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用电化学聚合法在多种烷基硫醇自组装膜修饰金电极上制备了聚吡咯.通过计时安培法、循环伏安法和交流阻抗技术研究了自组装膜的烷基链长和端基功能团对吡咯聚合过程和性质的影响.当自组装膜较完美时,聚吡咯沉积在自组装膜表面;而当自组装膜有一定缺陷时,吡咯在针孔处成核,然后继续生长并完全覆盖在自组装膜表面.研究结果表明,烷基硫醇的链越短,吡咯聚合越容易;疏水的烷基硫醇自组装膜有利于聚吡咯在电极表面的生长. 相似文献
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二茂铁硫醇自组装膜的电化学行为及其离子对效应 总被引:5,自引:4,他引:5
详细了研究10-二基铁-1-癸硫醇(HSC10Fc)在金基底上形成的自组装单分子膜的电化学行为,发现HSC10Fc在金基底上形成稳定的自组装膜,并且在0.1mol/L的HClO4溶液中表现出可逆的氧化还原行为,但其氧化还原峰的峰形和峰位极易溶液中阴离子种类和浓度的影响,考察了二茂铁自组装膜及通过后置换形成的二茂铁硫醇/十二烷基硫醇混合膜在混合电解液中的电化学行为,直接比较了两种不同阴离子与二茂铁阳 相似文献
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采用硫醇自组装单层膜结合悬浮纳米线技术制备了分子结器件, 对比研究了非电活性的1-十一烷基硫醇(C11)和电活性的二茂铁己硫醇(FHT)分子结的电荷传输特性. 结合两种传输机理, 提出一种新的模型拟合了分子结的电流-电压特性, 发现了氧化还原活性中心二茂铁(Ferrocene, Fc)可以使电荷传输机理由隧穿变成隧穿与跳跃共存. 结合变温实验验证了这一机理, 并对这种混合机理出现的原因进行了分析. 相似文献
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聚电解质多层有序膜电极的生成及其电化学特性 总被引:2,自引:1,他引:2
研究了在金电极表面硫醇自组装膜上聚电解质多层有序膜的形成过程及其电化学特性。用紫外光谱和电化学方法对多层有序膜进行了表征。结果表明,有序膜影响着离子在膜中的穿透性,离子型电活性物质如铁氰根离子和亚甲蓝等可嵌入有序膜中,研究了多层有序膜电极的电化学特性及膜中铁氰根离子的电化学行为。 相似文献
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金表面不同链长烷基硫醇自组装单分子膜表面电势的变化规律 总被引:1,自引:0,他引:1
从Helmholtz模型出发,对生长在金表面不同链长烷基硫醇自组装单分子膜(SAM)表面电势的变化规律进行了理论研究.利用量子化学软件Gaussian03和MOPAC,讨论了分子偶极矩、相对介电常数以及分子的倾斜角对SAM表面电势的影响.研究表明,不同链长烷基硫醇SAM中分子的倾斜角随烷基链长度的规律性变化是引起SAM表面电势变化的主要原因.从SAM形成机制出发,对金表面不同链长烷基硫醇SAM表面电势的变化规律及其成因提出了新的解释. 相似文献
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Fattakhova Rohlfing D Rathouský J Rohlfing Y Bartels O Wark M 《Langmuir : the ACS journal of surfaces and colloids》2005,21(24):11320-11329
Mesoporous silica thin films were shown to be an appropriate matrix for immobilization of discrete electroactive moieties, yielding uniform transparent thin film electrodes with defined texture and enhanced electrochemical activity. The mesoporous silica films prepared on conducting FTO-coated glass substrate were postsynthetically functionalized. Alkoxysilanes were used as precursors for subsequent grafting via ionic or covalent bonds of representative electroactive species, such as polyoxometalate PMo12O(40)3-, hexacyanoferrate(III), and ferrocene. The electrochemically active concentration within the silica-based composite electrodes achieves 90, 260, and 60 micromol cm(-3) for polyoxometalate, hexacyanoferrate(III), and ferrocene, respectively. The amount of molecules involved in the charge-transfer sequence is proportional to the film thickness and comparable to the total amount of embedded guests. Thus, eventually the whole bulk volume of the modified silica films is electrochemically accessible. Immobilization in the chemically modified silica matrix alters the redox potential of the electroactive molecules. Electron exchange between the adjacent redox centers (electron hopping) is proposed as a possible charge propagation pathway through the insulating silica matrix, which is supported by the fact that the high charge uptake is observed also for the hybrid electrodes with the covalently anchored redox guests. 相似文献
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Zhang WW Li HF Liu L Xie JL Lu CS Zhou Y Ren XM Meng QJ 《Journal of colloid and interface science》2003,261(1):82-87
A series of thiol-functionalied azobenzene derivatives (RAzoCnSH: R=H for n=3-6, abbreviated as AzoCnSH; R=CH(3)CONH for n=4, abbreviated as aaAzoC4SH) on gold electrodes were prepared and their self-assembly and electrochemical properties were studied by cyclic voltammetry. They all formed uniform and reproducible self-assembled monolayers (SAMs) on gold and showed well-behaved voltammetric responses in aqueous solution. Both the length of the alkyl chain spacer and the H-bonding of the end acetamino group had effects on the stability and the electrochemical kinetics of the SAMs, and the effect of the H-bonding was dominant. The surface coverage of the SAMs (AzoCnSH) is gradually increased with an increase of the alkyl chain spacer length, whereas the presence of the terminal acetamino group leads to a greater increase of the surface coverage. At a low scan rate, voltammetric responses corresponding to an irreversible two-electron, two-proton reduction/oxidation of the trans-azobenzene redox center were obtained in the range of +300 mV and -800 mV, which exhibited very large peak-to-peak splitting. At a high scan rate of 500 mV/s, two steps of reversible one-electron, one-proton reduction/oxidation corresponding to the cis-isomer in azobenzene-thiol SAMs (n is odd) was clearly observed between +300 and -200 mV. The apparent electron-transfer rate is decreased with increasing distance between the azobenzene redox center and the gold electrode. The existence of the end acetamino group which restricted the conformational change during the redox process also led to a decrease of the standard rate constant, and this restriction effect is more predominant than the distance effect. 相似文献
