Layer-by-layer assembly of multilayer films composed of avidin and biotin-labeled antibody for immunosensing

Protein multilayers composed of avidin and biotin-labeled antibody (bio-Ab) were prepared on gold surface by layer-by-layer assembly technology using the high specific binding constant (K-a: approximate to 10(15) M-1) between avidin and biotin. The assembly process of the multilayer films was monitored by using real-time BIA technique based on surface plasmon resonance (SPR). The multilayer films were also characterized by electrochemical impedance spectroscopy (EIS) and reflection absorption Fourier transform infrared spectroscopy (FTIR). The results indicate that the growth of the multilayer is uniform. From response of SPR for each layer, the stoichiometry S for the interaction between avidin and bio-Ab is calculated to be 0.37 in the multilayer whereas 0.82 in the first layer. The protein mass concentration for each layer was also obtained. The schematic figure for the multilayer assembly was proposed according to the layer mass, concentration and S value. The utility of the mutilayer films for immunosensing has been investigated via their subsequent interaction with hIgG. The binding ability of the multilayer increased for one to three layers of antibody, and then reach saturation after the fourth layer. These layer-by-layer constructed antibody multilayers enhance the binding ability than covalently immobilized monolayer antibody. This technology can be also used for construction of other thin films for immunosensing and biosensor.

Chitosan mediated assembly of gold nanoparticles multilayer

We initiate a systematic exploration of a natural polymer, chitosan, as a structural material for designing functional layers on electrode surfaces in this work. Au colloid films are organized on chitosan layer by adsorption. We have successfully constructed a multilayer An nanoparticle assembly through electrostatic interactions on chitosan functionalized quartz substrates by the alternate treatment of the substrate with solution of citrate-stabilized gold nanoparticles (negatively charged) and chitosan solution (positively charged). The resulting substrates were characterized by UV-Vis spectrometry, atomic force microscopy (AFM), and electrochemical impedance spectroscopy (EIS) measurements. These assemblies of colloid An multilayer are highly stable, and can be kept for a long time in distilled water, only being removed by scratching or extreme electrochemical conditions.

Assembly of alternating polycation and DNA multilayer films by electrostatic layer-by-layer adsorption

The assembly of alternating DNA and positively charged poly(dimethyldiallylammonium chloride) (PDDA) multilayer films by electrostatic layer-by-layer adsorption has been studied. The real-time surface plasmon resonance (BIAcore) technique was used to characterize and monitor the formation of multilayer films in solution in real time continuously. Electrochemical impedance spectroscopy (EIS) and UV-vis absorbance measurements were also used to study the film assembly, and linear film growth was observed. All the results indicate that the uniform multilayer can be obtained on the poly(ethylenimine)- (PEI-) coated substrate surface. The kinetics of the adsorption of DNA on PDDA surface was also studied by the real-time BIAcore technique; the observed rate constant was calculated using a Langmuir model (k(obs) = (1.28 +/- 0.08) x 10(-2) s(-1).

Fabrication of layer-by-layer deposited multilayer films containing DNA and its interaction with methyl green

Multilayer films were fabricated by layer-by-layer electrostatic deposition techniques between poly(diallyIdimethylammonium chloride) (PDDA) and calf thymus DNA (CT DNA) on glassy carbon and quartz substrates. Electrochemical impedance spectroscopy (EIS), Fourier transform infrared (FTIR) spectroscopy and UV-vis spectroscopy demonstrated the uniform assembly of PDDA/DNA multilayer films, and X-ray photoelectron spectroscopy confirmed the elemental composition of the films. Moreover, the interaction of DNA in PDDA/DNA films with methyl green was investigated by UV-vis spectroscopy and circular dichroism (CD). (C) 2001 Elsevier Science B.V. All rights reserved.

