Magnetic Properties of Iron Clusters in Silver

Time differential perturbed γ-γ angular correlation technique was used to measure the magnetic hyperfine field (MHF) at Tb sites in the intermetallic compound Tb₃In₅ using the ¹⁴⁰La → ¹⁴⁰Ce nuclear probe. The measurements were carried out in the temperature range of 8 to 295 K. Two different temperature dependent magnetic frequencies were observed below 30 K, which were assigned as ¹⁴⁰Ce substituting the two inequivalent Tb sites in the orthorhombic structure of Tb₃In₅. The temperature dependence of MHF also shows a possible deviation from an expected Brillouin-like behavior for temperatures below 18 K. A Néel transition at 27 K was observed from magnetization measurements in the samples. The magnetization as a function of the applied magnetic field was measured at two temperatures, 5 and 40 K, and the results show antiferromagnetic and a typical paramagnetic behavior, respectively. In both cases it was not observed saturation under high magnetic field.     

无机/有机稀土配合物杂化发光材料研究进展

近年来材料的发展趋势是功能互补,性能优化。稀土配合物发光强度大、单色性好,缺点是光稳定性和热稳定性较差,因此须将其掺入一定基质中,这样所得到的有机 /无机杂化发光材料,兼备了有机、无机材料的优点。根据杂化材料中稀土配合物与基质之间作用力不同,可分为第一类杂化材料(两相间以弱键如氢键等结合)和第二类杂化材料(两相间以强键如共价键等结合)。对这两类杂化材料近年来国内外的研究情况作了综合评述,并展望了其发展趋势。     

BaAl12O19:Mn2+和YPO4:Tb3+共混对等离子绿色发光体发光性能的改善

等离子体平板显示用绿色发光粉主要有硅酸盐(Zn2S iO4∶Mn2+)、铝酸盐(BaA l12O19∶Mn2+)、磷酸盐(YPO4∶Tb3+)和硼酸盐(YBO3∶Tb3+)4种体系。前两者具有量子效率高、色纯度好等优点,然而抗真空紫外辐照能力差,发光衰减时间长;Tb3+激活的磷酸盐和硼酸盐体系具有适宜的发光寿命,抗真空紫外辐射能力强,然而Tb3+的发射光是黄绿色,色纯度不够好,且发光亮度相对较弱。按一定的混合比率使BaA l12O19∶Mn2+和YPO4∶Tb3+均匀混合,组合这两种体系绿色发光粉各自的优点,优化了等离子体平板显示用绿色发光粉的整体性能。     

Synergistic effects on iodine release in potassium iodide solution by combination of ultrasound and visible light irradiations

Iodine release in potassium iodide solution has been investigated under the irradiations of ultrasound and visible light respectively and simultaneously. We have observed that the amount of iodine liberated under the combined irradiation of ultrasound and visible light is larger than the sum of that under the respective irradiations of ultrasound and visible light, indicating a synergistic effect of ultrasound and visible light irradiations. Based on the investigation of the reaction kinetics of iodine liberated, we have ascribed the synergistic effect to the perfect stirring of the photochemical reactor induced by the applying simultaneous ultrasound. The ideal stirring can result in the homogenization of the primary light effect in the whole reaction medium, which induces the acceleration of the photochemical reaction. On behavior of our knowledge, there are few reports on the investigations of utilizing the combination of ultrasonic energy and light energy to accelerate the reaction yield and rate as well as the kinetics of the reaction.     

Effect of varying lanthanide local coordination sphere on luminescence properties illustrated by selected inorganic and organic rare earth complexes synthesized in sol-gel host glasses

