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排序方式: 共有9521条查询结果,搜索用时 23 毫秒
941.
Electrochemical Detection of Anions on an Electrophoresis Microchip with Integrated Silver Electrode
《Electroanalysis》2005,17(13):1222-1226
A poly(dimethylsiloxane)/glass hybrid microfluidic chip with integrated silver electrode is described for electrochemical detection of anions. The working electrode was directly fabricated on a glass slide and the chip formed by reversibly sealing of a PDMS slab with microchannels to the slide. Under an alkaline phosphate condition, thiocyanide and three halides were sensitively detected. Factors influencing the separation and detection procedure were discussed and optimized. Linear responses over two magnitudes were obtained with limit of detection at the micromolar level. 相似文献
942.
Burkhard Butschke Maria Schlangen Detlef Schröder Helmut Schwarz 《Helvetica chimica acta》2008,91(10):1902-1915
Mechanistic details for the formation of methane from the title compound as well as the combined elimination of (CH3)2S/CH4 are derived from various mass‐spectrometric experiments including deuterium‐labeling studies and DFT calculations. For the first process, i.e., methane formation, we have identified three competing pathways in which the intact, Pt‐bonded methyl group combines with a H‐atom that originates from a phenyl substituent (ca. 7%), the dimethyl sulfide ligand (ca. 41%), and a methyl group of the diazabutadiene backbone (ca. 52%). In contrast, in the combined (CH3)2S/CH4 elimination, the methane is specifically formed from the Pt‐bound CH3 group and a H‐atom provided by one of the phenyl groups (‘cyclometalation’). 相似文献
943.
Chang‐Ying Yang Zhong‐Xu Dai Xin Li Fan‐Chong Rong 《Surface and interface analysis : SIA》2009,41(5):366-370
The gold electrode was modified by noisomes, prepared by sonicating the mixed solution of PEG 6000/Tween 80/Span 80/H2O. Electrochemical cyclic voltammetry (CV) and impedance spectroscopy (EIS) were performed for characterizing the modification. The construction of multilayer films of octadecanethiol (ODT)‐niosomes had almost no pinholes, which elicited that niosomes‐coated electrode through ODT assembly was more effective immobilization compared to direct modification method. A large semicircle formation in the entire range of frequency indicated the complete electron‐transfer control for the redox reaction, implying a perfect blocking behavior. The Nyquist plot was consisting of two depressed semicircles after storage for 36 h in air, which implied a progressive and uniform construction manner, as expected for porous coatings. The modified electrode was used to investigate the interaction between 1‐anilino‐8‐naphthalene‐sulfonate (ANS) and noisomes. It was found that the low‐frequency semicircular arcs increase in diameter, indicating that the increase in the resistance Rp attributed mainly to the niosomes/solution interface. It was due to the binding of ANS to the niosomes‐modified electrode surface, exhibited against diffusing species through the pores. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
944.
ATP determination is of great importance since this compound is involved in a number of vital biological processes. To monitor ATP concentration levels, we have developed a microbiosensor based on cylindrical platinum microelectrode, covered with a layer of poly-m-phenylendiamine (PPD), and layer of co-immobilised glucose oxidase and hexokinase. Conditions for biosensor measurement of ATP (pH, Mg2+ and substrates concentration) in vitro and microbiosensor characteristics such as sensitivity, selectivity, reproducibility, storage stability were studied and optimized. Under optimal conditions the microbiosensor can measure ATP concentrations down to a 2.5 μM detection limit with response time about 15 s. Interferences by electroactive compounds like biogenic amines and their metabolites, ascorbic acid, uric acid and l-cystein are rejected in general by the PPD layer. The microbiosensor developed is insensitive to ATP analogues (or substances with similar structure), such as ADP, AMP, GTP and UTP, too. It can be used for ATP analysis in vitro in the reactions consuming or producing macroergic triphosphate molecules to study kinetics of the process and in drug design concerning development of inhibitors specific to target kinases and others target enzymes. 相似文献
945.
In this article, electrochemistry of mitochondria is achieved. Cyclic voltammograms of freshly prepared mitochondria were obtained by immobilizing mitochondria together with glutaraldehyde and bovine serum albumin on the surface of a pyrolytic graphite electrode. Two pairs of redox peaks could be observed which were ascribed to the electron transfer reactions of cytochrome c and FAD/FADH2. Study of submitochondrial particles was also conducted, which could confirm the results of the study of the entire mitochondria. The redox wave of NADH could be obtained due to the destruction of the membrane of mitochondria. We have also checked the function of succinate in mitochondria by employing the electrochemical method. This work is not only the first to be able to obtain the direct electrochemistry of mitochondria, but is also beneficial to the further understanding of the structure and function of mitochondria in vitro. 相似文献
946.
