W₈) was obtained based on the reaction of Na₂WO₄·2H₂O, H₂C₂O₄, and GdCl₃ in aqueous solution. Its dimeric polyoxoanion is established by two divacant Lindqvist [W₄O₁₆]^8- segments connected by a rectangular tetra-nuclearity [Gd₄(C₂O₄)₂(H₂O)₈(OH)₂]⁶⁺ cluster. Notably, neighboring trinuclear [Na₃O₄(H₂O)₁₁]^5- clusters are interconnected to construct a picturesque 1-D sinusoidal Na-O cluster chain. The most outstanding characteristic is that 1-D sinusoidal Na-O cluster chains combine [Gd₂(C₂O₄)(H₂O)₄(OH)W₄O₁₆]₂^10- polyoxoanions together, giving rise to an intriguing 3-D extended porous framework. The red emitter Eu³⁺ ions and green emitter Tb³⁺ ions are first codoped into Gd₄W₈ to substitute Gd³⁺ ions for the exploration of the energy transfer (ET) mechanism between Eu³⁺ and Tb³⁺ ions and the color-tunable PL property in the isopolytungtate system. The PL emission spectra and decay lifetime measurements of the Eu³⁺/Tb³⁺ codoped Gd₄W₈ system illustrate that under excitation at 370 nm, Tb³⁺ ions can transfer energy to Eu³⁺ ions. When the molar concentration of Tb³⁺ ions is fixed at 0.9 and that of the Eu³⁺ ions gradually increases from 0.01 to 0.08, the calculated ET efficiency (η_ET) from Tb³⁺ to Eu³⁺ ions increases from 7.9% for Gd_0.36Tb_3.6Eu_0.04W₈ to 67.3% for Gd_0.08Tb_3.6Eu_0.32W₈. The energy transfer mechanism (Tb³⁺ → Eu³⁺) is a nonradiative dipole-dipole interaction. Furthermore, upon excitation at 370 nm, Eu₄W₈ and Tb₄W₈ show visible red- and green-emitting lights, respectively. When codoping trace amounts of Eu³⁺ ions in Tb₄W₈, under excitation at 370 nm, Tb_3.92Eu_0.08W₈ displays near white-light emission.

Tb(HSO4)(SO4) - a green emitting hydrogensulfate sulfate with second harmonic generation response

Recently, sulfates have attracted attention as materials for non-linear optical applications. This compound class is extended by Tb(HSO₄)(SO₄), which is solvothermally synthesised from Tb₄O₇ and sulfuric acid. The compound crystallises in the non-centrosymmetric space group P2₁ (Z = 2, a = 665.03(5) pm, b = 659.41(5) pm, c = 680.24(5) pm, and β = 104.640(2)°) and is homeotypic with Ni₂In. The terbium ions adopt the indium sites and the sulfate and hydrogen sulfate anions are situated on the nickel sites. The compound shows green luminescence based on f-f-transitions and the positions of the f-d-excitation bands reveal a weak coordination behaviour of the sulfate anions. Tb(HSO₄)(SO₄) exhibits a second harmonic generation response comparable to KH₂PO₄ (KDP). Furthermore, the material is characterised by electrostatic calculations, infrared spectroscopy and thermal analysis.

RE2[B2(SO4)6] (RE = Y, La–Nd, Sm, Eu, Tb–Lu): a silicate-analogous host structure with weak coordination behaviour

The very first thorough investigation of the rare earth borosulfates RE₂[B₂(SO₄)₆] with RE = Y, La–Nd, Sm, Eu and Tb–Lu focusses on synthetic aspects and especially optical properties.

Ionic Transportation and Dielectric Properties of YF₃:Eu3+ Nanocrystals

The ionic transportation and dielectric properties of YF₃:Eu³⁺ nanocrystals are investigated by AC impedance spectroscopy. The ion diffusion coefficient and conductivity increase along with the doping concentration and reach their highest values at 4% of Eu³⁺. The difference of ionic radius between Eu³⁺ and Y³⁺ leads to the structural disorder and lattice strain, which deduces the increase of the ion diffusion coefficient and conductivity before 4% Eu³⁺ doping; then the interaction of the neighboring doping ions is dominated, which results in the difficulty of ion migration and decreases of the ion diffusion coefficient and conductivity. The strong dispersion of the permittivity in the low frequency region indicates that the charge carrier transport mechanism is the ion hopping in the system. The low-frequency hopping dispersion is affected by an interfacial polarization, which exhibits a Maxwell-Wagner relaxation process, and its loss peak shifts to higher frequency with the ionic conductivity increasing.

