Modification of the gold electrode for the electrochemical study of cytochrome c

The modification of the gold electrode by some nitrogen hetero-cycles is used for electrochemically studying cytochrome c. Fifteen molecules are tested, but only six are active. The prominent characteristics of the active molecules are defined, and the competition between cytochrome c, 4,4′-bipyridine, 1,2-bis(4-puridyl)ethylene and aldrithiol-4 for the adsorption at the gold electrode has been studied in particular.     

Effect of cobalt bis(dicarbollides) on electrochemical oxygen reduction on Pt electrode in methanol-acid solution

Electrochemical oxygen reduction on a platinum electrode has been investigated in methanol-0.05 M H₂SO₄ aqueous solutions in the presence of acids of cobalt bis(dicarbollide) (H⁺B⁻, H⁺[(1,2-C₂B₉H₁₁)₂-3-Co]⁽⁻⁾) or its hexachlorinated derivative (H⁺BCl⁻, H⁺ [(8,8′,9,9′,12,12′-Cl₆-(1,2-C₂B₉H₈)₂-3-Co)]⁽⁻⁾). Methanol oxidation was suppressed with H⁺BCl⁻ significantly, and selective oxygen reduction was achieved on a platinum electrode. The efficiency of oxygen reduction to H₂O, which depended on the electrode potential, was lower by 2% to 20% than that without H⁺BCl⁻. The mechanism was investigated by surface-enhanced infrared absorption spectroscopy (SEIRAS). H⁺BCl⁻ suppresses formation of both the catalytic poison, linear CO (ads.), from methanol and the formate, the intermediate of the non-CO path of methanol oxidation.     

Electropolymerization of chlorinated phenols on a Pt electrode in alkaline solution. Part II: An electrochemical quartz crystal microbalance study

Electropolymerization of phenol and mono-, di-, tri-, pentachlorophenols was studied using EQCM on a Pt electrode at 0.78 V (SHE) in 1 M NaOH solution containing 0.1 M of the corresponding phenol. The highest electropolymerization rate was found for ortho-substituted chlorophenols indicating a weak fouling of the electrode. Low electropolymerization rates for para-substituted chlorophenols suggest a low permeability of the polymer film, resulting in rapid electrode fouling. The EQCM data suggest that electropolymerization of chlorophenols occurs without Cl-elimination for the monomers with unsubstituted ortho and para positions. Dechlorination is most pronounced for electropolymerization of para-substituted isomers. The mechanism of electropolymerization of chlorophenols is discussed.     

SFG study on potential-dependent structure of water at Pt electrode/electrolyte solution interface

Structure of water at Pt/electrolyte solution interface was investigated by sum frequency generation (SFG) spectroscopy. Two broad peaks were observed in OH stretching region at ca. 3200 cm⁻¹ and ca. 3400 cm⁻¹, which are known to be due to the symmetric OH stretching (υ₁) of tetrahedrally coordinated, i.e., strongly hydrogen bonded “ice-like” water, and the asymmetric OH stretching (υ₃) of water molecules in a more random arrangement, i.e., weakly hydrogen bonded “liquid-like” water, respectively. The SFG intensity strongly depended on electrode potential. Several possibilities are suggested for the potential dependence of the SFG intensity.     

铂电极上氟苯电化学降解机理及动力学

引言 氟苯(FB)广泛应用于医药、农药、染料、氟碳表面活性剂以及氟塑料等行业.FB可透过皮肤进入人体,长期或短期接触会刺激眼睛、皮肤和呼吸道,破坏肝、肾及肺、中枢神经等.     

The influence of electrochemical annealing in CO saturated solution on the catalytic activity of Pt nanoparticles

Combining non-destructive, identical location—transmission electron microscopy (IL-TEM) with rotating disk electrode (RDE) measurements, the influence of different treatment procedures on the catalytic activity of carbon supported Pt nanoparticles is probed. IL-TEM shows that the treatment of the catalyst has only minor influence on its structure or the particle shape and size; in particular no treatment induced particle agglomeration is observed. At the same time, both CO stripping and CO bulk measurements are significantly influenced by the electrochemical treatment. In consistence with previous studies this can be explained by the removal of defects in the CO adlayer structure while cycling in CO saturated solution. In contrast, however, it is demonstrated that CO annealing has no impact on the oxygen reduction reaction in the mixed kinetic-diffusion control potential region.     

Structure of detonation waves in nitromethane and a nitromethane/methanol mixture

The results of experimental studies of the structure of the reaction zone for steady-state detonation of nitromethane and its mixtures with methanol. For pure nitromethane, the characteristic reaction time and detonation parameters were determined. For a nitromethane/methanol mixture, a dependence of the detonation parameters of the mixtures on methanol concentration is presented. It is shown that in pure nitromethane and with small additions of methanol, the detonation front is stable, or the size of the inhomogeneities of the front is less than 1 m. At a methanol concentration of 10% or higher, instability of the front is observed.     

