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111.
《Electroanalysis》2005,17(8):668-673
A self‐sampling‐and‐flow biosensor was fabricated by sandwiching a nitrocellulose strip on the working electrode side of the double‐sided microporous gold electrodes and a wicking pad on the counter electrode side. The double‐sided microporous electrodes were formed by plasma sputtering of gold on a porous nylon substrate. Sample was taken up to the enzyme‐immobilized working electrode by the capillary action of the front nitrocellulose strip dipped into the sample solution, analyzed electrochemically at the enzyme‐immobilized electrode, and diffuses out to the backside wicking pad through the micropores of the electrodes, constituting a complete flow cell device with no mechanical liquid‐transporting device. Biosensor was formed by co‐immobilizing the glucose oxidase and electron transfer mediator (ferrocene acetic acid) on the thioctic acid self‐assembled monolayer‐modified working electrode. A typical response time of the biosensor was about 5 min with the sensitivity of 2.98 nA/mM glucose, providing linear response up to 22.5 mM. To demonstrate the use of self‐sampling‐and‐flow biosensor, the consumption rate of glucose in the presence of yeast was monitored for five days. 相似文献
112.
S. N. Shkerin Yu. V. Sokolova S. M. Beresnev 《Russian Journal of Electrochemistry》2005,41(8):849-857
The polarization dependences of a porous gold electrode in contact with a solid electrolyte of the composition La0.88Sr0.12Ga0.82Mg0.18O2.85 are studied at 600–800°C and oxygen pressures of 2 × 10−2-1 atm. It is shown that the rate of cathodic reduction of oxygen out of the gas phase depends on the preliminary treatment of the sample. The activation energy is equal to 110–135 kJ mol−1 at a low polarization. After increasing the polarization, the activation energy for the cathodic reduction of oxygen equals 75–85 kJ mol−1 and depends on the oxygen pressure as a power function with a power index of 1/4. The rate of the anodic evolution of oxygen is dependent neither on the preliminary treatment of the sample nor on the oxygen pressure in the gas phase and the polarization curve has a characteristic segment, which corresponds to a limiting overvoltage.__________Translated from Elektrokhimiya, Vol. 41, No. 8, 2005, pp. 954–962.Original Russian Text Copyright © 2005 by Shkerin, Sokolova, Beresnev. 相似文献
113.
114.
《Surface and interface analysis : SIA》2003,35(5):429-431
Polycrystalline gold–nickel thin films are deposited on silicon (111) wafers by evaporation in a vacuum of 2 × 10?6 mbar. Concentration profiles of heat‐treated specimens are obtained by Auger electron depth profiling. The heat treatments are carried out in a vacuum furnace of 4 × 10?6 mbar in the temperature interval 473–773 K. The grain boundary diffusion coefficient is determined, using a modified Wipple model, to be (3 × 10?4 cm2 s?1) exp (?0.94 eV kT?1). It is concluded that interdiffusion in the investigated system is characterized by type B kinetics, and that grain boundary diffusion plays a dominant role in the mass transport process of such films. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
115.
Superoxide sensor based on cytochrome c immobilized on mixed-thiol SAM with a new calibration method
B GeF Lisdat 《Analytica chimica acta》2002,454(1):53-64
Cytochrome c was immobilized on a mixed-thiol (mercaptoundecanoic acid/mercaptoundecanol) modified gold electrode (MUA:MU/cyt c electrode). Characterization of the cyt c electrode showed a quasi-reversible, electrochemical redox behavior with a formal potential of −13±5 mV (versus Ag/AgCl) for the surface adsorbed protein and 3±5 mV for covalently immobilized cyt c. The heterogeneous electron transfer rate constants were determined to be about 70 and 40 s−1 for both states of the protein, respectively. They were found to be significantly higher than those of pure MUA-modified cyt c electrodes (MUA/cyt c electrodes). The interaction of superoxide radicals (O2−) with the (MUA:MU)/cyt c electrode was characterized and used for an amperometric O2− detection. The influence of H2O2 and uric acid on the sensor signal was investigated. The sensitivity of the (MUA:MU)/cyt c electrode to O2− was significantly improved compared with that of the MUA/cyt c electrode. Based on a kinetic model for the superoxide detection system, a new calibration method was established. This simple and fast method used the spontaneous dismutation of KO2 and was compared with the enzymatic superoxide generation system using xanthine oxidase. 相似文献
116.
