Combination of in situ UV–Vis-NIR spectro-electrochemical and a.c. impedance measurements: A new, effective technique for studying the redox transformation of conducting electroactive materials

Simultaneous in situ UV–Vis-NIR spectro-electrochemical and a.c. impedance techniques have been realized for the first time. Combination of the data obtained by these parallel, independent methods can be exploited in the future in the elucidation of the redox mechanism of various transparent electroactive layers.     

Molecularly imprinted polymer-based electrochemical sensors for biopolymers

Electrochemical synthesis and signal generation dominate among the almost 1200 articles published annually on protein-imprinted polymers. Such polymers can be easily prepared directly on the electrode surface, and the polymer thickness can be precisely adjusted to the size of the target to enable its free exchange. In this architecture, the molecularly imprinted polymer (MIP) layer represents only one ‘separation plate’; thus, the selectivity does not reach the values of ‘bulk’ measurements. The binding of target proteins can be detected straightforwardly by their modulating effect on the diffusional permeability of a redox marker through the thin MIP films. However, this generates an ‘overall apparent’ signal, which may include nonspecific interactions in the polymer layer and at the electrode surface. Certain targets, such as enzymes or redox active proteins, enables a more specific direct quantification of their binding to MIPs by in situ determination of the enzyme activity or direct electron transfer, respectively.     

Tetrazole thiolate/disulfide organic redox couples carrying long alkyl groups in dye-sensitized solar cells with Pt-free electrodes

Colorless tetrazole thiolate/sulfide redox couples carrying long alkyl groups, such as n-butyl, n-hexyl, and n-octyl groups, were synthesized as electrolytes in iodine/iodide-free dye-sensitized solar cells (DSSCs). Among N719/TiO₂-based DSSCs employing these highly soluble redox couples for 3-methoxypropionitrile (3-MPN) and ionic liquid with PEDOT counter electrode, the DSSC with n-hexyl redox analogue gave an optimized η value of 4.32%. An observed respectable quantum efficiency for 400–500 nm light is in sharp contrast to the decreased performance for iodine/iodide systems that originates from the substantial light absorption of iodine. On the other hand, the redox possessing n-octyl group significantly lowered the cell performance, which could be a result of the much increased resistance of electrolyte diffusion in the DSSC.     

TbFeO3上CO氧化动力学

用柠檬酸络合法制备ＴｂＦｅＯ３。用ＸＲＤ测定ＴｂＦｅＯ３的钙钛矿结构。用脉冲法测定了ＴｂＦｅＯ３还原步骤的速度常数。用外缩环流动无梯度反应器研究了在ＴｂＦｅＯ３上ＣＯ氧化稳态动力学。实验结果服从Ｒｅｄｏｘ机理方程。用正交设计法估计Ｒｅｄｏｘ机理方程中的动力学参数。还原催化剂再氧化是ＴｂＦｅＯ３上ＣＯ氧化的控制步骤。     

Investigations on equilibria between Ag(I) and tetraazacyclic amines in dimethylsulfoxide

Summary The formation constants of complexes of Ag(I) with 1,4,8,11-tetraazacyclotetradecane (TACT), 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (TMTACT), and 1,4,8,12-tetraaza-cyclopentadecane (TACP) as well as equilibrium constants of the disproportionation of Ag(TACT)⁺ and Ag(TACP)⁺ in dimethylsulfoxide have been determined by spectrophotometry and potentiometry. Ag(II) complexes of the same amines have also been characterized by spectrophotometry. The mechanism of the electrode processes of the complexes under investigations has been elucidated by voltammetric and coulometric methods; formal potentials of the redox systems have been determined.