Inorganic and organic ligands were carefully selected to illustrate the effect of modifications in the local field environment around the rare earth lanthanide (III) on its emission properties. In this article two strategies were employed to enhance emission of lanthanides encapsulated in sol-gel glass. (i) Changing the symmetry around the lanthanide, which was diagnosed by changing the local environment around the lanthanide using different inorganic counter ions (acetate, nitrate and chloride) these ligands differ in their affinity toward the lanthanide first coordination sphere. The ligand that penetrates the lanthanide more results in more asymmetric environment and thus results in higher emission. The aim of this part was to demonstrate the change of symmetry on emission in the absence of energy transfer. Our results indicate that the acetate ion has the highest affinity toward the first coordination sphere followed by the nitrate while the chloride showed the lowest affinity. Penetration by the ligands ofthe lanthanide also results in removing OH quenchers surrounding the lanthanide and this further explains the boost in emission. (ii) A bulky organic ligand that forms a complex with the lanthanide is used. The organic ligand separates the lanthanide ion from inner O-H oscillators. In this case the chelating organic chromophore with suitable photophysical properties was employed to sensitize the lanthanide and thus energy transfer occurs via the antenna effect. The organic ligand absorbs UV light, then energy is transferred to the lanthanide and finally the lanthanide emits in the visible region. The first coordination environment surrounding europium was controlled by the ligand selection and the outer sphere was modified by doping the synthesized complexes in an optically transparent sol-gel glass host. The glass network carefully prepared by sol-gel process is effective in preventing free oxygen and water from attacking lanthanide -complexes without loss of luminescence. Emission spectroscopy measurements of the doped silica specimens confirmed the variation of Eu (III) emission depending on the first coordination sphere surrounding the europium ion. The encapsulation of the europium complexes was performed for two reasons: (i) to improve the stability of red phosphor with efficient and high color-purity characteristics under ultraviolet excitation and (ii) this work provides a framework for preparing transparent composite glasses that are robust hosts to study the fundamental interactions between nano-materials and light.     

Yb effect on the spectroscopic properties of Er-Yb codoped SnO2 thin films

We have investigated the optical properties of sol-gel thin films of tin dioxide (SnO₂) codoped with Er³⁺-Yb³⁺ as a function of Yb³⁺ concentration. The Judd-Ofelt model has been applied to absorption intensities of Er³⁺ (4f¹¹) transitions to establish the so-called Judd-Ofelt intensity parameters: Ω₂, Ω₄, Ω₆. Various spectroscopic parameters were obtained to evaluate their dependence and the potential of the samples as a laser material in the eye-safe laser wavelength (1.53 μm) as a function of Yb³⁺ concentration. An amelioration of the quality factor Ω₄/Ω₆ was found with Yb content. Both the IR photoluminescence (PL) intensity and the up-conversion emission, from Er³⁺ ion in SnO₂, were found to increase with Yb concentration. We show that the Yb³⁺ ion acts as sensitizer for Er³⁺ ion and contributes largely to the improvement of the spectroscopic properties of SnO₂:Er. The mechanism of up-conversion emission is discussed and a model is proposed. The results showed that sol-gel SnO₂ is promising gain media for developing the solid-state 1.5 μm optical amplifiers and tunable up-conversion lasers.     

Effect of the crystal potential on electronic polarizabilities of ions in alkaline earth chalcogenides

The electronic polarizabilities of ions in alkaline earth chalcogenides are estimated by taking account of the effect of the crystalline potential. The polarizabilities thus obtained are found to present a good agreement with experimental data. It has been shown that the polarizabilities and radii of alkaline earth and chalcogenide ions follow the polarizability-radius cube relation approximately well.     

抗坏血酸稀土对鱼类的急性毒性试验

本试验对抗坏血酸稀土对鱼类的急性毒性进行了研究。结果表明:抗坏血酸稀土对鲢鱼、草鱼、金鱼和泥鳅的96hrTLm值为50.14～495.27mg/l。根据鱼类急性毒性毒物的分级暂定标准,抗坏血酸稀土对鱼类属低毒物质。     

依文思蓝-溴酸钾催化体系测定亚硝酸根

本文研究了亚硝酸根的一个新指示反应。在稀磷酸溶液中,依文思蓝-溴酸钾的氧化还原反应受亚硝酸盐催化使依文思蓝褪色。测定灵敏度为7.8×10-11g/mL亚硝酸态氮[当lg（Ao/A）=0.001 b=l cm)。测定范围0—3.5μg NO2/25mL,相对标准偏差1.64%。已用于测定自来水和唾液中的NO2-。     

硅基稀土热扩散法初探

稀土元素在我国有丰富的贮量．近年来,稀土元素在各种新科技领域中得到不断的开发和利用．各类稀土功能材料在发光和光通信领域中正展现巨大的应用潜力［１］．稀土磁光薄膜材料是优良的记录介质;稀土Ｅｒ由于其特殊的电子结构,已用来制造掺铒光纤激光器和光纤放大器［２］;掺铒硅还可制造发光谱线单一的发光器件［３］,这为实现人们所期待的硅基光电集成提供了有益途径．此外,基于对掺铒硅荧光发射衰减时间的分析,可用于制造温度传感器［４］．因此,稀土在共价半导体材料如Ｓｉ、ＧａＡｓ中的行为研究日益受到重视．但这些工作主要…