离子液体中间硝基苯酚在玻碳电极上的电化学还原行为研究

在[EMIM]Br体系中,以玻碳为工作电极,铂丝为辅助电极,饱和甘汞电极为参比电极,研究了间硝基苯酚的电化学行为.采用循环伏安法和计时电量法,研究了扫描速度、温度和底物浓度等因素对其电化学行为的影响,求得扩散系数D为9.184×10^-7cm²/s,传递系数α为0.37,证明了在[EMIM]Br体系中,此反应是受扩散控制的不可逆反应.     

维生素K3电化学反应机理的紫外光谱电化学研究

用薄层池循环伏安法和现场薄层池紫外光谱电化学法研究了维生素Ｋ３（ＶＫ３）在铂电极上的电化学反应机理。薄层池循环伏安实验结果表明：ＶＫ３的电化学反应为二步１ｅ准可逆过程，现场薄层池紫外光谱电化学的实验结果和Ｎｅｒｎｓｔ图解分析表明：电解还原反应的最后产物为２－甲基－１，４－萘酚。该反应偶合有前行化学反应；还原产物经电解氧化的产物为２－甲基－１，４－萘酚。该反应偶合有前行化学反应；还原产物经电解氧化的     

2，3—二氨基吩嗪的薄层光谱电化学研究

研究了2，3—二氨基吩嗪(DAP)在金圆盘电极、金超微电极上的循环伏安行为 和在金网栅电极上的薄层循环伏安行为．在pH2．0的B—R缓冲溶液中的2，3—二氨 基吩嗪在金圆盘电极上为准可逆氧还过程；以超微电极法求得了2，3—二氨基吩嗪 在pH2．0的B—R缓冲溶液中的扩散系数，由耗竭性库仑电解和循环伏安法求得其电 极反应电子转移数和H+反应级数均为2，实验说明参与电极反应的H+也为2，并用循 环伏安法求得其标准电极反应速率常数．采用紫外—可见薄层光谱电化学方法测得 2，3—二氨基吩嗪的克式量电位和电子转移数，与电化学实验结果一致；双电位阶 跃—计时吸收紫外—可见薄层光谱电化学实验说明，2，3—二氨基吩嗪电还原无随 后化学反应，其在电极上经历了H+eH+e的两步一电子过程，生成产物2，3—二氨基 -5，10-二氢吩嗪．     

高温红外光谱电化学薄层池的制作与表征

为了拓宽光谱电化学研究范围,开展高温下电化学反应过程,本文研制了一种高温红外光谱电化学薄层池(HTC)。 研制的HTC清洗方便,操作简单,适用于水体系和有机体系。 该HTC可在室温至373 K(根据溶剂沸点,控温精度为±0.5 K)温度范围内使用,具有良好的电化学性能,红外光谱采集谱图清晰信噪比好。 利用铁氰化钾水溶液和对苯醌离子液体溶液的红外光谱电化学行为对HTC进行了表征,得到较满意的结果。     

铜(Ⅱ)邻菲咯啉蛋氨酸配合物与DNA相互作用的研究

在pH=6．86磷酸盐缓冲溶液中，采用电化学(循环伏安法、微分脉冲伏安法和 交流阻抗及数据拟合技术)、粘度测定、电子吸收光谱和溴化乙锭(EB)荧光分析法 研究了[Cu(phen)(H2O)(L—Met)]^+(phen＝1，10-邻菲咯琳，L—Met=L-蛋氨酸)与 小牛胸腺DNA的相互作用。结果发现中心铜离子在循环伏安图上呈现1对明显的准可 逆氧化还原波。当加入一定量的DNA时，配合物的氧化还原峰电流明显降低，扩散 系数减小，电化学反应电阻增大，电子光谱的最大吸收峰明显红移，产生明显的减 色效应，同时，配合物也能较大程度地猝灭EB-DNA体系的荧光，说明[Cu(phen) (H2O)(L—Met)]^+与DNA的作用较强，作用模式为部分插入作用。     

Electrochemical liquid-membrane micro-extraction of bromide into an ethyl benzoate membrane supported on a graphite-epoxy composite electrode by cyclic voltammetry

Electrochemical liquid-membrane micro-extraction is a new sample preparation strategy, which combines liquid-membrane extraction with electrochemical detection. The introduction of electrochemistry can be used to control the redox states of analytes and thereby manipulate the extraction process. The bromide in aqueous solution was electrochemically oxidized to bromine and extracted into a liquid membrane composed of ethyl benzoate supported on a graphite-epoxy composite electrode with induction of iodide redox reactions. The technique enables concentrations as low as 1 nM of bromide to be determined by cyclic voltammetry by measuring the reduction current of extracted bromine. The reduction peak current is proportional to the logarithm of bromide concentration in the range from 1 nM to 10 μM under the optimal conditions. The extraction method offers a powerful way for the electrochemical detection of trace bromide.     

