Application of high-resolution magic-angle spinning NMR spectroscopy to define the cell uptake of MRI contrast agents

A new method, based on proton high-resolution magic-angle spinning ((1)H HR-MAS) NMR spectroscopy, has been employed to study the cell uptake of magnetic resonance imaging contrast agents (MRI-CAs). The method was tested on human red blood cells (HRBC) and white blood cells (HWBC) by using three gadolinium complexes, widely used in diagnostics, Gd-BOPTA, Gd-DTPA, and Gd-DOTA, and the analogous complexes obtained by replacing Gd(III) with Dy(III), Nd(III), and Tb(III) (i.e., complexes isostructural to the ones of gadolinium but acting as shift agents). The method is based on the evaluation of the magnetic effects, line broadening, or induced lanthanide shift (LIS) caused by these complexes on NMR signals of intra- and extracellular water. Since magnetic effects are directly linked to permeability, this method is direct. In all the tests, these magnetic effects were detected for the extracellular water signal only, providing a direct proof that these complexes are not able to cross the cell membrane. Line broadening effects (i.e., the use of gadolinium complexes) only allow qualitative evaluations. On the contrary, LIS effects can be measured with high precision and they can be related to the concentration of the paramagnetic species in the cellular compartments. This is possible because the HR-MAS technique provides the complete elimination of bulk magnetic susceptibility (BMS) shift and the differentiation of extra- and intracellular water signals. Thus with this method, the rapid quantification of the MRI-CA amount inside and outside the cells is actually feasible.     

Volume shrinkage dependence of ferromagnetic moment in lanthanide ferromagnets gadolinium, terbium, dysprosium, and holmium

The Gd-Ho series of lanthanide ferromagnets, which includes gadolinium (Gd), terbium (Tb), dysprosium (Dy), and holmium (Ho), undergoes similar structural transitions, e.g., the hcp→Sm-type→dhcp→fcc transitions, under pressure. Through high-field DC magnetic measurements and structural analyses, we found that the ferromagnetic moments disappeared at a specified critical pressure, which resulted in volume shrinkage of 16.7±1.7% for each ferromagnet. The results of the present study suggest that the disappearance of the ferromagnetic moments of Gd-Ho under pressure could be understood within the framework of a band picture related to volume shrinkage.     

稀土水杨酸配合物的光谱性质

合成了一系列稀土水杨酸配合物.分别研究了配合物的红外光谱(IR),紫外(UV)及荧光光谱(FS)性质.红外光谱研究表明,稀土和水杨酸主要通过羧基进行配位,而紫外光谱显示配合物中水杨酸和稀土离子之间的能量传递是主要过程;配合物的荧光性质研究发现水杨酸钆,水杨酸铽,水杨酸镝分子内能量传递效率高,具有很强的荧光性质.     

Magnetic and optical properties of nitroxide radicals and their lanthanide complexes

This paper reports the structural, magnetic and optical properties of three series of lanthanide complexes [Ln(radical)₄](ClO₄)₃, [Ln(radical)₂(NO₃)₃] and [Ln(radical)(hfac)₃] (Ln=Gd(III), La(III) or Eu(III)) with nitronyl or imino nitroxide radicals.The magnetic properties of the gadolinium complexes were studied. Along the series, most gadolinium(III) complexes exhibit antiferromagnetic Gd^III-radical interaction. These results are discussed.The full absorption and luminescence spectra of some lanthanide complexes and their uncoordinated free radical ligands were measured. The rich vibronic structure in luminescence and absorption spectra indicates that several excited states define the absorption spectra between 400 and 800 nm. Qualitative trends can be established between magnetic ground state properties and the energies and vibronic structure of the title compounds.     

Temperature and concentration dependences of thermal conductivity of solid solutions of gadolinium and dysprosium sulfides

Thermal conductivity of a number of solid solutions of gadolinium and dysprosium sulfides has been studied experimentally within the temperature range 80-400 K. The work offers the data on thermal conductivity coefficient and lattice thermal conductivity of the studied samples. It was found that replacement of gadolinium ions by dysprosium ions leads to significant decrease of the samples?? thermal conductivity and changes its temperature dependence character due to the resonance scattering of phonons by paramagnetic ions of dysprosium. Influence of this mechanism of phonon scattering conditions the area of anomalous change observed on the concentration dependence of thermal conductivity coefficient.     

