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91.
Li1+2xTi2-xMgxP3O12固溶体系统结构31P NMR研究 总被引:1,自引:0,他引:1
本文应用固体高分辨31P NMR技术,以P原子作为结构探针,对以LiTi2P3O12为基质的Mg掺杂固溶体系统快离子导体的结构进行了研究。并利用P原子第二配位层阳离子场强与其化学位移的关系,确定了不同化学位移31P NMR谱线与固溶体结构中P原子局部结构单元Q°之间的关系,解释了Mg的掺入所引起的晶体结构的变化。 相似文献
92.
用~(13)C和~1HNMR波谱,探讨了聚环氧氯丙烷(PEPCH)的辐射效应,结果表明随着辐射剂量的增加,本体聚合物的~(13)CNMR谱中各基团的分辨率得以提高,~1HNMR谱中出现了裂解产物共振峰,T~1变短,表明PEPCH在限量空气氛中的辐射效应以大分子裂解反应为主,并通过特性粘度的测定,得到了证实。 相似文献
93.
Chaohui ZHANG 《数学年刊B辑(英文版)》2011,32(6):885-894
Let S be a Riemann surface that contains one puncture x. Let ℐ be the collection of simple closed geodesics on S, and let ℱ denote the set of mapping classes on S isotopic to the identity on S ∪ {x}. Denote by t
c
the positive Dehn twist about a curve c ∈ ℐ. In this paper, the author studies the products of forms (t
b
−m
∘ t
a
n
) ∘ f
k
, where a, b ∈ ℐ and f ∈ ℱ. It is easy to see that if a = b or a, b are boundary components of an x-punctured cylinder on S, then one may find an element f ∈ ℱ such that the sequence (t
b
−m
∘ t
n
a
) ∘ f
k
contains infinitely many powers of Dehn twists. The author shows that the converse statement remains true, that is, if the
sequence (t
b
−m
∘ t
a
n
) ∘ f
k
contains infinitely many powers of Dehn twists, then a, b must be the boundary components of an x-punctured cylinder on S and f is a power of the spin map t
b
−1 ∘ t
a
. 相似文献
94.
Chaohui Zhou Hui Wu Chusen Huang Mingliang Wang Nengqin Jia 《Particle & Particle Systems Characterization》2014,31(6):675-684
In this work, a new and facile strategy is developed to synthesize a single‐phase Eu3+‐doped mesoporous gadolinium oxide nanorods (MS‐Gd2O3:Eu@PEG) by incorporating a facile wet‐chemical route, which includes an induced silica layer being coated onto the nanorods, and evolution of pores and formation of channels, as well as a surface‐modified process for multimodal imaging and anti‐cancer drug delivery. The properties of these as‐prepared Gd2O3:Eu nanorods are characterized by transmission electron microscopy (TEM), X‐ray diffraction (XRD), N2 adsorption/desorption, and photoluminescence (PL). The in vitro cytotoxicity test, drug loading, and drug release experiments reveal that the MS‐Gd2O3:Eu@PEG nanorods have good biocompatibility, efficient loading capacity, and pH‐sensitive releasing behavior, suggesting the nanorods could be an ideal candidate as drug delivery vehicles for cancer therapy. Furthermore, the MS‐Gd2O3:Eu@PEG nanorods show clearly dose‐dependent contrast enhancement in T1‐weighted magnetic resonance images and can potentially be used as a T1‐positive contrast agent. These results indicate our prepared multifunctional mesoporous gadolinium oxide nanorods can serve as a promising platform for simultaneous anti‐cancer drug delivery and multimodal imaging. 相似文献
95.
