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981.
Gian Luigi Bendazzoli 《Theoretical chemistry accounts》2007,118(1):135-142
We present and discuss a variational single-product approximation to the van der Waals dispersion interaction leading to a
simple formula for C
6 that seems capable to give more than 99% of the ‘exact’ value. The formula is derived from Hylleraas’ variational principle
in the tensor product space of the interacting molecules and therefore enjoys bounding properties. The formula has been tested
by computing the C
6 dispersion constants of H–H, and, at Full CI level, of the following systems: He–He, He–Li, Li–Li, LiH–LiH, HF–HF. Connections
with the London formula are discussed.
Contribution to the Fernando Bernardi Memorial Issue. 相似文献
982.
Shahriare Ghammamy Monir Rahnama Baghy Wong Wing-Tak Kheiroallah Mehrani Saied Maleki 《Transition Metal Chemistry》2007,32(2):257-261
The complex of propyltriphenylphosphonium bromochromate(VI), PrPh3P[CrO3Br] is easily synthesized in nearly quantitative yield using a direct reaction of chromium(VI) oxide and propyltriphenylphosphonium
bromide. This compound is a versatile reagent for the efficient and selective oxidation of organic substrates, in particular
for alcohols to their corresponding aldehydes or ketones, under mild conditions. This compound was characterized by IR, UV/Visible,
13C-n.m.r. and 1H-n.m.r. techniques. It crystallized in the monoclinic form and its crystal and molecular structure have been determined by
X-ray crystallography. 相似文献
983.
Microwave synthesis,characterization and catalytic properties of titanium-incorporated ZSM-5 zeolite
Taihuan Jin Young Kyu Hwang Do-Young Hong Sung Hwa Jhung Jin-Soo Hwang San-Eon Park Young Ho Kim Jong-San Chang 《Research on Chemical Intermediates》2007,33(6):501-512
Titanium-incorporated ZSM-5 zeolites (Si/Al = 50–200 and Si/Ti = 70) were successfully synthesized in a one-step sol-gel process
under microwave irradiation. The characteristics of Ti-ZSM-5 zeolites were investigated using X-ray power diffraction, UV/Vis-DRS,
FT-IR spectroscopy and solid-state 27Al-NMR to monitor the physico-chemical properties. Simultaneously, the acidic properties were characterized by the NH3-TPD profile. The characterization results revealed that the Ti4+ and Al3+ ions were well incorporated into the framework of Ti-ZSM-5 zeolite. The prepared zeolite was moderately active but selective
in the dehydration of methanol to dimethyl ether. 相似文献
984.
仲碳伯胺萃淋树脂吸萃金的性能及机理 总被引:3,自引:0,他引:3
研究了仲碳伯胺(N1923)萃淋树脂吸萃金的机理,溶液酸效应、吸附等温线、吸附速率、盐析剂效应及柱操作条件的影响等,将该树脂用于矿样中金含量的测定,结果与717^#离子交换树脂吸附法一致,取得了较好的结果。 相似文献
985.
986.
987.
Oleg V. Mikhailov Marina A. Kazymova Tatyana A. Shumilova Galina A. Chmutova Svetlana E. Solovieva 《Transition Metal Chemistry》2005,30(3):299-304
The complexing process proceeding in the NiII–thiocarbohydrazide (H2N–H–NC(=S)–NH–NH2)–propanone triple system in EtOH solution and nickel(II)hexacyanoferrate(II) gelatin-immobilized matrix has been studied. It has been found that in the first case, template synthesis leading, as a minimum, to formation of three coordination compounds of NiII with (N,N,S,S)-donor tetradentate ligands having NiL1, NiL2 and NiL3compositions where L1 is 4,6,6-trimethyl-2,3,7,8-tetraazanonen-3-di(thiohydrazide)-1,9, L2 is 4,6,6,12-tetrametyl-1,9-dithio-2,3,7,8,10,11-hexaazatridekadien-3,11-hydrazide-1 and L3 is 2,8,10,10,16-pentamethyl-5,13-dithio-3,4,6,7,11,12,14,15-octaazaheptadekatrien-2,7,15 is observed, whereas in the gelatin-immobilized matrix, a complexing process in the system considered does not occur. 相似文献
988.
989.
Yuan Ruo Cao ShuRui Chai YaQin Gao FengXian Zhao Qing Tang MingYu Tong ZhongQiang Xie Yi 《中国科学B辑(英文版)》2007,50(5):620-628
Alternate adsorption of positively charged colloid-Au nanoparticles (nano-Au⊕) and negatively charged hemoglobin (Hb) on L-cysteine (L-cys) modified gold electrode resulted in the assembly of {Hb/nano-Au⊕}n layer-by-layer films/L-cys modified gold electrode. The nano-Au⊕ was characterized by transmission electron micrograph (TEM) and microelectrophoresis. The modified electrode interface morphology was characterized by electrochemical impedance spectroscopy (EIS), atomic force mi- croscopy (AFM), cyclic voltammograms (CV) and chronoamperometry. Direct electron transfer between hemoglobin and gold electrodes was studied, and the apparent Michaelis-Menten constant ( km app) of the modified electrode was evaluated to be 0.10 mmol·L?1. Moreover, the higher activity of proteins in the nano-Au⊕ films could be retained compared with the electropolymerization membrane, since the pro- teins in nano-Au⊕ films retained their near-native structure. Direct electron transfer between hemoglo- bin and electrode and electrochemically catalyzed reduction of hydrogen peroxide on a modified elec- trode was studied, and the linear range was from 2.1×10-8 to 1.2 ×10?3 mol·L-1 (r = 0.994) with a detection limit of 1.1×10-8 mol·L-1 H2O2. 相似文献
990.
A beta-iron oxyhydroxide (FeOOH) was synthesized via a hydrolyzing route and investigated as a lithium intercalation host.
It delivers a capacity of about 170 mAh/g and exhibits good cycling performance when charged/discharged in the voltage range
from 1.6 V to 3.3 V. For the first time we have confirmed that FeOOH is suitable for using it as a negative electrode for
hybrid electrochemical supercapacitor assembled with an activated carbon positive electrode in 1.0 M LiPF6 ethylene carbonate/dimethyl carbonate (EC/DMC, 1:2 in volume) solution. The cell reveals a slightly sloping voltage profile
from 0 V to 2.8 V and gives an estimated specific energy of 45 Wh/kg based on the total weight of two electrode materials,
approximately two times of carbon/carbon electrochemical double layer capacitors. The hybrid supercapacitor shows a good cycling
performance, it remains approximately 96% of initial capacity after 800 cycles at a charge/discharge rate of 4 C. The capacitor
also shows a desirable rate capability, even at 10 C discharge rate, it holds 80% of capacity compared with that at 1 C discharge
rate. 相似文献