Aquifex aeolicus membrane hydrogenase for hydrogen biooxidation: Role of lipids and physiological partners in enzyme stability and activity

Hydrogenase I from the hyperthermophilic bacterium Aquifex aeolicus is a good candidate for biotechnological devices thanks to its ability to oxidize hydrogen at high temperature, even in the presence of oxygen and CO. In order to enhance the enzyme stability and the catalytic efficiency, we investigated the hydrogen oxidation process with hydrogenase I embedded in a physiological-like environment. Hydrogenase I partners in the metabolic chain, namely membrane quinone and cytochrome b, were purified and fully characterized. The complex hydrogenase I–cytochrome b was inserted into liposomes. Surface Plasmon Resonance revealed that quinone took part in the stabilization of the complex. By use of molecular modelization and electrochemistry analysis, enzyme stability has been demonstrated to be stronger and enzymatic efficiency to be five times higher when hydrogenase is embedded into the liposomes. This result raises the possibility of using hydrogenases as biocatalysts in fuel cells.     

One step gold (bio)functionalisation based on CS2-amine reaction

Dithiocarbamates have been regarded as alternative anchor groups to thiols on gold surfaces, and claimed to be formed in situ through the reaction between secondary amines and carbon disulphide. In this paper, we further exploit this methodology for a convenient one step biomolecule immobilisation onto gold surfaces. First, the reactivity between CS₂ and electroactive compounds containing amines, primary (dopamine), secondary (epinephrine), and an amino acid (tryptophan) has been investigated by electrochemical methods. Cyclic voltammetric characterisation of the modified electrodes confirmed the immobilisation of all the target compounds, allowing the estimation of their surface concentration. The best result was obtained with epinephrine, a secondary amine, for which a typical quasi-reversible behaviour of surface confined electroactive species could be clearly depicted. Electrochemical reductive desorption studies enabled to infer on the extent of the reaction and on the relative stability of the generated monolayers. Bio-functionalisation studies have been accomplished through the reaction of CS₂ with glucose oxidase in aqueous medium, and the catalytic activity of the immobilised enzyme was evaluated towards glucose, by electrochemical methods in the presence of a redox mediator. Scanning tunnelling microscopy (STM) and Atomic force microscopy (AFM) were used respectively, to characterize the gold electrodes and Glucose Oxidase coverage and distribution on the modified surfaces.     

采油管材N80钢在流动介质中的腐蚀行为研究

采用循环流动腐蚀试验装置，研究了N80钢在模拟油田含氧流动介质中的腐蚀行为，分析比较了温度、流速等因素的影响。结果表明，在流动的含氧模拟油田采出液中，N80钢的腐蚀速度因溶液温度不同而异，30℃时，随流速提高，腐蚀速度加快，而当温度升到40℃以后，随流速提高腐蚀速度反而下降。     

In-situ X-ray diffraction study of the initial dealloying of Cu3Au(001) and Cu0.83Pd0.17(001)

Dealloying and selective dissolution are serious corrosion processes, but also employed in technology. We studied the surface structure of Cu_0.83Pd_0.17(001) and Cu₃Au(001) during electrochemical selective Cu dissolution below the critical potential in-situ in 0.1 M H₂SO₄ (pH = 1) electrolyte. In both cases we observe the formation of an epitaxial layer of nano-scale islands of the noble component of the original alloy (Au or Pd). These islands form a metallic passivation layer suppressing massive dissolution of Cu. The Au islands developed {111} facets. By re-deposition of Cu ions from the electrolyte solution onto Pd islands, an epitaxial Cu layer is formed.     

Direct observation of the interface during sliding tribo-corrosion

A new test apparatus has been developed to allow the sliding interface between the inert and “active” surfaces during tribo-corrosion to be viewed directly. This apparatus allows the nominal contact area to be viewed and will, it is hoped, eventually allow the real contact area and the role of wear debris to be clearly revealed. Initial experiments reciprocating glass plates against AISI 316 balls in 0.1 M Na₂SO₄ have shown that the corrosion current does not linearly depend on the wear scar area and that the electrochemical contribution to the total material loss increases with increasing sliding distance.     