Larsson S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(21):5276-5283
High-temperature superconductivity exists in layered, square-planar cuprates, but is almost absent in most other Cu(II) compounds and in most Ag(II) and Au(II) compounds. Valence state II is quite unusual in silver and gold and often disproportionates to valence states I and III ("negative-U compounds"). The two-electron difference in oxidation state is suggestive of electron pairing, a prerequisite for superconductivity. In the present paper the connection between disproportionation and geometrical structure on one hand and superconductivity on the other is discussed by using the accepted theory for mixed valence complexes. It is concluded that absence of superconductivity in gold and silver compounds can be connected to the instability of oxidation state II and the large difference in equilibrium geometry between oxidation states I and III. 相似文献
117.
A. S. Saghiyan A. V. Geolchanyan L. L. Manasyan G. M. Mkrtchyan N. R. Martirosyan S. A. Dadayan T. V. Kochickyan V. S. Harutyunyan A. A. Avetisyan V. I. Tararov V. I. Maleev Yu. N. Belokon' 《Russian Chemical Bulletin》2004,53(4):932-935
An efficient method was developed for the asymmetric synthesis of (R)-S-(1,2,4-triazol-3-yl)cysteines by the addition of 3,4-disubstituted 1,2,4-triazole-5-thiols at the electrophilic C=C bond in a NiII complex of a Schiff base of dehydroalanine with (S)-N-(N-benzylprolyl)aminobenzophenone. The stereoselectivity of the formation of diastereomeric complexes with the (S,R) configuration under conditions of thermodynamic control of the nucleophilic addition exceeds 94%. Acid treatment of the reaction mixtures afforded enantiomerically pure (R)-S-hetarylcysteines (ee >98%). 相似文献
118.
V. N. Tsarev S. E. Lyubimov S. V. Zheglov A. A. Shiryaev V. A. Davankov K. N. Gavrilov 《Russian Chemical Bulletin》2004,53(9):2025-2028
A chiral P,N-bidentate aryl phosphite ligand containing peripheral (R)-(+)-camphor-derived ketimine and its rhodium(I) and palladium(II) chelate complexes were synthesized for the first time. These compounds were found to be suitable for asymmetric allylic substitution. The Pd-catalyzed sulfonylation of 1,3-diphenylallyl acetate with sodium p-toluenesulfinate gave the product in 73% ee; in the alkylation of the same substrate with dimethyl malonate, the ee was 94%. These ee values are higher than the enantioselectivity achieved with the known phosphine analogs.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1942–1945, September, 2004. 相似文献
119.
Novel meander with Co3+ und Au3+: Na4[AuCoO5] = Na8 1∞ [(O2/2 (CoO)O2AuO2/2)2] By “reaction with the wall” we obtained for the first time transparent brown single crystals of Na4[AuCoO5] while heating intimate mixtures of Co3O4, Na2O2, and K2O2 (Co: Na: K = 1.00:4.91:2.20; 650°C/44d) in a sealed gold-tube: monoclinic, P21/m, with a = 555.69(4) pm, b = 1042.11 (8) pm, c = 555.69(4) pm, β = 117.387(5)°, Z = 2. Characteristic features of Na4[AuCoO5] are meandric chains [(O2/2 (CoO)O2AuO2/2)2]. The structure has been determined by four-circle diffractometer data (Siemens AED 2; Mo? Kα , graphite, 881 I0(hkl), R = 0.0366, Rw = 0.0316), parameters as given in the text. The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, these via Mean Fictive Ionic Radii, and Charge-distribution, CHARDI, are calculated and discussed. 相似文献
120.
A novel enantiopure 1,2-diamine (5) having two phenolic hydroxy groups was attached into chloromethylated polystyrene through benzyl ether linkage, which was used as a chiral ligand of the catalyst in asymmetric hydrogenation of acetophenone. 相似文献