添加钛镁元素对热浸镀锌层性能的影响

热浸镀锌及其合金在世界各国已得到广泛的应用。为提高镀锌层性能，往镀浴中添加各种微量元素已经有了许多研究。但是对于在高纯锌中添加微量元素，排除由于锌浴不纯而导致的性能差异，报道很少。 本文选择高纯锌，在排除其它元素干扰的情况下，制备了添加钛、镁元素的热浸镀锌合金镀层，考察了分别添加钛、镁元素及同时添加钛镁元素后镀层在海水环境中的腐蚀行为及其耐蚀性能。 由于钛熔点（1668℃）远高于锌熔点（419.5℃），镁在高温下极易氧化，因而制备中间合金。在分别用分光光度法和原子吸收法测定准确含量后，按计算量进行添加。热浸镀层最外层和镀液合金成分基本一致，镀液合金性能可以反映镀层性能，制备锌钛、锌镁合金电极，进行电化学性能测试，发现添加钛、镁元素能够提高合金在海水中的耐腐蚀性能。 采用烘干溶剂法进行热浸镀，选择合适的工艺条件，助镀剂为ZnCl2、NH4Cl的混合溶液，温度460℃，镀液为添加不同含量钛镁的锌液。对所得镀层进行表观质量检测，镀层质量合格，其中添加钛元素后镀层亮度增加。镀层厚度是考察镀层性能的重要指标，通过测量发现镀层比较均匀，添加钛元素后镀层厚度减薄，添加镁元素后镀层厚度稍有增加，同时添加钛镁元素，镀层厚度稍高于单独添加钛元素，但比纯锌镀层要薄许多。添加微量钛镁后，镀层阻抗谱图和极化曲线图形状都没有大的改变，EIS等效电路拟合结果表明添加钛镁元素后镀层极化电阻增加，镀层在海水中耐蚀性能有所提高。 为进一步检测镀层的耐蚀性能，进行了中性盐雾试验，添加钛镁元素后镀层腐蚀失重减少，腐蚀失重率降低，耐盐雾腐蚀性能提高；室内模拟全浸实验所的结果与盐雾试验具有一致性，镀层刚开始时腐蚀较快随后比较稳定。

低碳钢在海底沉积物中的腐蚀行为

海底沉积物环境下钢铁的腐蚀和防护问题由于人们对海洋的广泛的开发和利用而逐渐引起人们的注意。本文对钢在海底沉积物中的腐蚀行为进行了模拟海底沉积物环境下的失重实验和电化学测量，以探讨海底沉积物环境下的钢的腐蚀行为和作用机制。失重法埋片实验表明，在没有微生物影响的海底沉积物中，钢的腐蚀速度与海洋腐蚀环境的其它区带相比是较低的。A3钢在砂型海底沉积物中的腐蚀速度约是其在粘土型海底沉积物中腐蚀速度的2倍。另外，主要用电化学方法研究了A3钢在海底沉积物中的腐蚀行为，包括线性极化阻力测量，弱极化区的动电位扫描测量和电化学交流阻抗谱（EIS）测量，计算了A3钢在海底沉积物中腐蚀的有关电化学参数，探讨了A3钢在两种类型海底沉积物中的腐蚀行为差异。认为A3钢在砂型和粘土型海底沉积物中腐蚀速度大小的差别主要是由于作为阴极去极化剂的氧在不同类型海底沉积物中的扩散速度不同。通过弱极化数据拟合和IES测量的结果表明，A3钢在海底沉积物中的腐蚀机制主要是受阴极去极化剂的氧扩散控制作用。并提出了初期腐蚀过程的等效电路和腐蚀模式图。本文较系统的研究了A3钢在海底沉积物中的电化学腐蚀行为，并首次将弱极化曲线拟合技术应用于海底沉积物腐蚀研究，得到了一些有意义的结果。结合A3钢在不同类型海底沉积物中的阻抗谱特征，提出了相应的等效电路和腐蚀模型。

