Investigation of THz birefringence measurement and calculation in Al₂O₃ and LiNbO₃

Based on the polarization-sensitive terahertz time-domain spectroscopy, we measured the birefringence for Al?O? and LiNbO? single crystals, which correspond to trigonal structures that have an uniaxial birefringence, in the THz frequency range of 0.25 to 1.4 THz. For more comprehensive understanding of the THz birefringence, the measured birefringence is compared with the results of ab initio calculations. The measured birefringence shows good agreement with the calculated value.     

Effect of γ-radiation on optical properties of Eu2+ ions in the KCl: Eu2+ system

Emission spectra and luminescence time decay of Eu²⁺ ions in KCl crystals annealed at 873 K and quenched to room temperature before irradiation were measured at 80 K after -irradiation which was performed at 295 and 200 K. The results are consistent with radiation-induced aggregation of the original isolated europium dipoles.     

A facile synthesis, in vitro and in vivo MR studies of d-glucuronic acid-coated ultrasmall Ln₂O₃ (Ln = Eu, Gd, Dy, Ho, and Er) nanoparticles as a new potential MRI contrast agent

A facile one-pot synthesis of d-glucuronic acid-coated ultrasmall Ln(2)O(3) (Ln = Eu, Gd, Dy, Ho, and Er) nanoparticles is presented. Their water proton relaxivities were studied to address their possibility as a new potential MRI contrast agent. We focused on the d-glucuronic acid-coated ultrasmall Dy(2)O(3) nanoparticle because it showed the highest r(2) relaxivity among studied nanoparticles. Its performance as a T(2) MRI contrast agent was for the first time proved in vivo through its 3 T T(2) MR images of a mouse, showing that it can be further exploited for the rational design of a new T(2) MRI contrast agent at high MR fields.     

Ambient gamma radiation levels (indoor and outdoor) in the villages around Jaduguda (India) using card-based CaSO₄: Dy TL dosemeters

A systematic study of the gamma radiation levels (indoor and outdoor) in the villages surrounding the uranium-enriched regions around Jaduguda, India has been undertaken by monitoring selected dwellings in six villages. Each dwelling unit was monitored for a total duration of 1 y. The gamma radiation measurements were carried out using card-based CaSO(4): Dy thermoluminescent dosemeters. The estimated average annual gamma dose values for indoor and outdoor were 980 and 924 (μGy y(-1)), respectively, for the entire region studied. The maximum indoor and outdoor gamma doses experienced in North Dungridih and South Dungridih villages were 1305 and 1223 (μGy y(-1)), respectively. The minimum indoor and outdoor gamma dose values observed in Chatikocha village were 624 and 696 (μGy y(-1)), respectively. Seasonal variation of the indoor gamma values was not observed during the year; however, a small variation was seen with the type of building materials used for construction purposes. A statistical analysis was attempted to characterise the distribution of terrestrial gamma radiation obtained in the study area. The average quarterly indoor gamma values for spring, summer, monsoon and winter seasons as prevalent in the regions were 267±71, 262±54, 213±91, 238±66 (μGy 90 d(-1)), respectively. The annual effective doses to the local population residing in the selected dwelling units were estimated to be 0.6 and 0.1 (mSv y(-1)) for indoor and outdoor, respectively, using an occupancy factor of 0.8 and 0.2.     

Investigation of the iron doping on the structural,optical, and magnetic properties of Fe-doped ZnO nanoparticles synthesized by sol–gel method

Journal of Materials Science: Materials in Electronics - In this work, the compatibility of zinc oxide for spintronic applications motivated the development of single-phase Fe/ZnO nanostructures by...     

