粗糙化银电极上氰基钴胺素的电化学行为

比较研究氰基钴胺素在光滑和粗糙化银电极上的电化学行为，发现在光滑银电极上氰基钴胺素的还原为一个二电子过程，而在粗糙化银电极上则为两个一电子过程，其原因是由于粗糙化银电极对氰根的强吸附作用。     

Approximate expressions of determining the double layer energy and force of interaction between two charged colloidal spheres

The approximate expressions have been obtained to calculate the electrical double layer energy and force between two spherical colloidal particles based on the improved Derjaguin approximation. Results for identical spheres interacting under constant surface potential, constant surface charge are given. Comparison of present results with numerical results calculated by Carnie and Chan is made. The expressions are found to work quite well for the constant surface potential case, and for the constant charge case, we make correction for the expressions. The results given are satisfactory providedkh0.4.     

Highly stereoselective synthesis of 2,5-disubstituted 3-vinylidene tetetrahydrofurans via Prins-type cyclization

[reaction: see text]. A novel synthetic methodology for 2,5-disubstituted tetrahydrofurans having an allenyl group at the 3-position via Prins-type cyclization was developed. The reaction led to excellent selectivity and moderate to high yields.     

Determination of different forms of human interferon-gamma in single natural killer cells by capillary electrophoresis with on-capillary immunoreaction and laser-induced fluorescence detection

A novel method for determining different forms of human interferon-gamma (IFN-gamma) in single natural killer cells was developed by capillary electrophoresis (CE) with on-capillary immunoreaction and laser-induced fluorescence (LIF) detection. Cells were perforated with digitonin and one single cell was electrokinatically introduced into the front end of a separation capillary. The monoclonal antibody labeled with fluorescein isothiocyanate of IFN-gamma was hydrodynamically injected into the front end of the capillary around the cell introduced. After the cell was lysed by ultrasonication, the front end of the capillary was used as a microreactor to allow different forms of IFN-gamma to process the immunoreaction with their labeled antibody. Finally, the complexes of different forms of IFN-gamma with their labeled antibody were separated and detected by CE with LIF detection with a limit of detection of zeptomoles (10(-21) mol).     

Electrically conducting electrospun silk membranes fabricated by adsorption of carbon nanotubes

We present a simple method of obtaining electrically conducting electrospun silk non-woven membranes consisting of nanofibers with multi-walled carbon nanotubes (MWCNTs) adsorbed on their surface. Nanofibrous membranes with fibroin diameters of 460 ± 40 nm were formed from aqueous Bombyx mori fibroin solution by electrospinning. The MWCNTs adhered well to the surface of the highly porous silk nanofibrous membranes when Triton X-100 was used as the surfactant for the dispersion of the MWCNTs in aqueous media. The electrical conductivity of the membranes was 2.4 × 10⁻⁴ S/cm due to the presence of the MWCNTs on their surface. In addition, the strong interaction between the MWCNTs and nanofibers keeps them from separating each other, even after ultrasonication. The combination of the high conductivity of the membranes and the simple process used to fabricate them could lead to significant advances in the development of new materials, such as electromagnetic interference shielding or electrostatic dissipation membranes.     

Single‐Crystalline and Near‐Monodispersed NaMF3 (M=Mn,Co, Ni,Mg) and LiMAlF6 (M=Ca,Sr) Nanocrystals from Cothermolysis of Multiple Trifluoroacetates in Solution

We report the synthesis of single‐crystalline and near‐monodispersed NaMF₃ (M=Mn, Co, Ni, Mg), LiMAlF₆ (M=Ca, Sr), and NaMgF₃:Yb,Er nanocrystals (quasisquare nanoplates, nanorods, and nanopolygons) by the cothermolysis of multiple trifluoroacetates in hot combined organic solvents (oleic acid, oleylamine, and 1‐octadecene). The nanocrystals were characterized by XRD, TEM, superconductive quantum interference device (SQUID), and upconversion luminescence spectroscopy. By regulating the polarity of the dispersant, the NaMF₃ (M=Mn, Co, Ni) nanoplates were partially aligned to form nanoarrays on copper TEM grids. The sizes of the NaMF₃ nanocrystals were easily tuned by the use of proper synthetic conditions such as reaction temperature and time and solvent composition. On the basis of a series of experiments in which the reaction conditions were varied, together with GC–MS and FTIR analysis, the reaction pathways for the formation of these nanocrystals from trifluoroacetate precursors were proposed. The magnetic measurements showed that the differently sized NaMnF₃ square plates displayed interesting weak ferromagnetic behavior on the nanometer scale. The strong red upconversion luminescence emitted from the NaMgF₃:Yb,Er nanorods under 980‐nm near‐IR laser excitation suggests that NaMgF₃ may be a good candidate host material for red upconversion luminescence.     

