Crystal field parameters in USiO4 from temperature dependence of paramagnetic susceptibility

Based on the experimentally determined temperature dependence of the paramagnetic susceptibility of tetragonal USiO₄ within the temperature range 2–500°K, the crystal field parameters of D_2d symmetry have been estimated (in cm^?1): B⁰₂ = ?24, B⁰₄ = ?1.25, B⁴₄ = ?12.8, B⁰₆ = ?0.031, B⁴₆ = 0.51, and $\text{B}{}^4{}_4\text{B}{}^4{}_6\text{≈ ?25}$. The Γ₅ doublet with the approximate composition: 0.78|±1> + 0.63|?3> is the ground level of the U⁴⁺ ion. Singlet Γ₁ lying ca. 100 cm^?1 above is the first excited level. The total splitting of the ³H₄ term of the U⁴⁺ ion was estimated to be equal to ca. 7500 cm^?1.     

Synthesis, Y and V-NMR of Er-doped zircon-type YVO4 and LUVO4

Y_0.99Er_0.01VO₄ and Lu_0.99Er_0.01VO₄ zircon-type compounds have been synthesized by solid-state reaction starting from the parent oxides. The obtained materials are single phase, well crystallized and homogeneous in the chemical composition.The magic angle spinning-NMR characterization points toward the substitutional nature of erbium on the rare earth site. The isotropic chemical shift of ⁸⁹Y in an orthovanadate is reported for the first time.     

Synthesis and luminescence properties of nanocrystalline YVO4:Eu

Nanocrystalline YVO₄:Eu³⁺ was synthesized by direct precipitation reaction, which was then annealed at different temperatures. The results of XRD showed that nanocrystalline YVO₄:Eu³⁺ could be obtained in solution at 60 °C, and the mean particle sizes of samples are increased as annealing temperature is increased. The results of TEM exhibit that the sizes of samples are around 5-30 nm. Studies on the excitation spectra show that there are a large number of the structural distortions in smaller particles. By analyzing line splitting patterns and peaks broadening in the emission spectra, we consider that the deviations in intensity patterns of ⁵D₀-⁷F₂ are affected by distortions of crystal lattice. Some abnormal behaviors can be attributed to higher ratio of surface to volume, which lead to the different local symmetry environment of Eu³⁺ ions on the surface.     

Synthesis and luminescence properties of Yb and Er doped KLa(WO4)2 nanoparticles

The luminescent nanocrystalline Yb³⁺ and Er³⁺ codoped KLa(WO₄)₂ has been prepared by Pechini method. X-ray diffraction and transmission electron microscope were used to study the structure of the obtained samples. The average grain size of these samples depended on the annealing temperature, increasing with the increase of the temperature. The cell parameters and the crystallite size of KYb_xEr_0.02La_0.98−x(WO₄)₂ nanocrystalline decreased with the increase of x value. Luminescence studies showed that the intensity of upconversion emission of the Yb³⁺ and Er³⁺ codoped samples was much stronger than that of the Er³⁺ single doped samples (pumped by 980 nm LD). The upconversion emission mechanisms suggested that all the three bands of upconversion emissions were two-photon process.     

Electron paramagnetic resonance study of vanadyl doped in zinc maleate tetrahydrate single crystals

Spectroscopy of vanadyl doped zinc meleate tetrahydrate single crystals has been studied by EPR in the X-band frequencies (∼9.5 GHz) and optical spectra. It is found that vanadium enters the zinc host lattice substitutionally.     

Tetragonal paramagnetic complex in Gd3+ doped Nd2(SO4)3·(NH4)2SO4·8H2O au]V.M. Malhotra

EPR studies of Gd³⁺ doped in single crystals of Nd₂(SO₄)₃·(NH₄)₂SO₄·8H₂O (hereafter referred to as NASO) at room (RT) and liquid nitrogen (LNT) temperatures exhibit that (1) the metal aquo complex has a tetragonal symmetry with abnormally low magnitudes of crystalline field parameters at RT and (2) NASO undergoes a possible phase transition between RT and LNT.     