Spectroelectrochemistry of EuCl3 in Four Molten Salt Eutectics; 3 LiCl−NaCl, 3 LiCl−2 KCl,LiCl−RbCl,and 3 LiCl−2 CsCl; at 873 K

Key electrochemical properties affecting pyroprocessing of nuclear fuel were examined in four eutectic melts using Eu^3+/2+ as a representative probe. We report the electrochemical and spectroelectrochemical behavior of EuCl₃ in four molten salt eutectics (3 LiCl?NaCl, 3 LiCl?2 KCl, LiCl?RbCl and 3 LiCl?2 CsCl) at 873 K. Cyclic voltammetry was used to determine the reduction potential for Eu^3+/2+ and the applied potentials for spectroelectrochemistry. Single step chronoabsorptometry and thin‐layer spectroelectrochemistry were used to obtain the number of electrons transferred, reduction potentials and diffusion coefficients for Eu³⁺ in each eutectic melt. The reduction potentials determined by thin‐layer spectroelectrochemistry were essentially the same as those obtained using cyclic voltammetry. The diffusion coefficient for Eu³⁺ was the largest in the 3 LiCl?NaCl melt, showed a negative shift in the 3 LiCl?2 KCl melt, and was the smallest in the LiCl?RbCl and 3 LiCl?2 CsCl eutectic melts. The basic one‐electron reversible electron transfer for Eu^3+/2+ was not affected by melt composition.     

阿霉素的光谱电化学研究

利用循环伏安、紫外可见光谱电化学、荧光光谱电化学、圆二色光谱电化学等方法研究了阿霉素(ADM)在石墨电极上的电化学行为.结果发现,阿霉素在+0.2～+0.7V和-0.2～-0.7V范围内分别出现一对氧化还原峰.正电位下,蒽环上的酚羟基发生单电子氧化,并伴随后续化学反应.负电位范围内,阿霉素经历ECE电极反应过程,即蒽醌经单电子还原生成半醌自由基,半醌可发生不可逆的化学反应,脱去配氧糖基,转变为7-去氧柔毛霉醌(7-deoxyadriamycinone),后者在更负的电位下形成一对可逆的新的氧化还原峰.     

茜素红S与脱氧核糖核酸相互作用的电化学研究

研究了茜素红S在玻碳电极上的电化学行为,根据茜素红S与DNA作用的伏安曲线、紫外．可见光谱及溴化乙锭对茜素红S与DNA作用的影响,认为茜素红S与DNA发生了嵌插作用。考察了温度、时间及pH值对二者作用的影响。     

Electrochemical reduction process of bilirubin in dimethylformamide

The electrochemical reduction behavior of bilirubin (BR) at platinum electrode in DMF was investigated by cyclic voltammetry, in situ electron spin resonance spectroscopy and in situ rapid scanning thin layer spectroelectrochemistry. Experimental results revealed that thereduction of BR firstly undergoes an ECE process: BR-+e BR-dimerize (BR)22- +e(BR)23-. The generated (BR)23- can be re-oxidized to BR and then to purpurin (Pu) by a series of oxidation processes:(BR)23- -e (BR)22- -2e 2BR, BR --2e BV --2e Pu. However, the re-reduction reactions of Pu are not the reverse processes. The different reduction mechanisms are discussed in detail.     

A Study on the Electrochemical and Electrochemiluminescent Behavior of Homogentisic Acid at Carbon Electrodes

The electrochemical oxidation and electrochemiluminescent behavior of homogentisic acid (HGA) has been studied in aqueous solutions over a wide pH range by linear sweep voltammetry, cyclic voltammetry, chronocoulometry at a glassy carbon electrode, by controlled potential electrolysis at a large area spectroscopic graphite electrode, and by spectroelectrochemistry at an optically transparent drilled holes graphite (DHG) electrode in a thin‐layer cell. The studies reveal that the electrochemical oxidation of HGA at carbon electrodes is a reversible process involving two‐electron, two‐proton transfer. In addition to the electrochemical oxidation, the chemical oxidation of HGA by dissolved oxygen was investigated by spectroscopic method combined with voltammetry. It was revealed that HGA is fairly stable in strongly acidic media but readily oxidized by dissolved oxygen in alkaline media giving rise to 1,4‐benzoquinone‐2‐acetic acid, the same product as that of electrooxidation of HGA. This oxidation product is stable in acidic, neutral and weakly alkaline media, but can further degrade in strongly alkaline media yielding oxalate as the final product. The electrochemiluminescent mechanism of HGA in the presence of Ru(bpy)₃²⁺ at a glassy carbon electrode was also investigated in detail, based on which a sensitive ECL method for determination of HGA was developed, and the detection limit was 3.0×10^?8 mol L^?1.     

