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201.
Han C Yan SS Lin XL Hu SJ Zhao MW Yao XX Chen YX Liu GL Mei LM 《Journal of computational chemistry》2011,32(7):1298-1302
First-principles calculations of undoped HfO(2) and cobalt-doped HfO(2) have been carried out to study the magnetic properties of the dielectric material. In contrast to previous reports, it was found that the native defects in HfO(2) could not induce strong ferromagnetism. However, the cobalt substituting hafnium is the most stable defect under oxidation condition, and the ferromagnetic (FM) coupling between the cobalt substitutions is favorable in various configurations. We found that the FM coupling is mediated by the threefold-coordinated oxygen atoms in monoclinic HfO(2) and could be further enhanced in electron-rich condition. 相似文献
202.
The mechanical properties of hybrid framework materials, including both nanoporous metal-organic frameworks (MOFs) and dense inorganic-organic frameworks, are discussed in this critical review. Although there are relatively few studies of this kind in the literature, major recent advances in this area are beginning to shed light on the fundamental structure-mechanical property relationships. Indeed research into the mechanical behavior of this important new class of solid-state materials is central to the design and optimal performance of a multitude of technological applications envisaged. In this review, we examine the elasticity of hybrid frameworks by considering their Young's modulus, Poisson's ratio, bulk modulus and shear modulus. This is followed by discussions of their hardness, plasticity, yield strength and fracture behavior. Our focus is on both experimental and computational approaches. Experimental work on single crystals and amorphized monoliths involved primarily the application of nanoindentation and atomic force microscopy to determine the elastic moduli and hardness properties. The compressibility and bulk moduli of single crystals and polycrystalline powders were studied by high-pressure X-ray crystallography in the diamond anvil cell, while in one instance spectroscopic ellipsometry has also been used to estimate the elastic moduli of MOF nanoparticles and deposited films. Theoretical studies, on the other hand, encompassed the application of first principles density-functional calculations and finite-temperature molecular dynamics simulations. Finally, by virtue of the diverse mechanical properties achievable in hybrid framework materials, we propose that a new domain be established in the materials selection map to define this emerging class of materials (137 references). 相似文献
203.
Vapor pressure data were measured for nine binary systems containing water, ethanol, or methanol with one of three protonic ionic liquids (PILs), viz. mono-, di- and tri-ethanolammonium tetrafluoroborate ([HMEA][BF4], [HDEA][BF4], and [HTEA][BF4]), at varying temperatures and PIL-contents using a quasi-static ebulliometer. The vapor pressure data were correlated by NRTL model with an overall average absolute relative deviation (AARD) of 0.0175. It is showed that the effect of PILs on the vapor pressure lowering of solvents follows the order of [HMEA][BF4] > [HDEA][BF4] > [HTEA][BF4], and the vapor pressure lowering degree follows the order of water > methanol > ethanol. Besides, the activity coefficients of solvent for binary system {solvent + PIL} at fixed PIL mole fraction of 0.10 were calculated using the regressed NRTL parameters. The results indicate that three PILs can give rise to a negative deviation from the Raoult's law for water and methanol and a positive deviation for ethanol to a varying degree, leading to the variation of relative volatility of a solvent. 相似文献
204.
205.
Liu X Xu D Lu R Li B Qian C Xue P Zhang X Zhou H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(5):1660-1669
A series of new triphenylamine-functionalized bis(β-diketone)s bridged by a carbazole (CnBDKC, n=1, 4, 8, 16) with twisted intramolecular charge-transfer emission in polar solvents has been synthesized. The length of the carbon chains has a significant effect on the self-assembling properties of the compounds. Well-defined 1D nanowires were easily generated from C1BDKC with a methyl group by a reprecipitation approach directed by π-stacking interaction, and the molecules packed into J-aggregates in the nanowires. In addition, 1D nanofibers based on C16BDKC bearing a long hexadecyl chain were prepared through the organogelation process, and H-aggregates were formed driven by the synergistic effect of π-stacking interaction and van der Waals force in the gel phase. C4BDKC and C8BDKC containing butyl and octyl side chains, respectively, cannot arrange into dispersed nanostructures, probably because π-π interaction between conjugated moieties might be disturbed by the interaction between the side chains, which is, however, not strong enough to dominate the self-assembling process. Notably, the nanowires based on C1BDKC and the gel nanofibers from C16BDKC can emit strong green light under irradiation, which suggests that these 1D nanomaterials may have potential applications in emitting materials as well as photonic devices. 相似文献
206.