Determination of Levofloxacin in Human Urine with Capillary Electrophoresis and Fluorescence Detector

In this study, we developed an analytical method for the enantioseparation of ofloxacin, using capillary electrophoresis with fluorescence detection. The optimum background electrolyte was obtained to be 60 mM hydroxylpropyl‐β‐cyclodextrin (HP‐β‐CD) in 50 mM phosphate buffer at pH 2.30. Under these conditions, the (+) and (‐) ofloxacin were completely separated, with the detection limit of 10 nM when the sample was prepared in deionized water. The linear ranges of levofloxacin in deionized water and untreated urine were 10^?7 to 5 × 10^?3 M with R² = 0.9989 and 5 × 10^?6to 5 × 10^?3 M with R² = 0.9943, respectively. We also applied this method to investigate the purity of a commercial drug. The results revealed that the ratio between (+)‐ofloxacin and (‐)‐ofloxacin (levofloxacin) was 99.9:0.1, and there is about 93 mg levofloxacin per tablet (200 mg). The concentration of levofloxacin in patient's urine was founded to be 7.9 × 10^?4M, and the ratio between the two optical isomers was 99.3:0.7.     

Helicity‐Encoded Molecular Strands: Efficient Access by the Hydrazone Route and Structural Features

Control over the folding of molecular strands may be achieved by appropriate choice of the constituting subunits, in particular for chains of specific heterocycles such as sequences of directly connected pyridine (py) and pyrimidine (pym) rings, which are known to fold into extended helical structures. Since the hydrazone (hyz) group represents an isomorphic analogue of a py site, the condensation of hydrazine and carboxaldehyde derivatives of pym offers a very efficient approach to strands incorporating hyz instead of py units and constituted by sequences of alternating hyz and pym groups. A series of such strands of different lengths, up to ten hyz units, i.e., 1 – 7 , were synthesized. Their spectral properties indicate that they fold indeed into helical shapes. Extensive characterization was performed in solution by ¹HNMR spectroscopy and in the solid state by determination of the crystal structures of eight such strands. They all display the expected helical geometry with up to 3 ¹/₃ turns and direct stacking contacts. The efficiency and flexibility of the synthetic approach as well as its wide potential for generation of diversity through lateral decoration make the (hyz? pym) subunit a particularly attractive helicity codon.     

Preparation ,Structural Characterization and Luminescent Property of Binucleasr Silver（Ⅰ）Complex Formed by Benzotriazole and 1—Hydroxymethyl Benzotriazole

Dinuclear silver (I) six‐membered ring complex [Ag₂ (bta)₂ ‐(hmbta)₂] (ClO₄)₂ (3) has been synthesized by the reaction of benzotriazole (bta) (1) and 1‐hydroxymethyl benzotriazole (hmbta) (2) with Ag (CH₃CN)₄ClO₄. The structures of compound 2 and Complex 3 have been studied by single crystal X‐ray diffraction analysis. The change of luminescent intensity of 1, 2 and 3 was reported. Compound 2 crystallizes in the monoclinic system with space group P2 (1)/c, a = 0.7655 (10) nm, b = 1.0126 (14) nm, c =0.9502 (13) nm, β = 95.07 (2)°, V = 0.7337 (17) nm³ and Z = 4. Complex 3 crystallizes in the triclinic system with space group P1, a = 0.73611 (18) nm, b = 0.9152 (2) nm, c = 1.2277 (3) nm, β = 87.170 (5)°, V = 0.8221 (3) nm³ and Z = 1. The main structural feature of complex 3 is a symmetric dinuclear six‐membered ring formed by two silver (I) atoms and four N‐atoms from two benzotriazoles. The second structural feature of complex 3 is the τ‐τ stacking interaction between two adjacent molecular planes, which forms the two‐dimentional layer structure. Besides, compared with 2, the luminescent intensity of complex 3 shows a remarkable enhancement.     

Catalytic combustion of chlorobenzene over V2O5/TiO2 catalysts prepared by the precipitation-deposition method

Catalytic combustion of chlorobenzene over supported vanadium oxides has been investigated. TiO₂ was prepared by the sol-gel method from titanium isopropoxide. The supported vanadium oxide catalysts have been prepared by precipitation-deposition and impregnation method and characterized by XRD, FT-Raman and TPR. In the VO_x/TiO₂catalysts prepared using the impregnation method, when vanadium loading reaches 3 wt.%, the activity shows a maximum. However, in the VO_x/TiO₂catalysts prepared by precipitation-deposition, when vanadium loading reaches 7 wt.%, the activity shows a maximum. This result suggests that the precipitation-deposition can yield a higher metal loading on the support and a high dispersion compared to the impregnation method. This revised version was published online in August 2006 with corrections to the Cover Date.