硫酸盐还原菌和极化电位对海洋结构用钢在海泥中应力腐蚀开裂敏感性的影响

海洋设施长期处于恶劣的腐蚀环境中，如不加以防护，一旦发生应力腐蚀开裂（SCC），损失就会极为惨重。海底泥土区环境十分重要，因为管线和平台桩腿等都埋在海底泥中。海底泥中硫酸盐还原菌（SRB）十分活跃，而且为了防止腐蚀，海泥中的设施无一例外地采取了阴极保护，相当于设施处在长期稳定的充氢状态。因此非常有必要研究海泥中的活性SRB和极化电位对海洋结构用钢在海泥中的氢渗透行为和SCC敏感性造成的影响，弄清SCC发生和发展的过程以便采取相应的措施减缓或防止SCC。 本文通过慢应变速率拉伸实验（SSRT）、电化学阻抗谱（EIS）技术、动电位扫描极化曲线测定实验和氢渗透实验等研究了海泥中SRB和极化电位对16Mn钢和管线钢X56（API X56）的SCC敏感性造成的影响。 从渤海海泥中富集得到SRB菌种，并做出了SRB在海泥中的生长曲线；在荧光显微镜下观察SRB为弧状，可以归为脱硫弧菌属，为革兰氏阴性菌；海泥中活性SRB数量与硫电位等主要腐蚀环境因子具有一定的对应关系。 SSRT结果表明，施加阴极极化电位可以使试样断裂脆性特征明显，SCC敏感性增大；海泥中活性SRB浓度越高，断裂脆性特征越明显，SCC敏感性越大。在含SRB海泥中或阴极极化电位条件下，两种钢都容易发生SCC，氢脆（HIC）起主要作用。 随着浸泡天数的增加，试样在灭菌海泥中的Rp一直增大；在含SRB海泥中Rp先增大，又变小，并呈现出显著的Warburg阻抗特征；在灭菌海泥中，两种试样在阳极电位范围内无SCC敏感区，而在阴极电位范围内有明显的SCC敏感区；在含SRB海泥中，在阳极电位范围和阴极电位范围内均有SCC敏感区；SRB代谢产物既有阳极去极化作用，又有阴极去极化作用，能使腐蚀电流密度增加。 活性SRB的存在能够促进试样在海泥中的氢渗透；在实海工程应用中，两种钢在含SRB海泥中的氢渗透电流密度大约是在不含SRB海泥中的3~4倍。阴极极化电位能够促进试样在灭菌海泥中的氢渗透。在含SRB海泥中对试样施加阴极极化电位，氢渗透电流密度大于不加阴极极化电位时的氢渗透电流密度，也大于在不含SRB的海泥中的氢渗透电流密度。

硫酸盐还原菌对海洋用钢腐蚀行为的影响及其控制

本文研究了海水和海泥环境中硫酸盐还原菌（SRB）对海洋用钢腐蚀行为的影响及控制，探讨了SRB影响下的腐蚀机制，腐蚀产物的形成及转化过程，并研究了含有SRB的海泥环境中阴极保护对钢腐蚀的影响。 从我国青岛胶州湾海底泥中富集培养出SRB，进行分子生物学分析确定了研究菌种为肠状菌属，并以荧光显微镜和透射电镜（TEM）观察了SRB的形貌特征。 以失重法、电偶腐蚀、交流阻抗（EIS）、电子探针（EPMA）、TEM等手段研究了海洋用钢在含有活性SRB的海泥和海水环境中，从最初的细菌附着到代谢产物导致腐蚀产物从氧化物到硫化物的转化，腐蚀产物的形貌及成分确定，对腐蚀由抑制到加速的过程。此外从钢基体与腐蚀产物界面角度对SRB点蚀的形成和扩展，以及单晶氧化铁立方体在SRB菌液中的生物矿化进行了探讨。 对埋在含有SRB海泥中的低碳钢的阴极保护的可靠性进行评价，重点研究活性细菌存在下不同阴极保护电位下的交流阻抗行为，并结合失重法测试不同电位下的腐蚀速度、MPN法细菌计数以得出保护电位、腐蚀速度以及细菌活性之间的关系。为达到有效的保护，-950mV (CSE)甚至更低的保护电位是需要的。较高保护电位下，细菌的生长活性与稳定性低于低电位。

铜管不锈钢管腐蚀性能及铁牺牲阳极保护研究

铜管一直是电厂凝汽器的主要应用管材，但由于其抗冲刷和抵御污染物腐蚀的能力差，特别不耐氨蚀，美国和欧洲大量使用不锈钢管替代铜管作为冷凝管，然而不锈钢管在我国的运用仅处于初步阶段。 常使用锌、铝阳极对铜管进行牺牲阳极保护，然而存在着电位差过大、阳极溶解过快的问题。铁基牺牲阳极与铜电位差适当、来源广泛、价格便宜，在一些工程上有所应用，但是目前针对铁基牺牲阳极的理论研究报道很少。 本文选用紫铜管、304不锈钢管作为实验用管材，首先运用实验室全浸实验、极化曲线和电化学阻抗研究了二者在海水和淡水中的腐蚀性能以及CO2、溶解氧对其腐蚀的影响。结果表明：CO2会加速二者的腐蚀，溶解氧却对它们的腐蚀影响不同，促进铜管的腐蚀却抑制不锈钢管的腐蚀；随浸泡时间的延长，紫铜管由于表面产物膜的生成耐蚀性提高，304不锈钢管的耐蚀性却降低；淡水中，304不锈钢管和紫铜管都具有很好的耐蚀性能。随后，运用失重法和极化曲线对比研究了紫铜管、304不锈钢管的氨蚀性能，运用SEM分析和电化学阻抗研究了紫铜在不同浓度氨溶液中的腐蚀机理。发现，304不锈钢管的耐氨蚀能力远远好于铜管；溶解氧是影响氨蚀的关键因素，其对二者氨蚀的影响也不同；紫铜管在低氨浓度和高氨浓度溶液中腐蚀机理和产物不同，低氨浓度时形成保护性的产物膜（CuO 和Cu(OH)2），高氨浓度时由活化溶解控制，生成可溶的[Cu (NH3)4]2+。 选用工业纯铁、35钢为牺牲阳极材料。恒电流实验结果表明它们具有良好的牺牲阳极性能；通过极化曲线和自腐蚀电位测试分析，认为将二者用于铜管牺牲阳极保护是可行的；实验室阴极保护效果测试表明，工业纯铁和35钢对紫铜管具有良好的保护效果，保护度达90%以上。

