岩石的核磁共振自旋密度微成像

岩，心是油气储层的基本单元，其内部结构和渗流性质反映了油藏的基本特征．岩。心的精细描述是油藏描述、储层动态监测及设计强化采油方案的重要基础．本文利用核磁共振（NMR）自旋密度做成像，快速无损地观测到两类基本储油岩石——砂岩和灰岩的内部结构，提供了岩石渗透性、孔隙性及灰岩沉积环境等重要信息．1实验方法以自旋回波单片NMR成像脉冲序列为基础，设。P平面内样品的目施密度为P（。，v）．演化期t。，在。方向梯度场G。作用下，各处横向磁化矢量获得的相移为式中，7为共振核（在成像中一般为质子）的旋磁比，g为坐标位置·…     

2,5-双取代烷基苯磺酸钠胶束微结构的1H NMR研究

利用核磁共振化学位移变化, 自旋-自旋弛豫和2D NOESY(two-dimensional nuclear Overhauser enhancement spectroscopy)研究了一系列新合成的双取代烷基苯磺酸盐的胶束化. 结果表明, 邻位取代的是正烷烃链, 间位取代的是支烷烃链. 而且, 邻位取代的烷烃链越长, 参与形成胶束疏水核表面层的亚甲基个数越多. 因此, 每个分子在饱和吸附的油水界面上的面积越大. 间位取代的分支链在胶束疏水核中堆积得没有邻位取代的正烷烃链紧密. 分支链越短, 堆积得越不紧密. 描述了胶束中分子的相对排列.     

辐射交联顺1,4-聚丁二烯的NMR研究

用１３Ｃ ＮＭＲ方法,测定了辐射交联顺１,４ 聚丁二烯在室温下的自旋 晶格弛豫时间（Ｔ１）,核Ｏｖｅｒｈａｕｓｅｒ因子（ＮＯＥ）,和１３Ｃ ＮＭＲ线宽．以及凝胶本体１Ｈ ＮＭＲ的Ｔ１和Ｔ２弛豫时间,结果表明,辐射交联顺１,４ 聚丁二烯体系中,随着凝胶含量的增加各碳核质子的Ｔ１值变化很小,而—ＣＨ２—核的ＮＯＥ因子明显降低和１３Ｃ ＮＭＲ线宽增宽．以及１Ｈ ＮＭＲ的Ｔ１和Ｔ２表现的双指数弛豫特性反映了交联体系中大分子链段长程运动受阻以及饱和交联叔碳核—ＣＨ对链段运动的影响．     

酞侧基聚芳醚酮的核磁共振研究(Ⅰ)──链结构及NMR谱的归属

用1D NMR方法研究酞侧基聚芳醚酮(PEK-C)链结构,用二维同核化学位移相关与二维异核化学位移相关实验方法对1D NMR谱峰进行归属,探讨了二维异核远程相关实验在缩聚高分子研究中的应用,为PEK-C修饰机理以及共混相容机理的研究提供重要信息。溶液NMR谱图数据表明,PEK-C具有较规整的链结构。     

用二维核磁共振氢谱分析吡唑酮二当量品红成色剂的结构

利用300MHz低温超导核磁共振波谱仪对所合成的二当量吡唑酮品红成色剂的结构进行了分析。测定了该成色剂的一维~1H NMR,二维HOM2DJ谱,同核COSY谱等。     

用23Na和27Al固体核磁共振研究Na+在γ-Al2O3上的吸附状态

The adsorption of Na~+ on γ-alumina surface at four coverages of Na_2CO_3 (5%, 10%, 15%, and 20% wt/wt) was characterized by solid-state ~(23)Na and ~(27)Al NMR spectroscopy. The experimental results suggest that two distinct adsorbed species are present on alumina surface: surface species and surface salts. At lower coverages of Na_2CO_3 (5% and 10%), a surface species is predominant, in which the Na~+ cations are associated with the oxygen atoms of γ-alumina. With increasing the loading level to 15%, a second adsorbed species begins to appear which is attributed to the surface salt, Na_2CO_3, deposited on the solid surface. Further adsorption of Na_2CO_3 leads to an increase in the amount of surface salt while the amount of surface species remains unchanged. ~1H-~(27)Al CP/MAS experiments give the evidence that some Na~+ cations in the form of surface species are coordinated with the Br~(‥)onsted acid sites of γ-alumina. This may be the main driving force that improves appreciably the catalytic efficiency of Na_2CO_3/γ-Al_2O_3 catalyst.     

