n型T'-214相超导体的结构和性质

T＇－214相化合物R2-xCexCuO4（R为稀土离子）成为超导体决定于R3+的离子半径大小、Ce4+的取代量和化合物的热处理时的稳定性．从Raman光谱实验结果提出热处理过程中发生电荷转移．Ce4+的取代引起TN（Cu）下降，当TN（Cu）降到0时，超导性出现。不同的稀土离子TN（Cu）不同，稀土离子的反铁磁性（AFM）与超导性（SC）共存。热电势的测量结果可以用双通道模型解释，n型超导体中电子与空穴共存．     

Coordination modes of 2-hydroxynicotinic acid in second- and third-row transition metal complexes

The new Pd(II), Pt(II), Re(V), Mo(VI) and W(VI) complexes of 2-hydroxynicotinic acid (H₂nicO), trans-[PdCl(HnicO)(PPh₃)₂]·0.75CH₃CN (1), K[PdCl(HnicO)₂]·H₂O (2), [Pd(HnicO)₂(bipy)] (3), cis-[PtCl(HnicO)(PPh₃)₂]·0.75CH₃OH·0.5H₂O (4), [PtCl(HnicO)(bipy)] (5), cis-[ReOI₂(HnicO)(PPh₃)] (6), Na₂[Mo₂O₆(HnicO)₂]·5H₂O (7), Na₂[Mo₄O₁₂(HnicO)₂]·2H₂O (8) and Na₂[W₂O₆(HnicO)₂]·5H₂O (9) have been prepared. The crystal structures of 1 and 4, were determined by X-ray diffraction and show the HnicO⁻ ligand coordinated to palladium or platinum through the nitrogen atom only. Infrared, Raman, ¹H and ¹³C{¹H} NMR spectroscopic data for the complexes are presented and are in agreement with the crystallographic results.     

Structure and vibrational spectra of the bis(betaine)-selenic acid molecular crystal

The crystal structure of bis(betaine)-selenic acid has been determined by X-ray diffraction as orthorhombic, space group Pbca, with a = 11.591(2), b = 22.930(5), c = 12.045(2) Å and Z = 8. The crystal comprises hydrogen selenate ions, HSeO⁻₄, and two distinct betaine molecules, which are held together into a complex by short hydrogen bonds. One of the betaine molecules is present as the zwitterion form (CH₃)₃N⁺---CH₂---COO⁻ and the second occurs as the protonated form (CH₃)₃N⁺---CH₂---COOH. Powder FTIR and Raman spectra were measured. An assignment of the observed bands to vibrations of the hydrogen bonds and internal vibrations of the hydrogen selenate ion and the betaine molecules is proposed.     

Broadband and band-selective IMPRESS-gHMBC: compensation of refocusing inefficiency with synchronized inversion sweep

Compensation of refocusing inefficiency in a gHMBC experiment by replacing the rectangular pi pulse with a pair of adiabatic pulses with synchronized inversion sweep (CRISIS) significantly improves the performance of the gHMBC experiment. The CRISIS-gHMBC experiment retains the pure absorptive shapes in F1 and hence results in better lineshape and higher resolution than the current versions of magnitude mode gHMBC spectra. When used as a broadband experiment, CRISIS-gHMBC, owing to better refocusing efficiency of the adiabatic pulse pairs, gives improved performance across the 13C spectral width. Moreover, it is shown that CRISIS-gHMBC is a robust and improved alternative and when used along with the IMPRESS (Improved Resolution using Symmetrically Shifted pulses) technique further increases the sensitivity and resolution without additional experimental time. The IMPRESS-CRISIS combination is demonstrated for broadband gHMBC and band-selective gHMBC experiments. The ICbs-gHMBC [IMPRESS-CRISIS-band-selective gHMBC] experiment is an attractive and better alternative to individual band-selective gHMBC.     

阴离子对水的羟基伸缩振动拉曼光谱的影响

通过比较纯水、NaX(X=F, Cl, Br, I)、Na2S、NaOH、NaNO3、Na2CO3、Na2SO4溶液的羟基伸缩振动拉曼光谱, 发现所研究的阴离子对水的结构都有破坏作用. 通过比较阴离子对水的羟基伸缩振动拉曼光谱的影响, 可将所研究的阴离子分为两类, 一类阴离子有F−、OH−、S2−、CO32−, 另一类阴离子有Cl−、Br−、I−、NO3−和SO42−. 它们的主要区别在于对羟基伸缩振动拉曼光谱3600 cm−1、2900−3100 cm−1处影响不同, 产生这些区别的原因在于阴离子与水分子之间氢键的强弱. 阴离子对水的羟基伸缩振动拉曼光谱的影响因素有离子半径、离子电荷和离子结构, 它们的影响程度为离子结构>离子电荷>离子半径.     

Coherent anti-Stokes Raman Scattering Microscopy.

