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排序方式: 共有273条查询结果,搜索用时 0 毫秒
71.
Das SK Bhunia MK Motin Seikh M Dutta S Bhaumik A 《Dalton transactions (Cambridge, England : 2003)》2011,40(12):2932-2939
A new porous Co(II)-salicylate metal-organic framework material has been synthesized hydrothermally through the reaction of Co(II) chloride with sodium salicylate under mild alkaline pH conditions. To get an idea about the structural aspect of the material from the powder X-ray diffraction (PXRD) pattern, MAUD program has been successfully utilized and the assigned peaks match very well with a new tetragonal phase (space group, P4mm) having the unit cell parameters: a = b = 12.957 (0.042) ?; c = 12.738 (0.019) ?; α = β = γ = 90°, V = 2138.73 ?(3). N(2) adsorption/desorption analyses suggested the material is highly porous in nature having high BET surface area and pore dimensions of 2.0-3.0 nm, which is within the range of small mesopores. Thermogravimetric analysis (TGA) revealed that the H(2)O molecules may be removed from the framework without collapsing the structure and the material is stable up to ca. 573 K. The material is characterized thoroughly by using different characterization tools such as TEM, SEM, UV-visible reflectance spectroscopy, FT IR spectroscopy and photoluminescence spectroscopy. X-Ray photoelectron spectroscopic (XPS) analysis was employed to understand the oxidation state of the cobalt atom and presence of other elements within the framework. The material shows interesting magnetic properties, where the magnetic moments monotonically increase with the decrease in temperature down to 9 K. Below 9 K there is a steep increase in magnetization on further lowering the temperature, thereby suggesting the onset of a long range ferromagnetic transition with ferromagnetic Curie temperature, T(C) = 8.5 K. Furthermore, the M-H curve at 2 K shows a clear hysteresis loop with a coercive field 150 Oe and remnant magnetization 0.8 μ(B)/f.u. 相似文献
72.
Jammi S Rout L Saha P Akkilagunta VK Sanyasi S Punniyamurthy T 《Inorganic chemistry》2008,47(12):5093-5098
Chiral copper(II) coordination polymers 1a-c have been prepared by one-pot synthesis in high yield. Their single-crystal X-ray analysis showed that repeating units are connected to each other by carboxylate linker and copper(II) atoms are pentacoordinated with distorted square-pyramidal geometry for 1a-b and square-planar geometry for 1c. These polymers have catalyzed the kinetic resolution of secondary alcohols by acylation with up to 90% ee ( s = 50). 相似文献
73.
Golden opportunity: [4+3] Cycloaddition reactions of arenynamides and epoxides are enabled under gold catalysis and have a broad substrate scope (see scheme; Ms=methanesulfonyl). An S(N) 2-type front-side attack of phenyl at the oxiranyl ring is expected to cause the retention of stereochemistry. 相似文献
74.
75.
This paper demonstrates the use of copper electrode for the treatment of sugar processing industry wastewater (SPIW) in terms of chemical oxygen demand (COD) by applying electrocoagulation (EC) method. EC process was carried out in batch mode with electrode effective area of 0.0112 m2, supplied current intensity (CI) of 44.64 A/m2 - 223.21 A/m2, electrode gap (EG) of 0.5–2.5 cm, electrolyte (NaCl) dose (ED) of 0.5–2.5 g/L to treat SPIW with initial chemical oxygen demand (COD) of 6000 mg/L. The maximum COD removal 73% of SPIW is achieved at optimized condition of SPIW pH: 7, CI: 89.28 A/m2, EG: 1.5 cm & ED: 1.5 g/L. Sludge and scum generated during EC process were characterized by FTIR, TGA/DTA/DTG, proximate & ultimate analysis to find its applicability and their disposal. Additionally, economic study of EC treatment process at optimum condition suggest treatment cost was 11.2 US$/m3 and it indicate economic results as comparison to other available treatment processes. 相似文献
76.
Hari Shankar Parul Bansal Dr. William W. Yu Dr. Prasenjit Kar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(53):12242-12248
In the literature, lead halide perovskites are very notable for their degradation in the presence of polar solvents, such as water. In contrast, in this research, it is observed that adding a minor amount of water into the precursor solution can improve the stability and photoluminescence quantum yield of CsPbBr3 nanocrystals through a ligand-assisted reprecipitation (LARP) method. In this way, the shape and phase transformation from CsPbBr3 nanoplates to CsPbBr3/Cs4PbBr6 nanorods and Cs4PbBr6 nanowires can be controlled with increasing water content in the precursor solution. Upon adding water up to an ideal amount, CsPbBr3 maintains its phase and nanoplate morphology. The key role of water amount for tuning the crystallinity, stability, morphology, optical properties, and phase transformation of cesium lead halide perovskite nanocrystals will be beneficial in the future commercialization of optoelectronics. 相似文献
77.
An efficient method for the synthesis of 2,3,5,6-tetrasubstituted tetrahydropyrans has been developed from the reaction of aldehydes and ethyl 2-(1-hydroxyalkyl/hydroxy(phenyl)methyl)-5-methylhex-4-enoate using (3,5)-oxonium-ene reaction promoted by boron trifluoride etherate in good yields under mild conditions. 相似文献
78.
A new method of male contraception has been developed which results in long-term infertility and has the potential advantage of being reversible. The contraceptive, given the name RISUG (an acronym for Reversible Inhibition of Sperm Under Guidance) is a polyelectrolytic compound and when injected into the lumen of the vas deferens, induces a surface charge imbalance on the sperm membrane system leading to its destabilization. In the present study, morphological and topological alterations in human spermatozoa induced by RISUG have been investigated using atomic force microscopy (AFM). Complete disintegration of the plasma membrane with subsequent rupture and dispersion of the acrosomal contents is observed on treatment with RISUG in vitro. Considerable damage to the midpiece region with significant clustering of the mitochondria and its fusion with the head region is also observed. These observations are in agreement with the significant increase in the volume of RISUG-treated sperm-head region. Topological alterations in the flagellar and midpiece region of RISUG-treated spermatozoa have also been studied. 相似文献
79.
We report results of hyperpolarizability calculations on CdnXn (X: S, Se and Te; n = 1–10) clusters. Our results show that the geometric configurations of different types of clusters under
investigation are quite similar at specific values of n. Both static and frequency dependent components of first and second
order hyperpolarizability tensors of CdnSn, CdnSen and CdnTen are compared. It is observed that in general nonlinear optical coefficients show identical variation in all the cluster materials.
The present investigation also manifests the improvement of these coefficients due to the introduction of asymptotically correct
generalized gradient approximation functional over the local density functional and normal gradient corrected functional.
Symmetrized fragment orbital analysis has been performed to provide explanation of the observed hyperpolarizability variation.
We also analyse how geometries with closely lying energy values influence the hyperpolarizabilities of these cluster materials. 相似文献
80.
New urea-based sensors show a strong affinity for F−, CH3COO−, and H2PO4− with an appreciable color change in the presence of excess F−. The position of the nitro group in the urea derivative influences the relative affinity toward anionic analytes. Spectral and ab initio studies showed the difference in the deprotonation sites for the ortho- and meta/para-isomers in these cases. Photophysical studies confirmed the resonance energy transfer in the case of the ortho-isomer. The ortho-isomer can act as a dual emission probe for F−. 相似文献