The influence of chemical passivation on the PZT/Pt electrode interface

It has been recognized that the interdiffusion of atomic species between a PZT film and the Pt bottom electrode leads to the gradual degradation of a PZT capacitor. In order to prevent this interdiffusion, experimental studies on chemical passivation to the bottom electrode surface were carried out by the sulfurization method. It was observed that a sulfur layer was built up on the Pt substrate with small grains, which resulted in a structural change at the Pt surface. Atomic force microscopy (AFM) showed that the film roughness of the Pt surface was increased by sulfur treatment. Pb(Zr_0.5Ti_0.5)O₃(PZT) thin films were prepared on a Pt/Ti/SiO₂Si bottom electrode by spin-coating techniques. The microstructure and the preferred orientation of the PZT films were shown to depend on the sulfur-treated electrode. The PZT capacitor on a clean Pt electrode was confirmed to be ferroelectric with Pr=17.7 μC/cm² and Ec=65 kV/cm from the P-E hysteresis curves. The fatigue behavior of a PZT film capacitor prepared on a sulfur-treated one was observed to be relaxed, but the absolute value of Pr was paid off.     

The electrochemical behavior of erythromycin A on a gold electrode

The reactivity of erythromycin (pure) was investigated on a gold electrode in neutral electrolyte by cyclic voltammetry. The resulting structural changes were observed with HPLC and FTIR spectroscopy by analyzing the bulk electrolyte after the electrochemical reactions. The results were compared with those previously obtained for azithromycin and clarithromycin under the same experimental conditions. It was found that the electrochemical behavior of erythromycin A differs from that of azithromycin dihydrate. Comparison with the electrochemical activity of basic clarithromycin suggests that the electrochemical activity of erythromycin is similar but more pronounced than that of clarithromycin.HPLC analysis confirmed these observations and showed that during the electrochemical oxidation of erythromycin A, the amount of starting macrolide decreased while the amount of starting impurities increased. Also some new products were observed. FTIR spectroscopy confirmed that erythromycin A is more reactive than clarithromycin, although similar changes in their molecular structures were observed.     

Unfolding of cytochrome c immobilized on self-assembled monolayers. An electrochemical study

The electron transfer (ET) process of progressively unfolded bovine cytochrome c immobilized on different self-assembled monolayers (SAMs) was investigated. Insight is gained on the role of the SAM surface on the functionality of the partially unfolded and non-native forms of the adsorbed protein. Direct electrochemical measurements were performed on cytochrome c adsorbed on mercaptopyridine (MP) and mixed 11-mercapto-1-undecanoic acid/11-mercapto-1-undecanol (MUA/MU) at varying temperature, in the presence of urea as unfolding agent. Under strongly unfolding conditions, a non-native form of cytochrome c, in which the methionine ligand is replaced by a histidine, was observed on both MP and MUA/MU SAMs. The E°′ of the native form, in which the haem is axially coordinated by methionine and histidine, slightly shifts to negative values upon increasing urea concentration. However, the non-native bis-histidinate species shows a much lower E°′ value (by approximately 0.4 V) which is by far enthalpic in origin and largely determined by axial ligand swapping. Analysis of the reduction enthalpies and entropies and of the ET rate constants indicate that the nature of the SAM (hydrophilic or anionic) results in changes in the conformational rearrangement of the cytochrome c under unfolding conditions.     

Role of chloronium complex in the electrochemical chlorination of c-hexene in nitromethane

The anodic chlorination of c-hexene in NM solution having 150 ppm water content involves three charge-transfer reactions. The effect of potential on change in product distribution is more effective at the beginning of electrolysis. A mechanism for the process is suggested.     

Regioselective bromination of toluene by electrochemical method

A simple, regioselective, environmentally cleaner and economical method for the electrochemical preparation of benzyl bromide from toluene by two-phase electrolysis is reported. Electrochemical bromination of toluene is carried out in an undivided cell at 0 °C and the process parameters are studied and optimized. In this method 94% yield and 98% conversion is achieved.     