Molecular structure and electrochemical properties of alkyldithiocarbamates

Cyclic voltammetry, chronoamperometry, chronocoulometry and rotating disc electrode techniques have been used to study redox properties of dithiocarbamate lithium salts solutes in 0.1 M LiClO₄/DMSO solution. The investigated compounds have been synthesized from N,N′-dimethylethylenediamine to which one or two dithiocarbonyl groups were attached by a reaction with CS₂ in an alkaline solution. Voltammetric studies of the oxidation of these moieties showed the irreversible, though reproducible, broad peak at scan rates ranging from 0.01 to 0.5 V s⁻¹. The chronoamperometric and rotating disc electrode experiments confirmed the consumption of 1e/active group. Upon changing the electrode from Pt to glassy carbon only slight shift of the anodic peak potential, and negligible current change has been observed. These findings are interpreted as an indication that the electrode materials do not participate directly in the dithiocarbamate radicals formation (for example, via chemisorption) and in further dimerization of the radicals to thiuram disulfide. The latter process is assumed to proceed at the rate close to the diffusion limit. The calculated symmetry coefficient are distinctly lower than 0.5, the value predicted by the Butler-Volmer theory. Such an outcome implies that the potential range where the reaction proceeds is much more positive than the standard potential of the reaction. The oxidation of the compound containing two electroactive groups has led to the formation of a wide spectrum of diverse disulfide compounds differing one from another by the molecular weight (diffusion coefficient) owing to the various degree of the coupling.The semi-empirical quantum-chemical calculations showed the structure reorganization of the dithiocarbamate anions upon electron detachment enforced by localization of the unpaired electron on the sulfur atoms. It may favour kinetically the formation of thiuram disulfide through the fast homogeneous dimerization of the dithiocarbamate radicals.     

Investigation of fluoacid based conversion coatings on aluminum

Conversion coatings on metals enhance paint or lacquer adhesion and promote corrosion resistance. Traditionally, these conversion coatings were based on chromium chemistry. In recent years, formulations based on fluotitanic or fluozirconic acid and polymer have demonstrated performance on a par with chromium-based treatments. The choice of fluoacid and polymer in the treatment has a strong impact on coating performance. The impact of pretreatment composition was demonstrated for aluminum extrusion processes. Electrochemical investigation, including linear polarization and electrochemical impedance spectroscopy, was used to differentiate corrosion resistance among the various treatments. Scanning electron microscopy, grazing angle infrared spectroscopy, and X-ray photoelectron spectroscopy were used to elucidate chemical composition of the treated aluminum surfaces.     

WC粒度对超音速火焰喷涂WC-10Co-4Cr涂层耐腐蚀性能的影响

采用制粒?高温快速烧结法制备两种分别含亚微米级和微米级WC粒径的WC-10Co-4Cr喷涂粉末,并用超音速火焰喷涂(HVOF)技术在45#钢基体上制备涂层;利用扫描电子显微镜和电化学工作站分别对涂层的显微形貌及耐腐蚀性能进行分析检测,探讨WC粒度对涂层耐腐蚀性能的影响和涂层的电化学腐蚀机理。研究结果表明：两种涂层组织致密,界面结合良好;含亚微米级WC粒径的涂层具有相对较低的孔隙率,使其涂层的耐腐蚀性能优于含微米级WC粒径的涂层。在3.5%NaCl溶液中涂层的硬质相WC和粘结相Co发生电偶腐蚀,且低电位的Co相优先腐蚀,导致WC颗粒脱落,出现凹坑及点蚀现象。     

质子交换膜燃料电池(PEMFC)的建模方法研究

质子交换膜燃料电池（PEMFC）是21世纪最有生命力的发电技术之一。参考大量文献，总结出PEMFC建模的基本方法。从电化学、液体动力学角度出发，全面地分析三维PEMFC数学模型，其具普遍意义。并阐明遗传算法、神经模糊控制技术在PEMFC控制方面的应用。     

Size effects on mass transport and storage in lithium batteries

The contribution deals with the significance of size effects for lithium-based batteries. The relevant size effects range from purely geometrical effects to effects in which the local thermodynamics is varied. In this context, several recent findings towards improved electrolytes and electrodes are discussed.