分离稀土诱导位移的双稀土混合方法

稀土顺磁性诱导位移包含接触位移和偶极位移两种成份,如果把z>或D符号相反的两种稀土离子以适当的浓度比混合于同一溶液中。则实验上观测到的顺磁位移仅含一种成份,另外一种位移成份将被抵消。双稀土混合分离诱导位移技术要求底物分子与稀土离子间的的配位过程满足快速交换平衡条件且形成的稀土-底物配合物具有轴对称性或有效轴对称性。与其它分离诱导位移的方法相比,双稀土混合方法具有简单明确的特点。本文将这一方法应用于L-抗坏血酸¹³C稀土诱导位移的分离验证了其可行性。     

Short-range order changes induced by heat treatment in yttrium-aluminosilicate glasses

Short-range order and local atomic configuration in yttrium-aluminosilicate glasses doped with gadolinium were studied by infrared (IR) spectroscopy, ²⁷Al magic-angle-spinning nuclear magnetic resonance (MAS-NMR) and Gd³⁺ electron spin resonance (EPR) on as-prepared and heat-treated samples.A small amount of yttrium was replaced by gadolinium in the host glass because Y³⁺ and Gd³⁺ cations are quite similar and gadolinium ions can be used as structural sensor in electron paramagnetic resonance measurements. The results evidence weak changes in the structure of as-prepared glasses with respect to the coordination of aluminium atoms produced by gadolinium doping (0.2 and 0.5 mol%). New IR bands recorded from heat-treated samples are associated with stretching modes of hexacoordinated aluminium in AlO₆ octahedra. The effect of the heat treatment on aluminium environment is estimated by analysing the relative intensity of the component lines of simulated ²⁷Al MAS-NMR spectra. High-coordinated AlO_n species were identified in all samples. EPR results evidence the increase of the number of gadolinium sites with weak crystal field as effect of the structural relaxation.     

Isotope shifts and hyperfine structure of erbium,dysprosium, and gadolinium by atomic-beam diode-laser spectroscopy

A commercial diode laser system, without external frequency stabilization, has been used to study the isotope shifts and hyperfine structure in a near infrared transition of erbium, dysprosium and gadolinium. Specific mass shifts and relative values for the change in the radial nuclear charge parameters of the isotopes were obtained for erbium and dysprosium that compare well with literature values. The hyperfine structure constants measured for erbium fell within the range predicted from the results of other workers. The isotope shifts in the gadolinium transition investigated were too small for the spectrum to be resolved.     

Spectroscopic Study on the Photophysical Properties of Lanthanide Complexes with 2, 2′-Bipyridine-N, N′-dioxide

Five novel lanthanide (Eu3+, Tb3+, Gd3+, Sm3+ and Dy3+) complexes with 2, 2'-bipyridine-N, N'-dioxide (bipyO2) were synthesized and characterized by elemental analysis, IR spectrum. The triplet state energy of bipy O2 was determined to be 22275 cm(-1) with the phosphorescence spectrum of bipy O2 and its gadolinium complex. The photophysical properties of these complexes indicated that the triplet state energy of the ligand is suitable for the sensitization of the luminescence of Eu3+, Tb3+, Sm3+ and Dy3+, especially of Tb3+.     

Strongly dipolar Bose-Einstein condensate of dysprosium

We report the Bose-Einstein condensation (BEC) of the most magnetic element, dysprosium. The Dy BEC is the first for an open f-shell lanthanide (rare-earth) element and is produced via forced evaporation in a crossed optical dipole trap loaded by an unusual, blue-detuned and spin-polarized narrowline magneto-optical trap. Nearly pure condensates of 1.5 × 10(4) (164)Dy atoms form below T = 30 nK. We observe that stable BEC formation depends on the relative angle of a small polarizing magnetic field to the axis of the oblate trap, a property of trapped condensates only expected in the strongly dipolar regime. This regime was heretofore only attainable in Cr BECs via a Feshbach resonance accessed at a high-magnetic field.     

Detection of multiple elements in coal samples from Bangladesh by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) was used to analyze the coal samples from the Barapukuria coal mine of Bangladesh and coal from eastern India. Besides the major elements carbon and silicon, a number of minor and trace elements, such as iron, titanium, aluminum, calcium, sodium, copper, zirconium, neodymium, ytterbium, cerium, samarium, dysprosium and gadolinium were identified. In earlier work some researchers identified the lines around 279 and 280 nm as due to Mg II rather than Yb III. The reasons for identifying these two lines as due to ytterbium in the present work are explained. The detection of multiple elements in one experiment in a commonly used fuel demonstrated the versatility and multi-elemental capability of LIBS.     

二氧六环参与配位的稀土配合物的制备和荧光性能研究

利用二氧六环(dioxane)小分子作为第二配体,吡哌酸(PPA)作为第一配体合成了稀土荧光配合物Eu(PPA)3dioxane和Tb(PPA)sdioxane.这种小分子直接参与配位形成稀土配合物的现象很少见到.所合成的配合物通过与单独使用吡哌酸作为配体的配合物Eu(PPA)3和Tb(PPA)3对比,发现二氧六环对稀土配合物的荧光具有明显的增强效果,尤其是对Tb3+所形成的稀土配合物,荧光增强非常显著.二氧六环的参与配位,代替了原来的水分子,这样就会在一定程度上减少了热振动所造成的能壁损失,从而增强荧光.所制备的稀土配合物通过红外光谱、荧光光谱、荧光寿命等方法进行了表征.对于由Eu和Tb所形成的配合物,加入第二配体二氧六环对其荧光寿命的影响差别很大,这说明对于Eu和Tb所形成的配合物存在着不同的能鸶传递过程.这种荧光增强现象为检测小分子二氧六环的存在及其含量提供了一种新的方法.     