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Three ferrocenyl-alkanethiol derivatives with different functional groups linking ferrocene to an alkanethiol chain have been synthesized and characterized electrochemically in bulk solution and in self-assembled monolayer films on gold electrodes. Relative affinities of the ferrocenyl-alkanethiols and of the corresponding n-alkanethiols for the electrode surface were evaluated by the competitive self-assembly method. The affinity of the ferrocenyl-alkanethiols for the surface, relative to that of the corresponding alkanethiols, is a function of the polarity of the functional group linking ferrocene to the alkanethiol chain. In general, nonpolar linking groups (methylene) show a stronger affinity for the surface than do polar groups (carboxamides) and especially charged groups (quaternary ammonium salts). It is postulated that electrostatic effects are critically important during self-assembly. Redox potentials for the three ferrocenyl-alkanethiol derivatives scale approximately with the electron donating/withdrawing effects of the functional groups on the cyclopentadiene rings. However, redox potentials for the surface-confined molecules are consistently more positive than for the identical molecules in bulk solution. 相似文献
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Yue H Khoshtariya D Waldeck DH Grochol J Hildebrandt P Murgida DH 《The journal of physical chemistry. B》2006,110(40):19906-19913
Cytochrome c was coordinatively bound to self-assembled monolayers of pyridine-terminated alkanethiols on Au and Ag electrodes. The mechanism of heterogeneous electron transfer of the immobilized protein was investigated by cyclic voltammetry and time-resolved surface-enhanced resonance Raman spectroelectrochemistry. The temperature, distance, and overpotential dependencies of the electron transfer rates indicate a change of mechanism from a tunneling controlled reaction at long distances (thicker films) to a solvent/protein friction controlled reaction at smaller distances (thinner films). 相似文献
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Redox cycling of enzymatically amplified electroactive species has been widely employed for high signal amplification in electrochemical biosensors. However, gold (Au) electrodes are not generally suitable for redox cycling using a reducing (or oxidizing) agent because of the high background current caused by the redox reaction of the agent at highly electrocatalytic Au electrodes. Here we report a new redox cycling scheme, using nicotinamide adenine dinucleotide (NADH), which can be applied to Au electrodes. Importantly, p-aminophenol (AP) redox cycling by NADH is achieved in the absence of diaphorase enzyme. The Au electrodes are modified with a mixed self-assembled monolayer of mercaptododecanoic acid and mercaptoundecanol, and a partially ferrocenyl-tethered dendrimer layer. The self-assembled monolayer of long thiol molecules significantly decreases the background current of the modified Au electrodes, and the ferrocene modification facilitates easy oxidation of AP. The low amount of ferrocene on the Au electrodes minimizes ferrocene-mediated oxidation of NADH. In sandwich-type electrochemical immunosensors for mouse immunoglobulin G (IgG), an alkaline phosphatase label converts p-aminophenylphosphate (APP) into electroactive AP. The amplified AP is oxidized to p-quinoneimine (QI) by electrochemically generated ferrocenium ion. NADH reduces QI back to AP, which can be re-oxidized. This redox cycling enables a low detection limit for mouse IgG (1 pg mL(-1)) to be obtained. 相似文献
