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81.
82.
Abachi S Baringer P Bylsma BG DeBonte R Koltick D Loeffler FJ Low EH McIlwain RL Miller DH Ng CR Rangan LK Shibata EI Derrick M Gan KK Kooijman P Loos JS Musgrave B Price LE Repond J Sugano K Weiss JM Wood DE Blockus D Brabson B Brom J Jung C Ogren H Rust DR Akerlof C Chapman J Errede D Kesten P Meyer DI Nitz D Seidl AA Thun R Willutzky M Cork B 《Physical review letters》1986,57(16):1990-1993
83.
Lin CS Zhang RQ Lee ST Elstner M Frauenheim T Wan LJ 《The journal of physical chemistry. B》2005,109(29):14183-14188
The assembly of small water clusters (H2O)n, n = 1-6, on a graphite surface is studied using a density functional tight-binding method complemented with an empirical van der Waals force correction, with confirmation using second-order M?ller-Plesset perturbation theory. It is shown that the optimized geometry of the water hexamer may change its original structure to an isoenergy one when interacting with a graphite surface in some specific orientation, while the smaller water cluster will maintain its cyclic or linear configurations (for the water dimer). The binding energy of water clusters interacting with graphite is dependent on the number of water molecules that form hydrogen bonds, but is independent of the water cluster size. These physically adsorbed water clusters show little change in their IR peak position and leave an almost perfect graphite surface. 相似文献
84.
G. X. Zheng Q. F. Wang S. G. Luo 《Journal of Radioanalytical and Nuclear Chemistry》2003,258(3):693-696
Four new complexes of UO2(II) and Th(IV) with bis-Schiff bases, derived from N,N'-bis[(l-phenyl-3-methyl-5-oxo-4-pyrazolinyl)-a-furylmethylidyne]-1,2-propylenediimine [1,2-BPMOPFP-H2] and N,N'- bis[(l-phenyl-3-methyl-5-oxo-4-pyrazolinyl)-a-furylmethylidyne]-1,3-propylenediimine [1,3-BPMOPFP-H2], were synthesized and characterized by elemental analysis, IR, UV, 1HNMR spectroscopy, and molar conductivity. The general formula of the complexes was confirmed to be [UO2(BPMOPFP)], [Th(BPMOPFP)(NO3)]NO3. A possible structure for the complexes have been proposed. 相似文献
85.
The covalent binding of acrylonitrile (CH(2)=CH-C triple bond N) and the formation of a C=C-C=N structure on Si(100) have been investigated using high-resolution electron energy loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and density functional theory (DFT) calculations. For chemisorbed acrylonitrile, the absence of nu(C triple bond N) at 2245 cm(-1) and the appearance of nu(C=N) at 1669 cm(-1) demonstrate that the cyano group directly participates in the interaction with Si(100), which is further supported by XPS and UPS observations. Our experimental results and DFT calculations unambiguously demonstrate a [2 + 2] cycloaddition mechanism for acrylonitrile chemisorption on Si(100) through the binding of C triple bond N to Si dimers. The resulting chemisorbed monolayer with a C=C-C=N skeleton can serve as a precursor for further chemical syntheses of multilayer organic thin films in a vacuum and surface functionalization for in situ device fabrication. 相似文献
86.
Tian S.-J. Xi G.-X. Cheng Q.-T. Lou X.-D. Li J.-H. 《Journal of Thermal Analysis and Calorimetry》1998,53(3):825-833
The inclusion complex of benzaldehyde (BA) with β-cyclodextrin (β-CD) was prepared and was studied by thermal analysis and
X-ray diffractometry. The composition of the complex was identified by TG and elemental analysis as β-CD·BA·9H2O. TG and DSC studies showed that the thermal dissociation of β-CD·BA·9H2O took place in three stages: dehydration in the range 70-120°C; dissociation of β-CD·BA in the range 235-270°C; and decomposition
of β-CD above 280°C. The kinetics of dissociation of β-CD·BA in flowing dry nitrogen was studied by means of TG both at constant
temperature and at linearly increasing temperature. The results showed that the dissociation of β-CD·BA was dominated by a
one-dimensional random nucleation and subsequent growth process (A2). The activation energy E was 124. 8 kJ mol-1, and the pre-exponential factor A 5.04·1011 min-1.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
87.