Hydrothermal synthesis, down-/enhanced up-converting, color tuning luminescence, energy transfer and paramagnetic properties of Ln3+ (Ln = Eu/Dy, Yb/Ho)-doped Ba2GdF7 multifunctional nanophosphors

Tunable multicolor, energy transfer processes, and paramagnetic properties of the Ba₂GdF₇:Ln³⁺ (Ln = Eu/Dy, and Yb/Ho) nanophosphors were studied.

Photoluminescence properties and energy transfer of Ce3+–Tb3+ co-doped SrAlF5 nanorods by a hydrothermal method

SrAlF₅:Ce³⁺,Tb³⁺ nanorods were synthesized via a mild hydrothermal process and the energy transfer from Ce³⁺ to Tb³⁺ was analyzed.

Luminescence Properties of SrZrO3/Tb(3+) Perovskite: Host-Dopant Energy-Transfer Dynamics and Local Structure of Tb(3+)

SrZrO3 perovskite (SZP) was synthesized using gel-combustion route and characterized systematically using X-ray diffraction and time-resolved photoluminescence techniques. A detailed analysis of the optical properties of Tb(3+) ions in SrZrO3 was performed to correlate them with the local environment of the lanthanide ions in this perovskite. Photoluminescence (PL) spectroscopy showed that emission spectrum consists of host as well as Tb(3+) emission indicating the absence of complete host-dopant energy transfer. On the basis of emission spectrum and PL decay study it was also observed that Tb(3+) is not homogeneously distributed in SrZrO3 perovskite; rather, it is occupying two different sites. It is corroborated using extended X-ray absorption fine structure studies that Tb(3+) is stabilized on both six-coordinated Zr(4+) and eight-coordinated Sr(2) site. The energies calculated using density functional theory (DFT) indicates that Tb occupation in Sr site is energetically more favorable than Zr site. The analysis of valence charge distribution also substantiated our structural stability analysis of site-selective Tb doping in SrZrO3. Time-resolved emission spectroscopy is employed to elucidate the difference in the spectral feature of Tb(3+) ion at Sr(2+) and Zr(4+) site. DFT-calculated density of states analysis showed that energy mismatch of Tb-d states with Zr-d and O-p states of SZP makes the energy transfer from host SZP to Tb(3+) ion difficult.

Investigation on YF3:Eu3+ architectures and their luminescence properties

The changeable matrix under different calcination temperatures leads to tunable luminescence properties.

Synthesis of rhombic hierarchical YF₃ nanocrystals and their use as upconversion photocatalysts after TiO₂ coating

A facile method has been developed to synthesize uniform nanoscale YF3 architectures. Interestingly, the unique YF3 nanostructure exhibits a flat and rhombic appearance which is formulated through the hierarchical assembly of YF3 nanocrystals along a specific crystalline orientation. Investigations on the formation process suggest that an assembly disassembly process is responsible for the construction of this novel structure. Enabled by doping with different lanthanides ions, the products can exhibit various down- or up-conversion luminescences, showing their potentials in serving as versatile host matrixes. The tunable luminescent properties allow designing effective upconversion photocatalysts when the doped YF3 nanostructures are coated with a TiO2 shell on their surface. In particular, the YF3@TiO2 hybrid structures have the porous nature that is partially inherited from the YF3 architectures, whose high surface-to-volume ratio facilitates their use as photocatalysts. In this article, we have demonstrated that the YF3:Yb,Tm@TiO2 structures exhibit satisfactory photocatalytic activities under the irradiation of both UV and near IR light. As compared with the conventional TiO2 catalysts, the hybrid structures here offer better performance in photocatalysis in the full solar spectrum. It is anticipated that this work provides a new approach to designing photocatalysts with responses to a broader spectral range.