NMR Relaxivities of Paramagnetic Lanthanide-Containing Polyoxometalates

The current trend for ultra-high-field magnetic resonance imaging (MRI) technologies opens up new routes in clinical diagnostic imaging as well as in material imaging applications. MRI selectivity is further improved by using contrast agents (CAs), which enhance the image contrast and improve specificity by the paramagnetic relaxation enhancement (PRE) mechanism. Generally, the efficacy of a CA at a given magnetic field is measured by its longitudinal and transverse relaxivities r₁ and r₂, i.e., the longitudinal and transverse relaxation rates T₁⁻¹ and T₂⁻¹ normalized to CA concentration. However, even though basic NMR sensitivity and resolution become better in stronger fields, r₁ of classic CA generally decreases, which often causes a reduction of the image contrast. In this regard, there is a growing interest in the development of new contrast agents that would be suitable to work at higher magnetic fields. One of the strategies to increase imaging contrast at high magnetic field is to inspect other paramagnetic ions than the commonly used Gd(III)-based CAs. For lanthanides, the magnetic moment can be higher than that of the isotropic Gd(III) ion. In addition, the symmetry of electronic ground state influences the PRE properties of a compound apart from diverse correlation times. In this work, PRE of water ¹H has been investigated over a wide range of magnetic fields for aqueous solutions of the lanthanide containing polyoxometalates [Dy^III(H₂O)₄GeW₁₁O₃₉]^5– (Dy-W₁₁), [Er^III(H₂O)₃GeW₁₁O₃₉]^5– (Er-W₁₁) and [{Er^III(H₂O)(CH₃COO)(P₂W₁₇O₆₁)}₂]¹⁶⁻ (Er₂-W₃₄) over a wide range of frequencies from 20 MHz to 1.4 GHz. Their relaxivities r₁ and r₂ increase with increasing applied fields. These results indicate that the three chosen POM systems are potential candidates for contrast agents, especially at high magnetic fields.     

二（2,4,4—三甲基戊基）膦酸萃取Er（Ⅲ）的动力学

用新型恒界面池法首次研究了二（２，４，４－三甲基戊基）膦酸在盐酸介质中萃取Ｅｒ（Ⅲ）的动力学，测定了流体线性流速、有机相浓度、水相浓度和酸度、温度及界面面积等因素对萃取速率的影响，提出其速率方程，求出萃取反应的活化能，并对萃取反应机理进行了探讨．     

The optical properties of thin erbium films

The effective dielectric constant, ε′₂, of very thin films of erbium on sodium chloride substrates was determined from measurements of normal incidence reflectance and transmittance in the visible spectrum. ε′₂ showed a maximum which moved to longer wavelengths as the film thickness increased. Electron microscopy revealed that the film islands grew flatter and more irregular with thickness. The shape factor of the islands, F, was calculated by a modified Maxwell-Garnett method and became smaller as the film thickness increased.     

锁相环路对噪声的抑制性能与锁相放大技术

本文从锁相技术基本原理出发,运用统计观点对噪声和干扰抑制作用从六个方面加以定性和定量分析,从而突出锁相环路的窄带虑波特性,并介绍了 SR510-型锁相放大器具有高精度、高灵敏度、高抗扰度和高增益放大的性能.     

铒玻璃激光器研究

叙述磷酸盐铒玻璃激光器的偿试性实验研究及其静态和转镜调Ｑ特性。     

Beiträge zur Organolanthanidchemie. II. Cylopentadienyllanthanid-1,3-butadien-Komplexe – Darstellung,Eigenschaften und Reaktionen

Contributions to Organolanthanide Chemistry. II. Cyclopentadienyllanthanide 1,3-Butadiene Complexes – Synthesis, Properties, and Reactions From cyclopentadienyllanthanide dihalides and “magnesium butadiene” Cp*La(C₄H₆) · MgI₂ · 3 THF ( I ), Cp*Ce(C₄H₆) · MgBr₂ · 2 THF ( II ), Cp*Nd(C₄H₆) · MgCl₂ · 2 THF ( III ), (1,3-(t-C₄H₉)₂C₅H₃)Nd(C₄H₆) · MgCl₂ · 2 THF ( IV ), CpEr(C₄H₆) · MgCl₂ · 2 THF ( V ) and (1,3-(t-C₄H₉)₂C₅H₃)Lu(C₄H₆) · MgCl₂ · 2 THF ( VI ) were obtained as highly air sensitive complexes which react easily with proton active compounds and molecules with multible bonds. The reaction products with diphenylamine and carbon dioxide Cp*Nd(NPh₂)₂ · NHPh₂ ( VII ) and Cp*Ce(O₂CC₄H₆CO₂) ( VIII ) are discribed. I–VIII were characterized by elementary analysis, i.r., ¹H and ¹³C n.m.r., and EI-MS spectra.     

二氧化锆纳米材料中三价铒离子的上转换发光

固态蓝绿光源非常适合于高强度光存储、色平板、光电和医疗诊断，迄今为止，对各种晶体中上转换发光进行了广泛的研究。三价铒离子由于其相当高的上转换发光速率被作为一种激活离子而受到研究者的表睐。我们用共沉淀法制备了掺铒离子的二氧化锆纳米材料，并对纳米的结构，颗粒大小，声子能量进行了表征；用980nmLD和F－4500荧光分析仪测量了两种样品的上转换发射光谱，并观察到强的绿色发射和弱的红色发射，出现这种发射现象的原因是由于低的掺杂浓度和低的声子能量，通过发光强度和泵浦电流关系的实验。我们得到：蓝色和红色上转换发射分别来自三光子，双光子和双光子过程。     

Diffusion of Solvents and Cations in Porous Sol-Gel Glass

Diffusion coefficients for water, cyclohexane, toluene, chloroform, acetone and acetonitrile in porous sol-gel glass were determined using the diaphragm and radioactive tracer techniques. Polar solvents were found to diffuse faster than nonpolar solvent within porous sol-gel glass. The diffusion coefficients of Nd³⁺ and Er³⁺ inside porous sol-gel glass were determined from concentration profiles within monoliths impregnated by 1.6 M rare earth salts dissolved in either acetone or water. To study the effects of ligands on the diffusion, four different erbium salts were used: nitrate, chloride, bromide, and perchloride. It was found that the diffusion rate increases with decreasing radius of rare earth coordination sphere.     

微量铒对LF3铝合金铸态组织的影响

采用金相显微镜，扫描电镜和X射线衍射仪等手段分析研究了LF3铝合金中添加0．3％Er后的合金铸态及均匀化退火态的组织。结果表明：微量铒的加入可显著细化LF3铝合金的铸态组织，使其枝晶网胞尺寸明显减小，网胞间共晶化合物也更稀薄；同时，使第二相化合物更细小，分布也更均匀；微量铒的加入可形成Al3Er稀土化合物，没有发现粗大的块状化合物。其机制是由于生成了LI2型结构的，在晶体结构和点阵常数上都与Al基体（面心立方，a=0.405nm)相似的Al3Er稀土化合物，起到非均质形核核心的作用。     

HEH[EHP]从H2SO4介质中萃取Er（Ⅲ）的动力学和机理

本文采用充分混合法研究了HEH〔EHP〕-正庚烷从H_2SO_4介质中萃取Er(Ⅲ)的动力学,考察了水相酸度、硫酸根离子浓度和萃取剂浓度对萃取速率的影响,提出了萃取速率方程,并讨论了萃取机理。