Xie Huanyu Hao Qing Jin Hongchang Xie Shuai Sun Zhaowei Ye Yadong Zhang Chaohui Wang Dong Ji Hengxing Wan Li-Jun 《中国科学:化学(英文版)》2020,63(9):1306-1314
Because of its high theoretical specific capacity and low reduction potential, Li metal is considered to be key to reaching high energy density in rechargeable batteries. In this context, most of the research has focused on suppressing dendrite formation during Li deposition to improve the cycling reversibility and safety of the batteries. Here, covalent organic framework(COF)film coating on a commercial polypropylene separator is applied as an ion redistributor to eliminate Li dendrites. The COF crystallites consist of ordered nanochannels that hinder the movement of anions while allowing Li-ions to transport across,leading to a high Li-ion transference number of 0.77±0.01. The transport of Li-ions across the COF film can be considered to be analogous to beads passing through a Galton Board, a model that demonstrates a statistical concept of a normal distribution.Thus, an even distribution of Li-ions is obtained at the COF/Li metal interface. The controlled Li-ion flux yields a smooth Li metal surface after 1,000 h(500 times) of cycling, leading to a significantly improved cycling stability and reversibility, as demonstrated by Cu||Li half cells, Li||Li symmetric cells, and Li Fe PO_4||Li full cells. These results suggest that, following the principle of a Galton Board, nanopore insulators such as COF-based materials are effective ion distributors for the different energy storage or conversion systems. 相似文献
96.
Yun‐Lei Peng Chaohui He Tony Pham Ting Wang Pengfei Li Rajamani Krishna Katherine A. Forrest Adam Hogan Shanelle Suepaul Brian Space Ming Fang Yao Chen Michael J. Zaworotko Jinping Li Libo Li Zhenjie Zhang Peng Cheng Banglin Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(30):10315-10320
Simultaneous removal of trace amounts of propyne and propadiene from propylene is an important but challenging industrial process. We report herein a class of microporous metal–organic frameworks ( NKMOF‐1‐M ) with exceptional water stability and remarkably high uptakes for both propyne and propadiene at low pressures. NKMOF‐1‐M separated a ternary propyne/propadiene/propylene (0.5 : 0.5 : 99.0) mixture with the highest reported selectivity for the production of polymer‐grade propylene (99.996 %) at ambient temperature, as attributed to its strong binding affinity for propyne and propadiene over propylene. Moreover, we were able to visualize propyne and propadiene molecules in the single‐crystal structure of NKMOF‐1‐M through a convenient approach under ambient conditions, which helped to precisely understand the binding sites and affinity for propyne and propadiene. These results provide important guidance on using ultramicroporous MOFs as physisorbent materials. 相似文献
97.
Three different kinds of silanols, which include isolated silanol, silanol I (with the hydroxyl proton bonded to an oxygen atom in the adjacent layer) and silanol II (with the hydroxyl proton bonded to the non-bridging oxygen at the same silicon atom), are generated during the hydration process of SKS-6 (δ-Na2Si2O5). 1H–1H nuclear Overhauser enhancement spectroscopy reveals that the proton of silanol I has an effective chemical exchange or spin diffusion with the proton of hydrogen-bonded water, while the proton of silanol II is likely far away from the other proton-containing species. 29Si magic angle spinning, 1H→29Si CP/MAS NMR and 1H–29Si phase-modulated Lee–Goldburg decoupled correlation experiments demonstrate that the local environments of the silicon sites in the final hydrated sample are mainly composed of Q2 [(SiO)2Si(OH)O−Na+], Q3 [(SiO)3Si(OH) and (SiO)3SiO−Na+] and Q4 [Si(OSi)4] groups. 相似文献
98.
Yang J Zhang M Deng F Luo Q Yi D Ye C 《Chemical communications (Cambridge, England)》2003,(7):884-885
Detailed structure of Br?nsted acid sites on the surface of SO3/Al2O3 catalyst has been proposed based on 1H/27Al TRAPDOR NMR results and the acidity of the catalyst has also been characterized by NMR probe molecules. 相似文献
99.
100.
Chaohui ZHANG 《数学年刊B辑(英文版)》2007,28(1):55-66
Let S be a Riemann surface with genus p and n punctures. Assume that 3p - 3 n > 0 and n ≥ 1. Let a be a puncture of S and let (~S) = S ∪ {a}. Then all mapping classes in the mapping class group Mods that fixes the puncture a can be projected to mapping classes of Mod(~S) under the forgetful map. In this paper the author studies the mapping classes in Mods that can be projected to a given hyperbolic mapping class in Mod(~S). 相似文献