129Xe NMR study of Xe adsorption on multiwall carbon nanotubes

¹²⁹Xe NMR spectroscopy has been used to study the adsorption of Xe on multi-wall carbon nanotubes (MWCNT). The results obtained have shown the ¹²⁹Xe NMR ability to probe the intercrystalline (aggregate) and the inner porosity of CNT. In particular, the effects on porosity of tubes openings by hydrogen exposure and of ball milling were examined. Dramatic changes observed in the ¹²⁹Xe NMR spectra after moderate ball milling of MWCNTs were attributed to the destruction of the initial intercrystalline pore structure and to the Xe access inside the nanotubes. To examine the exchange dynamics the mixture of as-made and milled MWCNTs was studied with one- and two-dimensional (1D and 2D) ¹²⁹Xe NMR. The exchange between the interior of milled nanotubes and the aggregate pores of as-made MWCNTs was fast on the NMR acquisition time scale. The Xenon exchange between the interior of the as-made MWCNTs and the large aggregate pores occurred on a longer time scale of 10 ms, as was established by 2D ¹²⁹Xe NMR exchange spectroscopy. Variable temperature ¹²⁹Xe NMR data were also discussed and analyzed in terms of the fast exchange approximation.     

129Xe NMR研究MCM-22分子筛中的Xe-Xe作用

¹²⁹Xe NMR 测量得到Xe-Xe碰撞产生的δ_Xe-Xe，该值要比自由 的Xe和在NaY、CaA分 子筛中的值小很多. 通过一定的理论分析，证明在MCM-22分子筛超笼中的Xe-Xe碰撞作用类似于一维气体碰撞，同时表明δ_Xe-Xe也和δ_S（由Xe与孔壁碰撞产生 的化学位移）一样与分子筛的孔道结构密切相关.      

超极化129Xe磁共振分子影像学

磁共振分子影像学发展的主要瓶颈之一在于灵敏度的限制,基于激光光泵和自旋交换技术能获得增强4~5个量级的超极化¹²⁹Xe磁共振信号,因此超极化¹²⁹Xe磁共振分子影像学相对于传统MRI在灵敏度上表现出巨大的优势. 围绕提高灵敏度这一核心MRI问题及其在科学研究中的应用,该文介绍了目前基于超极化¹²⁹Xe的生物分子探针的基本结构和原理,阐述了与之相关的分子影像学方法和技术,同时评述了当前的最新研究进展和发展方向.     

激光极化129Xe的生物磁共振成像研究进展

激光光抽运自旋交换方法能够极大地增强＾１２９Ｘｅ核自旋极化,其获得的非平衡极化度远远高于在相同磁场里玻尔兹曼平衡值。     

超极化129Xe自动收集-升华装置研究

因其较高的核自旋极化度所提供的探测灵敏度,超极化¹²⁹Xe气体已被成功应用于动物和人体磁共振成像（MRI）.但是,在超极化¹²⁹Xe的收集-升华过程中,多种因素会导致¹²⁹Xe核自旋弛豫,进而限制其应用范围.本文通过理论模型分析和实验测量,验证了温度、磁场、螺旋冷阱材质等对冷冻恢复过程中超极化¹²⁹Xe弛豫的影响;同时,测量了自动收集-升华装置的稳定性.研究结果表明,升华方式和冷阱材质对¹²⁹Xe极化度损耗的影响显著;自制收集-升华装置的自动化程度高、长时间稳定,¹²⁹Xe极化度的恢复率可达到85.6% ± 4.7%.本研究非常有助于提升超极化¹²⁹Xe在动物和人体MRI中的使用效率.     

An apparatus for NMR of laser polarized 129Xe on single crystal surfaces

Due to a lack of at least 2 orders of magnitude in the amount of sample nuclei, single crystal surfaces are out of reach for conventional NMR measurements. Our aim is to prove that highly polarized ¹²⁹Xe provides a technique to overcome this restriction. Therefore an apparatus for polarizing ¹²⁹Xe up to 0.7 by spin transfer from optically pumped Rb has been designed as well as an NMR spectrometer in combination with a UHV chamber with sample cleaning, cooling and characterization abilities and a special manifold of glass stopcocks with a liquid nitrogen cooled trap for dosing nitrogen free polarized Xe into the chamber onto the surface. This revised version was published online in August 2006 with corrections to the Cover Date.     

超极化129Xe磁共振波谱和成像及在生物医学中的应用

文章简要介绍了磁共振波谱和成像的基本原理和对限制其灵敏度的挑战,详细阐述了为增强磁共振信号而制备超极化129Xe的物理机制,论述了129Xe在生物组织中的溶解性以及化学位移的特异性,综述了当前超极化129Xe在肺部、脑部成像领域的研究进展和在临床方面应用所取得的有代表性的研究成果,并讨论了基于超极化129Xe分子生物探针的超灵敏磁共振技术的研究前景,最后对超极化129Xe在生物医学领域的应用与发展作了展望.     

激光极化129Xe核自旋弛豫率的测量

由弱磁场下光泵自旋交换、强磁场中核磁共振测量方法,获得激光极化低压同位素¹²⁹Xe气体的核自旋弛豫率1/T₁及其与N₂气压力、环境温度的关系.结果表明:在291K的室温下,对于0~11 333.05Pa的N₂气压力范围,1/T₁随着N₂气压力的增加而增大;N₂气压力为1 466.63Pa时,1/T₁随着样品温度从234K到292K增高而减小     

NMR Study of Laser polarized ~(129) Xe in Low Pressure Natural Xenon Gas

Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｂｙｔｈｅｍｅｔｈｏｄｏｆｌａｓｅｒｏｐｔｉｃａｌｐｕｍｐｉｎｇｓｐｉｎ ｅｘｃｈａｎｇｅ ,ｔｈｅＮＭＲｓｉｇｎａｌｆｒｏｍ 1 2 9Ｘｅｇａｓｃａｎｂｅｇｒｅａｔｌｙｅｎｈａｎｃｅｄ[1 ] .Ｔｈｅｏｂｓｅｒｖｅｄｒａｔｉｏｏｆｓｉｇｎａｌｔｏｎｏｉｓｅｉｓｂｅｔｔｅｒｔｈａｎ 10 0 .Ｔｈｅａｍｐｌｉｆｉｃａｔｉｏｎｆａｃｔｏｒｏｆｔｈｅｎｕｃｌｅａｒｓｐｉｎｐｏｌａｒｉｚａｔｉｏｎｏｆｌａｓｅｒ ｐｏｌａｒｉｚｅｄ 1 2 9Ｘｅｉｓ 10 4ｂｙｃｏｍｐａｒｉｓｏｎｗｉｔｈｔｈｅＢ…     

超极化~(129)Xe磁共振波谱和成像及在生物医学中的应用

文章简要介绍了磁共振波谱和成像的基本原理和对限制其灵敏度的挑战,详细阐述了为增强磁共振信号而制备超极化129Xe的物理机制,论述了129Xe在生物组织中的溶解性以及化学位移的特异性,综述了当前超极化129Xe在肺部、脑部成像领域的研究进展和在临床方面应用所取得的有代表性的研究成果,并讨论了基于超极化129Xe分子生物探针的超灵敏磁共振技术的研究前景,最后对超极化129Xe在生物医学领域的应用与发展作了展望.