Philippe De Taxis Du Poet Shigeyuki Miyamoto Toru Murakami Jun Kimura Isao Karube 《Analytica chimica acta》1990
Direct electron transfer between active glucose oxidase (GOD) and a gold electrode was obtained when GOD was immobilized in poly(N-methylpyrrole) electrochemically prepared on the gold electrode. When electropolymerization was accomplished at 50 °C, after glucose addition, the cyclic voltammograms showed an increased oxidation peak at ca. ?0.45 V vs. Ag/AgCl. This potential corresponds to the oxidation potential for FADH2. Although the GOD becomes much less selective, a glucose-dependent current response is obtained. 相似文献
947.
The relationship between the selectivity of six drug ion-selective electrodes with anionic species of hetero-poly acid as exchange site and the structural and thermodynamical parameters of the metal ion has been investigated experimentally and theoretically. The electrode selectivity is controlled mainly by the extractibility or hydrophobicity of the metal ion, but not by the ion-association-complex formation process. Linear relationship exists between the pK_(ij) value and the structural parameter z~2/(r + 0.85) and the thermodynamic parameter of hydration (△G_h) of the metal ion. Better correlation is obtained for the pK_(ij)vs. (z~2/r)~(-k) relationship. 相似文献
948.
M. Manolova V. Ivanova D.M. Kolb H.-G. Boyen P. Ziemann M. Büttner A. Romanyuk P. Oelhafen 《Surface science》2005,590(2-3):146-153
In this study we describe details of a new technique that allows to deposit metal on top of a self-assembled monolayer (SAM). Monoatomic high platinum islands were formed on a 4-mercaptopyridine SAM on Au(1 1 1) by first immersing the SAM-covered gold electrode in an aqueous solution of K2PtCl4 without potential control to allow Pt(II) ions to form a complex with the pyridine nitrogen. The complexed Pt(II) ions were then reduced electrochemically to Pt(0) after transferring the electrode to a Pt(II) ion-free solution. Upon reduction, monoatomic high Pt islands were observed in STM, the total coverage depending on the time for complexation. Ex situ angle-resolved XPS studies reveal that the Pt islands indeed reside on top of the SAM. 相似文献
949.
The time dependence of the concentration of CO2 in an electrochemical thin layer cavity is studied with Fourier transform infrared spectroscopy (FTIR) in order to evaluate
the extent to which the thin layer cavity is diffusionally decoupled from the surrounding bulk electrolyte. For the model
system of CO on Pt(111) in 0.1 M HClO4, it is found that the concentration of CO2, formed by electro-oxidation of CO, equilibrates rapidly with the surrounding bulk electrolyte. This rapid equilibration
indicates that there is diffusion out of the thin layer, even on the short time scales of typical infrared experiments (1–3 min).
However, since the measured CO2 absorbance intensity as a function of time is reproducible to within 10%, a new time-dependent method for surface coverage
calibration using solution-phase species is proposed.
Dedicated to Prof. Dr. Teresa Iwasita on the occasion of her 65th birthday in recognition of her numerous contributions to
interfacial electrochemistry. 相似文献
950.
Tongtao Wang Caishun Lin Feng Ye Yong Fang Jingjing Li Xindong Wang 《Electrochemistry communications》2008,10(9):1261-1263
Methanol permeation is one of the key problems for direct methanol fuel cell (DMFC) applications. It is necessary to change the structure of the cathode of membrane electrode assembly (MEA). Therefore, a novel MEA with double-layered catalyst cathode was prepared in this paper. The double-layered catalyst consists of PtRu black as inner catalyst layer and Pt black as outer catalyst layer. The inner catalyst layer is prepared for oxidation of the methanol permeated from anode. The results indicate that this double-layered catalyst reduced the effects of methanol crossover and assimilated mixed potential losses. The performance of MEA with double-layered catalyst cathode was 52.2 mW cm−2, which was a remarkable improvement compared with the performance of MEA with traditional cathode. The key factor responsible for the improved performance is the optimization of the electrode structure. 相似文献