新型包覆数目可控的(CdTe/ZnS)nSiO2微球制备及细胞成像

以水相中快速合成的高质量核壳型CdTe/ZnS量子点为核,通过两步Stber法首次制备了硅壳包覆CdTe/ZnS数目可控的量子点微球(CdTe/ZnS)nSiO2,并完成氨基功能化修饰。通过紫外-可见分光光谱、红外光谱、荧光分光光谱、透射电子显微镜、粒度分析等相关方法对产物进行表征。结果证实:该合成方法不仅简便省时,易于放大生产,而且制备的氨基化微球具有52.1%的高荧光量子产率、稳定性强、生物相容性好。进一步将其用于标记Raw 264.7小鼠单核巨噬细胞和MCF-7人乳腺癌细胞,通过特征性膜成像表现膜电荷的分布,显示其在膜电荷对细胞行为的影响研究方面具有广阔的前景。     

T1-T2双模式磁共振造影剂的设计及应用

核磁共振成像作为一种无侵入的早期诊断方式早已在临床上得到了非常广泛的应用,其成像方式分为弛豫加权和扩散加权,其中弛豫加权又分为T₁加权成像和T₂加权成像。为了增强MR图像对比度,可通过引入造影剂,根据其增强类型可以分为阳性的T₁造影剂和阴性的T₂造影剂。虽然两种造影剂各有其优点,但是也存在着一些不足,因此一种全新的T₁-T₂双模态造影剂应运而生。T₁-T₂双模态造影剂的优势就在于可以利用同一台仪器,实现MRI成像在时间和空间上的精确匹配。本文系统地总结了T₁-T₂双模态造影剂的设计思路和其化学合成方法,并对其生物医学应用作了介绍。     

基于竞争配位的Ca2+特异性响应1H/19F磁共振成像分子探针

合成了一种含~(19)F的Mn~(2+)配合物3,12-二(2-氧代-2-((2,2,2-三氟乙基)氨基)乙基)-6,9-二氧杂-3,12-二氮杂十四烷酸锰(Ⅱ)(Mn(Ⅱ)-L,1),可实现对Ca~(2+)特异响应的~1H/~(19)F磁共振成像分析。~(19)F核在近距离的顺磁性Mn~(2+)影响下产生了顺磁弛豫增强作用,使~(19)F的横向弛豫时间T_2急剧缩短而磁共振信号锐减。当有Ca~(2+)存在时,与配体L的竞争配位使得~(19)F远离Mn~(2+)离子,从而~(19)F磁共振信号得到恢复。同时,由于Mn~(2+)离子从配合态变为游离态,水配位数增加使得其对~1H的纵向弛豫时间T_1弛豫性能增加,从而~1H磁共振成像信号也增强。相关实验的结果证实了该配合物是一种能对Ca~(2+)特异性响应的~1H/~(19)F磁共振成像探针。     

基于微液节点采样的定量质谱成像技术在包装材料中光引发剂定位与检测中的应用

该文针对传统方法中光引发剂定量检测耗时长、无空间分辨信息的缺陷,开发了基于微液节点采样－质谱系统的光引发剂定量成像方法,并将其用于包装纸中光引发剂的检测。研究表明,采样探针直接与质谱连接的接口方式具有更高的检测灵敏度,最优萃取剂可在1 min内实现单点采样超过90%的回收率,使得分析物可直接通过外标法定量。将该方法应用于包装纸中光引发剂的成像分析并与传统定量检测方法进行比较。结果显示：建立的成像方法可检测到比传统方法种类更多的光引发剂,且与传统方法的定量结果基本一致。另外,成像方法提供了更多丰富的空间分布信息,这对于包装纸中光引发剂的筛查定位以及指导和改进光固化油墨的涂布配方或工艺具有重大意义。     

Deuterium Rotating Frame NMR Relaxation Measurements in the Solid State under Static Conditions for Quantification of Dynamics

The feasibility of static deuterium rotating frame NMR relaxation measurements for characterization of slow timescale motions in powder systems is demonstrated. Using a model compound dimethyl sulfone-d₆, we show that these measurements yield conformational exchange rates and activation energy values in accordance with results obtained with other techniques. Furthermore, we demonstrate that the full Liouvillian approach as opposed to the Redfield approximation is necessary to analyze the experimental data.     

Solid State NMR Study of Polystyrene Nanolatex Particles(I) ~(13)C Spin-Lattice Relaxation Time

A wide range of physical methods has been used for studying the sintering behavior of bulk polystyrene, which has been the subject of AFM imaging, DSC measurement, Dilatometer meadurement, Fourier IR, and solid state NMR studies to investigate the physicochemical change and its relation to the electronic and magnetic performance. In recent years, more attention was paid to the size effect on annealing temperature for the latex particles with the diameter of less than 100 nm, which present…     

Solvent Effects in the Homogeneous Catalytic Reduction of Propionaldehyde with Aluminium Isopropoxide Catalyst: New Insights from PFG NMR and NMR Relaxation Studies

Solvent effects in homogeneous catalysis are known to affect catalytic activity. Whilst these effects are often described using qualitative features, such as Kamlet-Taft parameters, experimental tools able to quantify and reveal in more depth such effects have remained unexplored. In this work, PFG NMR diffusion and T₁ relaxation measurements have been carried out to probe solvent effects in the homogeneous catalytic reduction of propionaldehyde to 1-propanol in the presence of aluminium isopropoxide catalyst. Using data on diffusion coefficients it was possible to estimate trends in aggregation of different solvents. The results show that solvents with a high hydrogen-bond accepting ability, such as ethers, tend to form larger aggregates, which slow down the molecular dynamics of aldehyde molecules, as also suggested by T₁ measurements, and preventing their access to the catalytic sites, which results in the observed decrease of catalytic activity. Conversely, weakly interacting solvents, such as alkanes, do not lead to the formation of such aggregates, hence allowing easy access of the aldehyde molecules to the catalytic sites, resulting in higher catalytic activity. The work reported here is a clear example on how combining traditional catalyst screening in homogeneous catalysis with NMR diffusion and relaxation time measurements can lead to new physico-chemical insights into such systems by providing data able to quantify aggregation phenomena and molecular dynamics.     