Synthesis,structural and optical studies of sol–gel Gd2O3:Eu3+, Tb3+ films

Eu³⁺ and Tb³⁺ co-doped Gd₂O₃ films were elaborated by sol–gel process and dip-coating technique. The films were synthesized by hydrolysis of gadolinium pentanedionate. A homogeneous and stable sol was obtained by the reaction with acetylacetone. Gd₂O₃:Eu³⁺, Tb³⁺ films were crystallized around 500 °C; at an increase of temperature up to 700 °C, oriented growth of (4 0 0) face was observed. The obtained transparent Gd₂O₃: 2.5 at.% Eu³+, 0.005 at.% Tb³⁺ waveguide films at 700 °C display significant optical properties. Different crystallographic properties can be obtained in Gd₂O₃:Eu³⁺, Tb³⁺ films with varying sintering temperatures.     

A study on the kinetics and mechanism of silver-cluster formation in zeolite Ag-X by diffuse reflectance spectroscopy

The kinetics of silver-cluster formation was investigated using diffuse reflectance spectroscopy (DRS), by following the intensity changes of the absorption band at 410 nm that appears under the thermal dehydration of zeolite Ag-X. Using the theoretical model of diffusion into a sphere, it was shown that the diffusion of Ag⁺ is the rate determining step in the silver-cluster formation. This model also enabled the calculation of some kinetic parameters.     

Coordination chemistry of Ca sites at the surface of nanosized hydroxyapatite: interaction with H₂O and CO

The affinity towards water of a selection of well-defined, nanostructured hydroxyapatite (HA) samples was investigated by H(2)O vapour adsorption microcalorimetry and infrared (IR) spectroscopy. A large hydrophilicity of all investigated materials was confirmed. The surface features of hydrated HA were investigated on the as-synthesized samples pre-treated in mild conditions at T=303 K, whereas dehydrated HA features were characterized on samples activated at T=573 K. The relatively large hydrophilicity of the hydrated surface (-Δ(ads)H~100-50 kJ mol(-1)) was due to the interaction of water with the highly polarized H(2)O molecules strongly coordinated to the surface Ca(2+) cations. At the dehydrated surface, exposing coordinatively unsaturated (cus) Ca(2+) cations, H(2)O was still molecularly adsorbed but more strongly (-Δ(ads)H~120-90 kJ mol(-1)). The use of CO adsorption to quantify the Lewis acidic strength of HA surface sites revealed only a moderate strength of cus Ca(2+) cations, as confirmed by both microcalorimetric and IR spectroscopic measurements and ab initio calculations. This result implies that the large HA/H(2)O interaction energy is due to the interplay between cus Ca(2+) sites and nearby hydrophilic PO(4) groups, not revealed by the CO probe. The lower density of cus Ca(2+) cations at the 573 K activated HA surface with respect to the pristine one did not affect the whole hydrophilicity of the surface, as the polarizing effect of Ca sites is so strong to extend up to the fourth hydrated layer, as confirmed by both high-coverage microcalorimetric and IR spectroscopic data. No specific effects due to the investigated specimen preparation method and/or different morphology were observed.     

Chiral discrimination in the gas phase using different transducers: thickness shear mode resonators and reflectometric interference spectroscopy

The discrimination of optical isomers (enantiomers) in the gas phase has been performed using two different analytical tools: thickness shear mode resonators (TSMRs) and reflectometric interference spectroscopy (RIFS). The selective coatings included both enantiomers ((S)- and (R)-receptor) of a Chirasil-Val derivative (stationary phase material in GC) with octyl side chains. Successful discrimination of the enantiomers of different types of analytes (amino acids and lactates) was achieved. The results of both transduction methods were consistent and in good agreement with GC measurements. In addition, different mixtures of both enantiomers of the respective analyte were measured, and the enantiomeric composition could be quantitatively determined with excellent reliability. Since the sensors allow on-line monitoring (not possible with GC) of enantiomeric purity, an application in industrial synthesis (process control) of such compounds represents an interesting feature, especially with regard to the tested derivatives of lactic acid.     