Antiferromagnetic photogalvanic effect in orthoaluminates

The antiferromagnetic photogalvanic effect in gadolinium, dysprosium, and terbium orthoaluminates is described within the phenomenological approach. The cases of linear and circular polarization of light are considered.     

含铕配合物荧光纳米纤维的制备及光学性质的研究

通过静电纺丝技术,将发光良好的稀土配合物Eu(DBM)₃·H₂O和Eu(DBM)₄·CPC纳米微粒复合到水溶性的聚乙烯基吡咯烷酮中,制备了具有稀土铕离子红色特性荧光的聚合物纳米纤维。通过对稀土配合物以及聚合物纳米纤维样品扫描电镜和透射电镜的测试,发现当稀土配合物复合到聚合物纳米纤维中后,由于与聚乙烯基吡咯烷酮乙醇溶解性良好,其微观结构发生了变化,得到了50～100 nm左右的比较均匀的线状结构。同时,通过对稀土配合物以及聚合物纳米纤维样品的荧光激发、发射光谱及荧光寿命进行研究,表明稀土配合物在聚合物纳米纤维中比其在粉末状有更高的发光强度及更长的荧光寿命,其原因在于高分子纳米纤维为稀土配合物提供了较稳定的化学环境。     

Determination of Dy(III) in the presence of Tb(III) using time-resolved luminescence

We have measured the relative luminescence quantum yields and luminescence lifetimes of Tb(III) and Dy(III) ions in complexes with pyrazole-5-carboxylic acids. Based on study of the time-resolved luminescence spectra of Tb(III) and Dy(III) complexes with 3-(6-benzodioxanyl)pyrazole-5-carboxylic acid, we have demonstrated the possibility in principle of determining Dy(III) in the presence of Tb(III) by separating the short-lived component of the luminescence of dysprosium, despite the practically complete overlap of the analytical bands of dysprosium by the terbium bands. This method was used to determine Dy(III) in luminescent materials: scandium borates doped with terbium and dysprosium. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 3, pp. 327–331, May–June, 2007.     

稀土配合物掺杂凝胶的原位光声光谱研究及其共发光效应

采用溶胶-凝胶方法,制备了Ln(Sal)₃·H₂O(Ln3+∶La3+, Nd3+, Tb3+; Sal: 水杨酸) 稀土配合物掺杂的二氧化硅凝胶样品。首次采用光声光谱对稀土配合物在凝胶中的形成进行研究。结果表明,经110 ℃热处理后,Tb3+, La3+和Nd3+配合物掺杂的凝胶样品在配体吸收处的光声强度依次明显增强;而对仅在室温陈化、干燥的湿凝胶样品,其配体吸收处的光声强度几乎完全相同。研究发现,未经适当的热处理过程凝胶样品中稀土配合物尚不能形成。结合荧光光谱,分析了凝胶中稀土离子配位环境的变化和稀土配合物的形成。首次发现了稀土芳香羧酸配合物掺杂凝胶的共发光效应,考察Tb_0.8Gd_0.2(Sal)₃·H₂O和Tb_0.8Nd_0.2(Sal)₃·H₂O配合物掺杂的凝胶样品,发现Gd3+离子的引入了增强了凝胶样品中Tb3+的发光效率,而Nd3+离子的引入明显减弱了凝胶中Tb3+的发光,并对共发光效应可能的机理进行了讨论。     

Micro-Meter Size Organogelator with Tri-Color Luminescence (Blue, Green and Red) Activated by Dy3+, Tb3+ and Eu3+ ions

The preparation of a novel type of low-molecular-weight amphiphilic organogelator bearing three long 14-alkyl chains and hydrophilic oligo(oxyethylene) groups was described. Ultra-violet absorption and fluorescence spectra give evidence of the energy transfer between organic ligands to lanthanide ions. Characteristic green, blue and red luminescence of the organogels were obtained and interesting emission properties of terbium, dysprosium and europium ions were unexpectedly observed at the first time during the order-disorder phase transition point (29 °C).     

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.     

Effects of film growth conditions on many-body photoemission satellites in heavy rare earths

Using angle-resolved synchrotron-radiation photoemission, we have studied the many-body satellite spectra of gadolinium and dysprosium overlayers on several substrates, including Cu(100), Ni(111), Si(111) and W(110). In addition to a 6 eV valence band satellite previous reported, we report the observation of a constant-kinetic-energy (CKE) satellite. We propose a model that describes both the 6 eV satellite as well as the newly observed CKE satellite. Our model explains in a single picture the presence and absence of the 6 eV satellite for a variety of film growth conditions.