Synthesis and complete NMR spectral assignment of thiophene-substituted sulfinyl monomers

This paper describes the synthesis of thiophene-substituted sulfinyl monomers. It comprises a four-step reaction by which the thiophene unit is built in via Suzuki coupling. These monomers could be used as building blocks for the preparation of conducting polymers via a new concept: the sulfinyl precursor route i.e. via thiophene substituted poly(p-phenylenevinylene) precursors. Furthermore, the complete 1H and 13C NMR signal assignment is presented. In addition to being essential for the characterization of the polymers concerned, it offers useful input information for further improvement of chemical shift prediction software. Furthermore, the T1C relaxation decay times are demonstrated to have the potential of being a fast and robust criterion for the spectral assignment of analogous monomers.     

Determination of Binding Constants for Cyclodextrin Complexes with Alkanols by the 1H NMR Measurements of Longitudinal Relaxation Time Using Tetramethylammonium Chloride as an Internal Reference

The longitudinal relaxation times (T₁)of ¹H NMR signals for a variety of alkanols in D₂Omarkedly decreased with increasing concentrations (c)of - and -cyclodextrins (CD). Tetramethylammoniumchloride (TMA) used as an internal reference wasavailable for evaluating an effect of solutionviscosity on relaxation rates R(=1/T₁), since TMAshowed no appreciable interaction with CD. Changes inthe ratio of R for alkanol protons to R for TMAprotons with c were analyzed by the curve-fittingmethod to give K_a. These K_a values agreedwell with those obtained by the analysis of changesin , indicating that T₁ measurement is available forthe determination of K_a for CD complexes. 2D ROESYspectra provided definite information on the molecularstructures of CD complexes with alkanols.     

Interpretation of NMR Relaxation as a Tool for Characterising the Adsorption Strength of Liquids inside Porous Materials

Nuclear magnetic resonance (NMR) relaxation times are shown to provide a unique probe of adsorbate–adsorbent interactions in liquid‐saturated porous materials. A short theoretical analysis is presented, which shows that the ratio of the longitudinal to transverse relaxation times (T₁/T₂) is related to an adsorbate–adsorbent interaction energy, and we introduce a quantitative metric e_surf (based on the relaxation time ratio) characterising the strength of this surface interaction. We then consider the interaction of water with a range of oxide surfaces (TiO₂ anatase, TiO₂ rutile, γ‐Al₂O₃, SiO₂, θ‐Al₂O₃ and ZrO₂) and show that e_surf correlates with the strongest adsorption sites present, as determined by temperature programmed desorption (TPD). Thus we demonstrate that NMR relaxation measurements have a direct physical interpretation in terms of the characterisation of activation energy of desorption from the surface. Further, for a series of chemically similar solid materials, in this case a range of oxide materials, for which at least two calibration values are obtainable by TPD, the e_surf parameter yields a direct estimate of the maximum activation energy of desorption from the surface. The results suggest that T₁/T₂ measurements may become a useful addition to the methods available to characterise liquid‐phase adsorption in porous materials. The particular motivation for this work is to characterise adsorbate–surface interactions in liquid‐phase catalysis.     

Water and oil signal assignment in low-moisture mozzarella as determined by time-domain NMR T2 relaxometry

A time-domain ¹H nuclear magnetic resonance relaxometry method was elaborated for the rapid microstructural characterization of mozzarella cheese. For this purpose, there is a strong need to know how the experimentally determined T₂ relaxation time distribution can be related to specific constituents in mozzarella. In this study, a detailed investigation is offered for fresh and aged low-moisture mozzarella cheese, often applied as a pizza cheese, by application of both a conventional Carr–Purcell–Meiboom–Gill (CPMG) sequence and a free-induction decay CPMG (FID-CPMG) sequence. The relaxation behavior was further elucidated by addition of deuterium oxide and by mild heat treatment of samples. The relaxation times of water protons in mozzarella were found to range from a few microseconds to some tens of milliseconds (in aged mozzarella) or to about hundred milliseconds (in fresh mozzarella). The upper limit of the T₂ distribution can even be extended to the seconds range upon releasing water protons from the mozzarella matrix using a mild heat treatment or upon addition of deuterated water. Both stimuli also provided evidence for the absorption of water into the cheese matrix. The potential release and uptake of water demonstrated that mozzarella acts as a very dynamic system during production and storage. The detected differences in the behavior of the water fraction between fresh and aged low-moisture mozzarella might be utilized to study the influence of either production and/or storage conditions on the cheese ripening process.