Analysis of organic compounds by particle beam/hollow cathode atomic emission spectroscopy: determinations of carbon and hydrogen in amino acids

A detailed evaluation of the analytical characteristics of a particle beam/hollow cathode glow discharge atomic emission spectroscopy (PB/HC-AES) system is described for applications in the area of organic sample analysis. The optimization of sample introduction, nebulization parameters, and glow discharge conditions was performed for the elemental analysis (focusing on C and H) of a group of amino acids. By use of a high-efficiency thermoconcentric nebulizer, analyte particles are introduced into a heated hollow cathode glow discharge source, in either flow injection or continuous-flow mode, for subsequent vaporization/atomization and excitation. Nebulization temperature, solvent composition, and liquid flow rate were studied to elucidate their roles in the ultimate analyte emission characteristics for organic compound analysis. The hollow cathode operating discharge current and gas pressure were optimized, with the general responses found to be similar to those for the case of metal analysis. Background interferences from solvent and additive media on carbon and hydrogen determinations were studied and substantially reduced. The analytical response curves for carbon and hydrogen present in amino acids were obtained using 200 μL injection volumes, showing less than 10% RSD for replicate injections over a concentration range of 10-250 ppm, with detection limits of 3 and 1 ppm, respectively, for C (I) and H (I) emission. Subsequent studies of the response of carbon and hydrogen emission signal intensities to differences in amino acid stoichiometries suggest a capability of the PB/HC-AES system for the determination of empirical formulas based on H (I)/C (I) intensity ratios.     

Adsorption of lead(II) on O₂-plasma-oxidized multiwalled carbon nanotubes: thermodynamics, kinetics, and desorption

O(2)-plasma-oxidized multiwalled carbon nanotubes (po-MWCNTs) have been used as an adsorbent for adsorption of lead(II) in water. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy measurements show that the bulk properties of MWCNTs were not changed after O(2)-plasma oxidation. The adsorption capacity of MWCNTs for lead(II) was greatly enhanced after plasma oxidation mainly because of the introduction of oxygen-containing functional groups onto the surface of MWCNTs. The removal of lead(II) by po-MWCNTs occurs rather quickly, and the adsorption kinetics can be well described by the pseudo-second-order model. The adsorption isotherm of lead(II) onto MWCNTs fits the Langmuir isotherm model. The adsorption of lead(II) onto MWCNTs is strongly dependent upon the pH values. X-ray photoelectron spectroscopy analysis shows that the adsorption mechanism is mainly due to the chemical interaction between lead(II) and the surface functional groups of po-MWCNTs. The thermodynamic parameters (ΔH°, ΔS°, and ΔG°) calculated from the adsorption isotherms suggest that the adsorption of lead(II) onto MWCNTs is endothermic and spontaneous. The regeneration performance shows that lead(II) can be easily regenerated from po-MWCNTs by altering the pH values of the solution.     

The Effect of the Flux B203 and the Role of Ion RE3＊ in CaAI204： Eu2＋, Nd3＋, RE3＋ Phosphor （RE： Dy, Gd, Tb）

The long afterglow phosphors CaA1204： Eu2＋, Nd3＋, RE3＋ （RE： Dy, Gd, Tb） were prepared by the combustion method at 580℃ for 5 min. In this method, the B203 oxide was used as flux. The influences of the flux B203 quantity and the role of ion RE3＋ （RE： Dy, Gd, Tb） in the phosphor CaAI204： Eu2＋, Nd3＋ were studied systemically. The X-ray diffraction pattern, scanning electron microscopy graphic, the photoluminescence spectra and decay time were presented. The emission spectra of phosphors had a broad band with maximum at 444 nm due to electron transition from the 4f65dI to the 4f7 of ion Eu2＋. It is showed that Nd3＋ and RE3＋ ions generated traps that resulted in the long persistent phosphorescence. Simultaneously, when the concentration of RE3＋ ion was high, they generated also emission centers in the phosphor.     

Luminescence properties and tunable emission of Ca3MgSi2O8:Eu3+, Bi3+ phosphor with Bi3+ → Eu3+ energy transfer

Journal of Materials Science: Materials in Electronics - In this work, Ca3MgSi2O8:Bi3+, Ca3MgSi2O8:xEu3+ (x?=?0, 2, 4, 6, 8, and 10 mol%), and Ca3MgSi2O8:6%Eu3+, yBi3+...     