喷涂锌铝覆盖层在海洋环境中的腐蚀行为及失效机理

虽然采用喷涂锌铝覆盖层技术对陆上钢铁构件进行长效防护在国内外已普遍应用，但由于海洋环境的复杂和苟刻使这项技术在海上的应用受到了很大的限制。目前对于喷涂锌铝覆盖层防腐规律和机理的研究仅是从腐蚀挂片试验数据的对比，或从电位-时间图、电化学理论角度进行分析。对喷涂锌铝再涂装有机涂层的复合覆盖层的防腐规律和机理的研究则是少见报导，本论文的工作将初步揭示在该领域金属及有机复合覆盖层在海洋环境中的腐蚀过程及失效机理，为该技术在我国的发展提供理论基础。本文首先采用热喷涂工艺制备了锌、铝及其锌铝复合涂层，并对部分试样涂刷氯化橡胶面漆进行封闭处理。然后通用外海现场挂片、室内盐雾加速实验等经典腐蚀试验方法测定了不同涂层体系在不同腐蚀环境下的电位、厚度、复量随暴露时间的变化：并观察了其腐蚀失效过程中的形貌变化。通过电化学交流阻抗谱（EIS）的测试对涂层的电化学特性及腐蚀失效机理进行了分析。利用扫描电镜（SEM）、透射电镜（SEM）、电子探针（EMPA）、X-射线衍射仪（XRD）、光学金相等分析了原始状态和不同腐蚀条件下涂层表面和截面的特征、成分分布及组织结构。综合上述几种实验手段所得结果得到了以下主要结论：1. 海洋环境下，锌铝复合涂层既利用了锌涂层与钢铁基体结合好和电化学活性高的优点，又利用了铝涂层耐蚀性好和阻隔能力的长处，是一种优秀的防腐涂层方案。2. 对于封闭涂层体系，金属涂层与有机涂层的相容性十分重要，有机层的种类不同，与金属涂层复合后表现出的耐蚀能力也不一样。对于相容涂层的组合，其防护寿将大于两种涂层单独使用时防护寿命代数和，符合Ing. J. F. H的试验公式；对于非相容涂层组合，其防护寿命大大降低。3. 铝涂层的腐蚀主要是缝隙性腐蚀，锌涂层的腐蚀主要是溶脱性腐蚀。4. 锌铝复合涂层体系中作为外涂层的铝涂层应厚于内层的锌涂层的锌涂层，这样才能发挥铝涂层的“自堵塞效应”提高整个涂层体系的综合寿命。5. 由于喷涂工艺本身的特点决定了涂层具有多孔性和渗透性。金属涂层与有机层复合后极化程度增大，腐蚀速度降低。6. 金属与有机复合层的腐蚀破坏主要是由有机层与金属涂层的局部腐蚀引起的。海水从表面有机层的针孔和裂缝进入，到达金属涂层与有机层的交界处，与金属涂层发生腐蚀反应，腐蚀产物增加到一定数量后，形成鼓泡。鼓泡的出现会加速其下面金属涂层腐蚀。

Adsorption and Corrosion Inhibition Behavior of Mild Steel by One Derivative of Benzoic-Triazole in Acidic Solution

A newly synthesized benzoic-triazole derivative 3,5-dimethylbenzoic acid [1,2,4]triazol-l-ylmethyl ester (DBT) was investigated as a corrosion inhibitor of mild steel in 1 M HCl solution using weight loss measurements, potentiodynamic polarization, SEM, and EIS methods. The results revealed that DBT was an excellent inhibitor, and the inhibition efficiencies obtained from weight loss and electrochemical experiments were in good agreement. Using the potentiodynamic polarization technique, the inhibitor was proved to have a mixed-type character for mild steel by suppressing both anodic and cathodic reactions on the metal surface. The number of water molecules (X) replaced by a molecule of organic adsorbate was determined from the Flory-Huggins, Dhar-Flory-Huggins, and Bockris-Swinkels substitutional adsorption isotherms applied to the data obtained from the gravimetric experiments performed on a mild steel specimen in 1 M HCl solution at 298 K.