Electropolymerization of chlorinated phenols on a Pt electrode in alkaline solution Part I: A cyclic voltammetry study

Cyclic voltammetry studies were carried out on a platinum electrode in alkaline 1 M NaOH solutions containing 0.1 M of phenol, monochlorophenols, dichlorophenols, trichlorophenols and pentachlorophenol in order to compare their electropolymerization ability and the degree of deactivation of the electrode. These show that fouling of the Pt electrode occurs during the electrooxidation of all the phenols studied. Almost full deactivation of the electrode occurs in the case of phenol and 3-chlorophenol after five cycles, while 4-chlorophenol, 3,4-dichlorophenol, 2,4-dichlorophenol and 2,4,5-trichlorophenol deactivate the electrode completely after the first cycle. Partial deactivation of the electrode occurs in the case of 2-chlorophenol, 2,3-dichlorophenol, 2,6-dichlorophenol, 2,5-dichlorophenol and 2,4,6-trichlorophenol. A weak fouling of the electrode occurs in the case of 3,5-dichlorophenol, 2,3,6-trichlorophenol and pentachlorophenol. Such differences in the degree of electrode deactivation may be explained by the different structure (permeability) of the polymeric tars formed. The structure of the tars depends on the monomer structure. Presumably, more regular and dense polymer structures deactivate the electrode more rapidly. More branched, irregular high molecular weight substances deactivate the electrode more slowly.     

The electrochemical characteristics of a polydithienothiophene electrode in lithium cells

Electrosynthesized polydithieno(3,2-b:2′,3′-d)thiophene (pDTT) is a very attractive polymer electrode for battery applications. In fact this polymer has a very high doping level to which corresponds a specific capacity of 54 Ah kg⁻¹, a high coulombic efficiency and an excellent cyclability. However, these extraordinary properties are somewhat contrasted by a relatively fast self discharge of the doped pDTT electrodes. This effect has been associated to a spontaneous undoping process of the polymer electrode.     

载Pt石墨烯中空微球催化剂的制备及其电催化性能

目前,直接甲醇燃料电池（DMFC）已成为世界各国探寻新型绿色动力源的首选。铂基催化剂虽然被公认为催化甲醇氧化最有效的催化剂,但离其商业化应用仍然存在较大差距。提高铂的利用率和电催化性能被公认为是解决DMFC商业化的关键问题。基于以上考虑,本文采用一种不需要使用表面活性剂的模板辅助法成功合成出了石墨烯中空球,并利用电沉积法负载Pt纳米颗粒。该载Pt石墨烯中空微球具有非常高的比表面积（226.4m2/g）和相互连通的结构。电化学测试结果表明,该载Pt石墨烯中空球的电化学活性表面积高达43.27m2/(g,Pt),峰值电流密度几乎是商业铂碳的两倍,且稳定性明显高于商业化铂碳。该载Pt石墨烯中空球对甲醇氧化展现出了极好的应用前景。     

镉试剂在汞电极上的伏安行为

通过固液相模板反应合成了2,36,71114,15-四苯并-1,4,9,12-四氮[16]轮烯稀土金属配合物,通过测定红外、紫外-可见、核磁、元素分析及摩尔电导等数据,确定了配合物的组成及结构。     

An electrochemical methanol sensor based on a Pd-Ni/SiNWs catalytic electrode

A novel electrochemical methanol sensor based on a catalytic electrode of palladium-nickel/silicon nanowires (Pd-Ni/SiNWs) is presented in this paper. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and electrochemical methods are employed to investigate the Pd-Ni/SiNWs electrode materials. These nanocomposite materials exhibit a highly ordered, wire-like structure with a wire length of ∼50 μm and a wire diameter ranging from 100 to 300 nm. The substrate has good electrocatalytic activity towards the oxidation of methanol in alkaline solutions. The performances of the prototype sensor are characterized by cyclic voltammetry and fixed potential amperometry techniques. In a 1 mol L⁻¹ KOH solution containing different methanol concentrations, the sensor exhibits a good sensitivity of 1.96 mA mmol⁻¹ L cm⁻² with R² = 0.99 and the corresponding detection limit of 18 μmol L⁻¹ (signal-to-noise ratio = 3, S/N = 3) for cyclic voltammetry. Meanwhile, the electrode also displays a sensitivity of 0.48 mA mmol⁻¹ L cm⁻² with R² = 0.98 and the corresponding detection limit of 25 μmol L⁻¹ (S/N = 3) for a fixed potential amperometry at −0.3 V versus an Ag/AgCl reference electrode. The results demonstrate that the Pd-Ni/SiNWs catalytic electrode has potential as an efficient and integrated sensor for methanol detection.     

镉试剂在汞电极上的伏安行为

三氮烯试剂是一类性能优良的金属显色剂,镉试剂是最早应用于分析目的和研究报道的三氮烯试剂[1],镉试剂化学结构式如下： 在光度方面镉试剂有着广泛的应用,可用于检测Cd2+、Hg2+、pd2+、Cu2+、Ag+、Au3+及CN-、S2-等离子[2,3],但在电化学分析方面的应用还未见报道。     

Influence of water content on the product distribution in the electrochemical chlorination of c-hexene in nitromethane

Effect of water content on product distribution in electrochemical chlorination of c-hexene in nitromethane solution was studied. Formation of 1-chloro, c-hexanone which occurs at the beginning of electrolysis is more effective at lower water content.