Synthesis and Study of Uranates of Rare-Earth Elements of Compositions LnU3O10.5·6H2O (Ln = La,Ce, Pr,Nd, Sm), LnU6O19.5·10H2O (Ln = Nd,Sm, Eu,Gd, Tb,Dy), and LnU2O7.5 (Ln = Dy,Ho, Er,Tm, Yb,Lu)

Radiochemistry - The interaction of synthetic skupite UO3·2.25H2O with aqueous solutions of La, Ce, Pr, Nd, Sm, Eu,Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu nitrates under hydrothermal conditions at a...     

Tunable luminescence and energy transfer properties of Sr₃AlO₄F:RE³+ (RE = Tm/Tb, Eu, Ce) phosphors

Sr(3)AlO(4)F:RE(3+) (RE = Tm/Tb, Eu, Ce) phosphors were prepared by the conventional solid-state reaction. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), photoluminescence (PL) spectra, as well as lifetimes were utilized to characterize samples. Under the excitation of UV light, Sr(3)AlO(4)F:Tm(3+), Sr(3)AlO(4)F:Tb(3+), and Sr(3)AlO(4)F:Eu(3+) exhibit the characteristic emissions of Tm(3+) ((1)D(2)→(3)F(4), blue), Tb(3+) ((5)D(4)→(7)F(5), green), and Eu(3+) ((5)D(0)→(7)F(2), red), respectively. By adjusting the doping concentration of Eu(3+) ions in Sr(3)AlO(4)F:0.10Tm(3+), 0.10Tb(3+), zEu(3+), a white emission in a single composition was obtained under the excitation of 360 nm, in which an energy transfer from Tb(3+) to Eu(3+) was observed. For Sr(3)AlO(4)F:Ce(3+),Tb(3+) samples, the energy transfer from Ce(3+) to Tb(3+) is efficient and demonstrated to be a resonant type via a dipole-quadrupole interaction by comparing the experimental data and theoretical calculation. Furthermore, the critical distance of the Ce(3+) and Tb(3+) ions has also been calculated to be 9.05 ?. The corresponding luminescence and energy transfer mechanisms have been proposed in detail. These phosphors might be promising for use in near-UV LEDs.     

Dehydration/amine intercalation in Zn(O3PR)–H2O phosphonates: the missing link,X-ray structure of Zn(O3PCH3)

The hydrothermal synthesis of colorless crystals of Zn(O₃PCH₃) was achieved using a solution of zinc nitrate and methylphosphonic acid (1:1) in water, in the presence of thiourea. The structure was determined by single crystal X-ray diffraction [monoclinic, space group P2₁/c (No. 14), a=8.7226(9) Å, b=5.2156(7) Å, c=10.847(1) Å, V=389.48(9) ų, Z=2]. From this result, the mechanism of the structure modification taking place during the dehydration of Zn(O₃PR)–H₂O phosphonates was clearly demonstrated.     

Judd–Ofelt theory: optical absorption and NIR emission spectral studies of Nd3+:CdO–Bi2O3–B2O3 glasses for laser applications

This article reports on the optical absorption and NIR emission properties of Nd³⁺ ions doped CdO–Bi₂O₃–B₂O₃ (CdBiB) glasses. Judd–Ofelt theory has been applied to calculate the oscillatory strengths of the transitions in the absorption spectra and also the intensity parameters Ω_λ (λ = 2, 4, and 6). These results were then used to compute the radiative properties of emission transitions of Nd³⁺:CdBiB glasses. From the NIR emission spectra of Nd³⁺:CdBiB glasses, three NIR emission bands are observed at 900, 1069, and 1338 nm and assigned to the transitions (⁴F_3/2 → ⁴I_9/2), (⁴F_3/2 → ⁴I_11/2), and (⁴F_3/2 → ⁴I_13/2), respectively. The concentration quenching phenomenon has also been explained. The stimulated emission cross-section and FWHM values were calculated for all the Nd³⁺:CdBiB glasses.