Coherent anti-Stokes Raman scattering (CARS) microscopy is presented as a new nonlinear optical technique. The combination of vibrational spectroscopy and microscopy allows highly sensitive investigations of unlabelled samples. CARS is an ideal tool for studying a broad variety of samples. The main drawback of the technique is its non-zero-background nature, which implies that the signal has to be detected against a nonresonant background. The need to solve this problem is reflected in the rapid technological developments that have been observed during the last decade. Recent results show that CARS microscopy has the potential to become an important complementary technique that can be used with other well-established microscopic methods. Although it has some limitations, it offers unique access to many problems that cannot be tackled with conventional techniques. For this reason, it can be expected that the impressive growth of the field will continue.     

Orthogonal PbS nanowire arrays and networks and their Raman scattering behavior

Three-dimensional, orthogonal lead sulfide (PbS) nanowire arrays and networks have been prepared by using a simple, atmospheric pressure chemical vapor deposition (APCVD) method. These uniform nanowires (average diameter 30 nm) grow epitaxially from the surface of the initial PbS crystal seeds and form orthogonal arrays and networks in space. The growth mechanism has been explored, and the process was classified as homogeneous, epitaxial growth in the 200 directions. Furthermore, Raman spectra of PbS nanowires are reported here, and their characteristic Raman peak (190 cm(-1), no shoulder) could be used as a unique probe for the study of PbS nanomaterials.     

On the High Viscosity of Aqueous Solution of Lysozyme Induced by Some Organic Solvents

A remarkably high viscosity has been induced in protein aqueous solutions by the addition of certain structurally related organic solvents. The effect has been observed for lysozyme aqueous solutions containing tetramethylurea (TMU), dimethylsulfoxide (DMSO), dimethylformamide, and hexamethylphosphortriamide. The effect has also been induced in ferrocytochrome c aqueous solutions by TMU. Critical concentrations for both the protein and organic solvent were verified for the onset of the viscosity increase. A common feature of the solvents which were able to induce the effect is a dipolar moiety (C=O, S → O and P → O) and a nonpolar region represented by the methyl groups. The resulting fluids show an extremely restricted flow and a typical non-Newtonian, pseudoplastic behavior. Use was made of¹H nuclear magnetic resonance (NMR) and Raman spectroscopy to characterize protein structural modifications and of¹³C NMR to investigate changes in relaxation times and chemical shifts in the solvent/water solutions. A systematic rheological characterization of the systems was undertaken for some of the solvents, and unusual patterns of viscous effects were identified for the solvent/water systems both with and without protein. The process was found to be at least partially reversible, as concluded from the recovered original solution rheological characteristics and the original protein¹H NMR spectrum, after eliminating the organic solvent by ultrafiltration. The whole process was characterized as consisting of two mutually independent stages. The first involves an extensive conformational transition of the polypeptide backbone, from a predominantly α-helical to increased random coiled and β-sheet structures, with the occurrence of nonorthodox protein secondary structures at regions above the solvent critical point. The second stage consists of short-lived interchain contacts leading to an entanglement of the macromolecular system as a whole. A microphase reversion in the organic solvent/water mixture, supported by¹³C NMR and rheological results, is proposed as the driving force causing the observed behavior.     

Development of a universal Raman detector for microchromatography

Summary A detector for microchromatography in which Raman spectroscopy is used to identify the eluted species has been developed. The detector is designed to be applicable to a wide range of compounds without requiring the presence of a chromophore. Its use is illustrated in the analysis of nitro compounds on a 250 μm i.d. column. Raman spectra of each of the compounds could be identified as they passed the detector. The advatages of the use of fully deuterated solvents are demonstrated by the analysis of nitrobenzenes in methanol/water mobile phases. The detection limit for nitrobenzene using the Raman line at 1342 cm⁻¹ was 75ng.     

现场表面拉曼光谱研究Fe-Mo合金诱导共沉积

现场表面拉曼光谱结果显示，在0．2mol·L-1Na2MoO4,pH＝4．0的溶液中，电位正于0．5V（vsSCE）时只观察到多钼酸盐的拉曼峰（940、880和450cm-1）．负于-0．5V时，出现中心位于730cm-1的宽峰．同时电极表面有蓝色膜生成．表明混合氧化态（MO（Ⅳ），MO（Ⅴ））氧化膜的形成．730cm-1的峰在-1．9V时仍然存在，说明氧化膜没有被进一步还原．在钼酸钠溶液中同时含有0．1mol·L-1FeSO4和0．2mol·L-1柠檬酸时，中间态氧化膜的拉曼峰的中心移到740cm-1．且峰强度随着电位从-1．3V负移到-1．9V而逐渐减弱并最终消失．电极表面沉积层呈银白色，说明由于Fe2 的存在，钼的中间态氧化膜的结构发生了变化，能够被进一步还原形成Fe－Mo合金，表现出诱导共沉积的特征．