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Untersuchungen der Gleichgewichte zwischen Ag(I) und tetraazacyclischen Aminen in Dimethylsulfoxid

Zusammenfassung Die Bildungskonstanten von Komplexen zwischen Ag(I) und 1,4,8,11-Tetraazacyclotetradecan (TACT), 1,4,8,11-Tetramethyl-1,4,8,11-tetraazacyclotetradecan (TMTACT) und 1,4,8,12-Tetraazacyclopentadecan (TACP) sowie die Gleichgewichtskonstanten der Disproportionierungsreaktion von Ag(TACT)⁺ und Ag(TACP)⁺ wurden in Dimethylsulfoxid spektrophotometrisch und potentiometrisch ermittelt. Ag(II)-Komplexe derselben Amine wurden ebenfalls spektrophotometrisch charakterisiert. Der Mechanismus der Elektrodenprozesse der untersuchten Komplexe wurde mittels voltammetrischer und coulometrischer Methoden aufgeklärt; die formalen Potentiale der Redoxsysteme wurden bestimmt.

     

Graft copolymerization of butyl acrylate onto casein initiated by potassium diperiodatonickelate(IV) in alkaline medium

The novel redox system, potassium diperiodatonickelate (Ni(IV))-casein, was used to initiate graft copolymerization of butyl acrylate onto casein under heterogeneous conditions in aqueous 5% potassium hydroxide solution, which showed high grafting efficiency and percent grafting. FT i.r. spectroscopy, thermal analysis and scanning electron microscopy characterized the structures and properties of the grafted copolymer. The effects of synthesis variables in the graft copolymerization have been discussed in the light of grafting efficiency, percent grafting and the rate of polymerization. A possible initiation mechanism is proposed.     

Easily Switchable 18π-, 19π-, and 20π-Conjugation of Diazaporphyrin Double-Pincer Bispalladium Complexes

Ni^II 3,7,13,17-tetrapyridyl-5,15-diazaporphyrin serves as a double tridentate ligand to Pd^II ions to provide a pincer-type bispalladium complex. Electrochemical analysis revealed that the bispalladium complex shows excellent ability to accept electrons and reversible redox properties due to the coordination of the two cationic Pd^II centers to the meso-nitrogen atoms. We isolated and characterized one- and two-electron reduction species of the bispalladium complex. The 20π antiaromatic nature of the two-electron reduction species was confirmed by ¹H NMR spectroscopy, UV/Vis-near-IR (NIR) absorption spectra, and density functional theory (DFT) calculations. X-ray diffraction revealed highly twisted structures for the bispalladium complexes regardless of the oxidation state.     

Cholesterol levels and activity of membrane bound proteins: characterization by thermal and electrochemical methods

The long-term goal of this investigation is to study the effects of increased cholesterol levels on the molecular activity of membrane-bound enzymes such as nitric oxide synthase, that are critical in the functioning of the cardiovascular system. In this particular investigation, we used differential scanning calorimetry (DSC) and dielectric thermal analysis (DETA) to study the effect of added cholesterol on melting/recrystallization and dielectric behavior, respectively, of phosphatidylcholine (PC) bilayered thin films. We also used electrochemical methods to investigate the effect of added cholesterol on the redox behavior of the oxygenase domain of nitric oxide synthase as a probe embedded in the PC films. The results show that added cholesterol in the PC films seems to depress the molecular dynamics as indicated by lowered current responses in the presence of cholesterol as well as a slight increase of the transition temperature in the overall two-phase regime behavior observed in PC–cholesterol films. These results are rationalized in the context of the general DSC and DETA behaviors of the PC–chol films.     

SO·4-自由基氧化酪氨酸反应中的溶剂效应

研究了水-乙腈混合溶液中SO·4-自由基氧化酪氨酸的反应.实验结果表明,SO·4-自由基氧化酪氨酸的反应机制不因乙腈的加入而改变,但所产生的瞬态粒子的动力学行为受到较大影响.随介质中乙腈体积分数的增加,SO·4-的衰变速率减慢而酪氨酸中性自由基(TyrO·)的衰变速率加快.我们认为这两种自由基所呈现出来的相反的溶剂效应是由于其所带电荷的不同.随介质中乙腈体积分数的增加,SO·4-氧化酪氨酸的反应速率减慢.这一实验结果意味着,在有机溶剂存在的情况下TyrO·/TyrOH的氧化还原电势可能发生了变化,从而旁证了关于TyrO·/TyrOH的氧化还原电势因酪氨酸从游离状态变到肽或蛋白质中而发生变化的推测.