Electrochemical impedance spectroscopy analysis for oxygen reduction reaction in 3.5% NaCl solution

The electrochemical impedance spectroscopy (EIS) at different potentials has been used to study the oxygen reduction reaction (ORR) in 3.5% NaCl solution on glassy carbon (GC) electrode in this work. Results show that ORR consists of three two-electron reaction steps and both superoxide ion (O-2(-)) and hydrogen peroxide (H2O2), which are produced by ORR, obstruct the diffusion of oxygen to the surface of the electrode and make the EIS results change into a transmissive finite diffusion process with the real part contraction and a reflective finite diffusion process from a semi-infinite diffusion process. The values of electron transfer resistance (R-t) and diffusion resistance (R-d) were calculated from EIS. O-2(-) influenced strongly on the Rt values and induced a maximum at -0.45 V.

Corrosion inhibition of mild steel in acidic solution by some oxo-triazole derivatives

The oxo-triazole derivative (DTP) was synthesized and its inhibiting action on the corrosion of mild steel in sulphuric acid was investigated by means of weight loss, potentiodynamic polarization, EIS and SEM. The results revealed that DTP was an excellent inhibitor and the inhibition efficiencies obtained from weight loss experiment and electrochemical experiment were in good agreement. Potentiodynamic polarization studies clearly revealed that DTP acted essentially as the mixed-type inhibitor. Thermodynamic and kinetic parameters were obtained from weight loss of the different experimental temperatures, which suggested that at different temperatures (298-333 K) the adsorption of DTP on metal surface obeyed Langmuir adsorption isotherm model. (C) 2009 Elsevier Ltd. All rights reserved.

Monitoring microbial populations of sulfate-reducing bacteria using an impedimetric immunosensor based on agglutination assay

An impedimetric immunosensor was fabricated for rapid and non-labeled detection of sulfate-reducing bacteria, Desulforibrio caledoiensis (SRB) by immobilizing lectin-Concanavalin A using an agglutination assay. The immobilization of lectin was conducted using amine coupling on the surface of a gold (Au) electrode assembled with 11-Mercaptounclecanoic acid. Electrochemical impedance spectroscopy (EIS) was used to verify the stepwise assembly of the sensor system. The work conditions of the impedimetric immunosensor, such as pH of the buffer solutions and the incubation time of lectin, were optimized. Faradic impedance spectra for charge transfer for the redox probe Fe(CN)(6)(3-/4-) were measured to determine SRB concentrations. The diameter of the Nyquist diagram that is equal to the charge-transfer resistance (RI) increased with increasing SRB concentration. A linear relationship between R-ct and SRB concentration was obtained in SRB concentration range of 1.8 to 1.8 x 10(7) cfu/ml. The variation of the SRB population during the growth process was also monitored using the impedimetric immunosensor. This approach has great potential for simple, low-cost. and time-saving monitoring of microbial populations. (C) 2009 Elsevier B.V. All rights reserved.

The effect of some triazole derivatives as inhibitors for the corrosion of mild steel in 1 M hydrochloric acid

Corrosion inhibition by some new triazole derivatives on mild steel in 1 M hydrochloric acid solutions has been investigated by weight loss test, electrochemical measurement, scanning electronic microscope analysis and quantum chemical calculations. The results indicate that these compounds act as mixed-type inhibitors retarding the anodic and cathodic corrosion reactions and do not change the mechanism of either hydrogen evolution reaction or mild steel dissolution. The studied compounds following the Langmuir adsorption isotherm, and the thermodynamic parameters were determined and discussed. The effect of molecular structure on the inhibition efficiency has been investigated by ab initio quantum chemical calculations. The electronic properties such as highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) energy levels, energy gap (LUMO-HOMO), dipole moment and molecular orbital densities were calculated. (C) 2009 Published by Elsevier B.V.