CTAB-assisted hydrothermal synthesis of YVO4:Eu powders in a wide pH range

Rhombus-, rod-, soya bean- and aggregated soya bean-like YVO₄:Eu³⁺ micro- and nanostructures were synthesized by a cetyltrimethylammonium bromide (CTAB)-assisted hydrothermal method at 180 °C for 24 h in a wide pH range. The as-synthesized powders were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence spectroscopy (PL). The XRD results confirmed the formation of phase-pure YVO₄:Eu³⁺ powders with tetragonal structure under hydrothermal process in a wide pH range. Electron microscopic observations evidenced the morphological transformation of YVO₄:Eu³⁺ powders from rhombus-like microstructure to rod-, soya bean, and aggregated soya bean-like nanostructures with an increase in the pH of the synthesis solution. The results from the PL measurements revealed that the intensities of PL emission peaks were significantly affected by the morphologies and crystallinity of samples due to the absence of an inversion symmetry at the Eu³⁺ lattice site, and the highest luminescence intensity was observed for rod-like YVO₄:Eu³⁺ powders.     

Low temperature synthesis of nanocrystalline YVO4:Eu via polyacrylamide gel method

Nanocrystalline europium doped yttrium orthovanadate (YVO₄:Eu) were synthesized by the polyacrylamide gel method. For a comparative evaluation, bulk YVO₄:Eu was prepared by solid-state reaction. On the basis of X-ray powder diffraction, scanning and transmission electron microscopy and luminescence measurements, the polyacrylamide gel method appears to be a more efficient method to prepare the luminescence materials YVO₄:Eu with high homogeneity, purity and luminescence intensity.     

The resonance raman effects of VCl4 and SnI4

Raman spectra of VCl₄ and SnI₄ in solution are obtained using the exciting lines of a HeNe and an Ar⁺ laser. The spectra show a pre-resonance Raman effect with an enhancement of the stretching vibrations for shorter wavelengths of excitation. The features of the intensity variation are discussed quantitatively in terms of the frequency factors given by Albrecht and Hutley.     

The resonance raman effect of TiBr4 and TiL4

Raman spectra of TiBr₄ and Til₄ in solutions were obtained using the excitation lines of a HeNe and Ar⁺ laser. The spectra of TiBr₄ showed a pre-resonance effect with selective enhancement of the stretching vibrations for the shorter wavelength of excitation. A typical resonance Raman effect was observed for TiI₄ by the 5145 and 4880 Å excitation lines, which lie close to the maximum of the first absorption band, giving an intense overtone progression of the totally symmetric mode ν₁.     

Electron paramagnetic resonance study of doped synthetic crystals of struvite and its zinc analogue

The electron paramagnetic resonance (EPR) technique has been used to study the Mn²⁺ paramagnetic impurity complexes in synthetic struvite (MgNH₄PO₄β6H₂O) and the zinc isomorph (ZnNH₄PO₄β6H₂O). EPR of VO²⁺ ion complexes in vanadyl doped crystals of the zinc isomorph of struvite has also been studied. Two differently oriented, but otherwise identical complexes of both Mn²⁺ ion and VO²⁺ ion are found in these crystals. The spin Hamiltonian parameters indicate a large orthorhombic distortion of the [Mn²⁺(H₂O)₆] octahedra and an axial symmetry of the vanadyl complexes. The results indicate that in both manganese and vanadyl complexes, the metal ions have covalent bonding with the ligands.     

Rotational and hyperfine parameters of NH2(X2B1) from LMR spectra

Seventeen rotational transitions up to N=7 of the NH₂ radical in its ground vibronic state have been measured by far infrared laser magnetic resonance spectroscopy. Analysis of the Zeeman patterns and hyperfine structure yields precise rotational, spin-rotational and distortion parameters, and isotropic and anisotropic hyperfine interaction parameters for both ¹⁴N and ¹H nuclei.     

Bioconjugation of functionalized fluorescent YVO4:Eu nanocrystals with BSA for immunoassay

Novel fluorescent YVO₄:Eu nanocrystals were ∼15 nm in diameter and had been functionalized with phosphorous polyacrylic acids at the surface during the synthesis, which illuminated their potential in bioassays. In this paper, bovine serum albumin (BSA) was covalently coupled to activated nanocrystals from primary amine groups by EDC and sulfo-NHS chemistry successfully. Reaction condition, including concentration, pH value and separation methods, were carefully chosen and well discussed. Binding site number was determined simply by measuring BSA concentration using optimized microplate bicinchonic acid (BCA) assay and nanocrystals concentration according to their fluorescence emission in the monodisperse bioconjugate suspension. Transmission electron microscopy (TEM) imaging showed the monodispersity of the bioconjugates. Fluorescent characteristics were also retained. Immunoblots verified that BSA was covalently coupled to nanocrystals and remained immunoreactive. Finally, the two-step heterogeneous time-resolved fluoroimmunoassay (TR-FIA) of rabbit anti-BSA polyclonal antibody (PcAb) was operated to further validate the bioconjugates.