Suitable analytical methodologies were developed allowing direct determination of As, Cu, Fe, Pb, Sb and Sn in alcohol fuel samples by electrothermal atomic absorption spectrometry. Different chemical modification approaches were tested and compared in terms of analytical performance and in practical terms. Experimental conditions were optimized allowing little sample dilution and use of calibration curves prepared with aqueous inorganic analyte standards. Methodologies were tested with analyte spiked alcohol samples. Good analyte recoveries from spiked alcohol samples, precision better than 10% and limits of detection in the sub μg l−1 range were achieved. 相似文献
88.
Liu GD Zhong TS Huang SS Shen GL Yu RQ 《Fresenius' Journal of Analytical Chemistry》2001,370(8):1029-1034
A renewable amperometric immunosensor based on the sol-gel technique has been constructed by dispersing graphite, complement 3 (C3) antiserum, and sol-gel at low temperature. The prepared immunosensor is rigid, porous, and has a renewable external surface. A competitive binding assay has been used to determine C3 in human serum with the aid of C3 labeled with horseradish peroxidase. The enzyme-labeled antigen can readily diffuse toward the encapsulated antibody, which retains its binding properties. The experimental conditions for the assay with the biocomposite, including the loading of C3 antiserum in the biocomposite, the amount of labeled C3 in incubation solution, incubation time, and temperature, have been optimized. Using C3 labeled with horseradish peroxidase, and o-AP as the substrate, amperometric detection at -150 mV (relative to the SCE) results in a linear detection range of 1.17-35.1 microg mL(-1), with a detection limit of 0.56 microg mL(-1). Serum samples have been assayed and the results demonstrate the feasibility of the proposed immunosensor for clinical analysis. The surface of the immunosensor can be renewed simply by polishing to obtain a fresh immunocomposite ready to use in a new competitive assay. 相似文献
89.
The CH3NH2 molecule has been considered as either an important intermediate in methane and ammonia mixtures or a precursor in methylamine and hydrogen mixtures in the synthesis of carbon nitride thin films. The fast Hydrogen (H) abstraction from CH3NH2 is an important process involved in the formation of HCN or CNH in the chemical vapor deposition (CVD) of carbon nitride thin films. The energetic and kinetic characteristics of the H abstraction reaction from CH3NH2 by atomic H used in CVD of beta-C3N4 were studied using ab initio direct dynamics methods for the first time. Two primary processes were identified for this reaction: H abstraction from the CH3 group and H abstraction from the NH2 group. On the basis of ab initio data, the rate constants of each channel have been deduced by canonical variational transition state theory with small-curvature tunneling correction over a wide temperature range of 200 to approximately 3000 K. The theoretical results were compared with available experimental data. 相似文献
90.
The biological effects of aluminium have received much attention in recent years. Speciation of Al is of basic relevance as it concerns its reactivity and bioavailability. A differential pulse voltammetry (DPV) procedure is proposed for speciation analysis of Al(III) in natural waters and biological fluids using six catechols (L-dopa, dopamine, epinephrine, norepinephrine, caffeic acid and o-benzenediol) as electroactive ligands. The decrease of the DPV anodic peak current for each catechol ligand is linear with the increase of Al concentration. This speciation analysis idea is based on the measurement of the complexation capacity, namely, different affinities of Al(III) for catechols and organic ligands under two pH conditions. The labile monomeric Al fraction (mainly inorganic aluminium) is determined at pH 4.6, while the total monomeric Al fraction is determined at pH 8.5. The principle for Al(III) speciation analysis by an electrochemical method is discussed. This sensitive and simple fractionation method is successfully applied to the speciation analysis of Al in natural waters and the results agree well with those of Driscoll's method. The speciation analysis of Al in biological fluids is also explored and the results are compared with those obtained by ultrafiltration and dialysis. Compared with other speciation protocols the electrochemical method possesses some remarkable advantages: rapidity, high sensitivity, cheap instrumentation and a simple operation procedure. 相似文献