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Adsorption of a series of ethoxylated cationic surfactants at model surfaces of alkanethiol self-assembled monolayers was studied by the surface plasmon resonance technique. Model surfaces were tailor-made by choosing alkanethiols or mixtures of alkanethiols with methyl, hydroxyl, carboxyl, and trimethylammonium groups in terminal position. The ethoxylated and quaternized cationic surfactants having from 2 to 18 oxyethylene units, showed a decrease in adsorbed amount with increasing oxyethylene chain length for both hydrophobic and hydrophilic surfaces. On a negatively charged surface, containing carboxylate groups, the surfactant with only two oxyethylene groups adsorbed strongly due to electrostatic attraction and the adsorption increased with increasing amount of surface carboxylate groups. This work shows the usefulness of self-assembled alkanethiols on gold as a tool for performing surfactant adsorption studies on surfaces with variable hydrophobicity and charge. 相似文献
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An electroactive self-assembled monolayer was fabricated by covalent attachment of protocatechuic acid at a gold surface and its electrochemical behavior was investigated using cyclic voltammetry. The modification involves a three-step method: (i) preparation of a cysteamine self-assembled monolayer, (ii) activation of the carboxylic groups of protocatechuic acid in solution and (iii) modification of cysteamine self-assembled monolayers by activated protocatechuic acid to functionalize the self-assembled monolayer by catechol-terminated groups. This resulting thin film modified electrode was tested successfully for the electrocatalytic determination of dopamine in aqueous solution. 相似文献
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Guozhen Liu Till Bcking J. Justin Gooding 《Journal of Electroanalytical Chemistry》2007,600(2):335-344
The modification of gold electrodes with 4-carboxyphenyl diazonium salts to form stable layers for sensing applications is reported. Electrochemical reduction of 4-carboxyphenyl diazonium salts on gold electrodes yielded more stable layers than alkanethiol self-assembled monolayers in terms of extremes of electrode potential, sonication and with time. The application of the 4-carboxyphenyl modified electrodes for electrochemical sensing, which typically requires short chain alkanethiols on gold electrodes, is demonstrated via the covalent attachment of oligopeptides for the selective detection of Cu2+, Cd2+ and Pb2+. The diazonium salt/peptide modified gold electrodes not only had greater stability but also performed with lowest detected concentration to alkanethiol/peptide modified electrodes and with far greater sensitivity than the metal ion sensors when diazonium salt/peptide modified similar glassy carbon electrodes were employed. 相似文献
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Borgh A Ekeroth J Petoral RM Uvdal K Konradsson P Liedberg B 《Journal of colloid and interface science》2006,295(1):41-49
A biomimetic model system based on long-chain alkanethiols tailored with serine, threonine and tyrosine side-chain groups is created as a platform for the study of phosphorylated amino acids. The phosphorylated analogues are synthesized with protective tert-butyl groups that after assembly on thin polycrystalline gold films are removed in an acidic deprotection solution to form the corresponding phosphate self-assembled monolayers (SAMs). The SAMs are thoroughly characterized with null ellipsometry, contact angle goniometry, infrared reflection-absorption spectroscopy and X-ray photoelectron spectroscopy. The assembly and the subsequent deprotection process are optimized with respect to molecular orientation and chain conformation by varying the incubation time and the exposure time to the deprotection solution. The high quality of the generated SAMs suggests that the present assembly/deprotection approach is an attractive alternative when traditional synthetic routes become demanding because of solubility problems. 相似文献
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Wei J Liu H Dick AR Yamamoto H He Y Waldeck DH 《Journal of the American Chemical Society》2002,124(32):9591-9599
A novel strategy for the immobilization of cytochrome c on the surface of chemically modified electrodes is demonstrated and used to investigate the protein's electron-transfer kinetics. Mixed monolayer films of alkanethiols and omega-terminated alkanethiols (terminated with pyridine, imidazole, or nitrile groups that are able to ligate with the heme) are used to adsorb cytochrome c to the surface of gold electrodes. The use of mixed films, as opposed to pure films, allows the concentration of adsorbed cytochrome to remain dilute and ensures a higher degree of homogeneity in their environment. The adsorbed protein is studied using electrochemical methods and scanning tunneling microscopy. 相似文献