New microporous metal-organic framework demonstrating unique selectivity for detection of high explosives and aromatic compounds 总被引:1,自引:0,他引:1
Pramanik S Zheng C Zhang X Emge TJ Li J 《Journal of the American Chemical Society》2011,133(12):4153-4155
A highly luminescent three-dimensional microporous metal-organic framework, [Zn(2)(oba)(2)(bpy)]·DMA, demonstrates unique selectivity for the detection of high explosives and other aromatics via a fluorescence quenching and enhancement mechanism. 相似文献
207.
金属辅助化学腐蚀法可以在无外加电路的条件下,在40%HF/30%H2O2/乙醇的混合溶液中完成多孔硅的制备,该方法简单快速。本文研究了金属辅助法腐蚀液体系各组分(HF、H2O2、乙醇)含量对多孔硅表面的SiHx成分和多孔层结构的影响,根据Si-H和Si-O的红外吸收峰强度的变化曲线优化了腐蚀液体系中各组分含量。在腐蚀液各组分体积比为V40%HF∶V30%H2O2∶V乙醇=2∶2∶1和腐蚀时间为4 min的条件下制备了形貌均匀、化学活性(SiHx成分)和多孔结构稳定性较好的多孔硅,并对金属辅助法与阳极蚀刻法制得的两种多孔硅进行比较,结果显示金属辅助法制备的多孔硅的化学活性和稳定性在后续的生物技术应用中具有明显的优越性。 相似文献
208.
Chong SL Nissilä T Ketola RA Koutaniemi S Derba-Maceluch M Mellerowicz EJ Tenkanen M Tuomainen P 《Analytical and bioanalytical chemistry》2011,401(9):2995-3009
The atmospheric pressure matrix-assisted laser desorption/ionization with ion trap mass spectrometry (AP-MALDI-ITMS) was investigated
for its ability to analyse plant-derived oligosaccharides. The AP-MALDI-ITMS was able to detect xylooligosaccharides (XOS)
with chain length of up to ten xylopyranosyl residues. Though the conventional MALDI–time-of-flight/mass spectrometry (TOF/MS)
showed better sensitivity at higher mass range (>m/z 2,000), the AP-MALDI-ITMS seems to be more suitable for detection of acetylated XOS, and the measurement also corresponded
better than the MALDI-TOF/MS analysis to the actual compositions of the pentose- and hexose-derived oligosaccharides in a
complex sample. The structures of two isomeric aldotetrauronic acids and a mixture of acidic XOS were elucidated by AP-MALDI-ITMS
using multi-stages mass fragmentation up to MS3. Thus, the AP-MALDI-ITMS demonstrated an advantage in determining both mass and structures of plant-derived oligosaccharides.
In addition, the method of combining the direct endo-1,4-β-d-xylanase hydrolysis of plant material, and then followed by AP-MALDI-ITMS detection, was shown to recognize the substitution
variations of glucuronoxylans in hardwood species and in Arabidopsis thaliana. To our knowledge, this is the first report to demonstrate the acetylation of glucuronoxylan in A. thaliana. The method, which requires only a small amount of plant material, such as 1 to 5 mg for the A. thaliana stem material, can be applied as a high throughput fingerprinting tool for the fast comparison of glucuronoxylan structures
among plant species or transformants that result from in vivo cell wall modification. 相似文献
209.
210.
Min Zhou Min Xu Dong Wang Hong‐Tao Zhu Chong‐Ren Yang Ying‐Jun Zhang 《Helvetica chimica acta》2011,94(11):2010-2019
Phytochemical investigation of the rhizomes of Panax japonicus C. A. Meyer (Araliaceae) resulted in the isolation of two new dammarane‐type triterpenoid saponins, yesanchinoside R1 ( 1 ) and yesanchinoside R2 ( 2 ), together with one new natural product, 6′′′‐O‐acetylginsenoside Re ( 3 ). In addition, 25 known compounds, including 23 triterpenoid saponins, 4 – 26 , β‐sitosterol 3‐O‐β‐D ‐glucopyranoside ( 27 ), and ecdysterone ( 28 ), were also identified. The known saponins 12, 15 , and 18 – 22 were reported for the first time from the title plant. Their structures were elucidated on the basis of detailed spectroscopic analyses, including 1D‐ and 2D‐NMR techniques, as well as acidic hydrolysis. 相似文献