Charged states of α,ω-dicyano β,β'-dibutylquaterthiophene as studied by in situ ESR UV-vis NIR spectroelectrochemistry

The influence of the molecular structure on the stabilization of charged states was studied in detail by in situ ESR UV-vis NIR spectroelectrochemistry at a novel α,ω-dicyano substituted β,β'-dibutylquaterthiophene (DCNDBQT) and the electrochemically generated cation and anion radicals have been proved for the first time. The voltammetry of DCNDBQT results in two separate oxidation steps with the reversible first one. The experimental absorption maxima at 646 and 1052 nm together with the calculated ones (by DFT method) as well as an ESR signal at the first anodic step prove the presence of a radical cation. Three additional optical bands (554, 906, and 1294 nm for CT-transition) can be attributed to the formation of cation radical dimer. The dicationic structure formed in the second oxidation step is not stable. The stabilization proceeds via a dimer formation in two chemical follow-up reactions. The existence of the dimeric structures was proved by ex situ MALDI TOF mass spectrometry. As the substitution by cyano groups opens the route to cathodic reductions, DCNDBQT shows a single quasi-reversible reduction step. Here, the in situ ESR UV-vis NIR spectroelectrochemical measurements and theoretical calculations let us confirm the electrochemical generation of an anion radical. As we found a low number of anion radicals by quantitative ESR spectroelectrochemistry and an appearance of additional bands in the UV-vis NIR absorption spectra, the formation of dimeric structures must be considered and was corroborated by mass spectrometry. The role of dimerization in the reaction mechanism of the DCNDBQT oxidation and reduction are discussed in general. The experimental results were interpreted using the quantum chemical calculations based on density functional theory.     

Enhanced reduction and determination of trace thyroxine at carbon paste electrode in the presence of trace cetyltrimethylammonium bromide.

The electrochemical response of thyroxine (T4) at a carbon paste electrode (CPE) in the presence of cetyltrimethylammonium bromide (CTAB) was investigated. It gave a well-defined oxidation peak at 0.80 V and a sensitive reduction peak at 0.40 V. Compared with the indiscernible signal in the absence of CTAB, the reduction current of T4 at CPE was greatly enhanced in the presence of CTAB, due to the interactions between T4, CTAB and the hydrophobic electrode surface. The electrode process of T4 was explored by cyclic voltammetry and chronocoulometry. The effect of surfactants on the reduction reaction proved that bromide ions (Br(-)) in CTAB might form special ion complexes with T4 via a special interaction with the iodine atoms on T4, which would activate the reduction of T4. The sensitive and selective reduction of T4 in this system was applied to the determination of T4 in drugs; a detection limit of 6.5 x 10(-9) M was obtained (sigma= 3).     

Mechanism of oxidation of 1-benzyl-1,4-dihydronicotinamide by the biologically active p-benzoquinone derivative, avarone, in a cationic micellar medium: An electrochemical approach

The electrochemical reduction of avarone (Q), an antitumor sesquiterpenoid quinone, was investigated at various pH in aqueous ethanol containing a cationic surfactant, cetyltrimethylammonium bromide (CTAB) by cyclic and rotating disc electrode voltammetry, using a glassy carbon electrode. Comparison of the electrochemical reduction of Q in presence of CTAB with the same process in a homogeneous water + ethanol solution shows an anodic shift of the reduction potential in the presence of CTAB; at pH > 9.5 and in presence of CTAB, two well-defined reduction peaks are observed, thus confirming one-electron reduction of Q, whereby the intermediate radical-anion is stabilized by the cationic micellar medium. The electrochemical oxidation of BNAH was investigated by cyclic voltammetry, and the anodic shift of the peak potential in presence of CTAB was observed. From the electrochemical behaviour of Q and BNAH, and the kinetics of the oxidation of BNAH with Q, it is suggested that the reaction takes place in two successive one-electron transfer steps. The application of the Marcus theory gives additional proof that, in this case, the first electron transfer is the rate determining step.     

Electrochemical oxidation of N-methylated derivatives of uric acid

The electrochemical oxidation of a number of N-methylated uric acids has been studied by linear and cyclic sweep voltammetry, coulometry and thin-layer spectroelectrochemistry. The observed results support the view that the electrooxidation is a 2e reaction to give a very unstable diimine primary product. This is rapidly hydrated to give an imine-alcohol which is further hydrated to give a uric acid-4,5-diol derivative which subsequently fragments to the various products.     

邻菲咯啉-铜(Ⅱ)-L-亮氨酸配合物与DNA的结合

应用循环伏安法、微分脉冲伏安法、电子吸收光谱和溴化乙锭(EB)荧光分析法研究了[Cu(phen)(H2O)(L-Leu)^ ](phen=1，10-邻菲咯啉，L-Leu=L-亮氨酸)与小牛胸腺DNA的相互作用。结果发现中心铜离子在循环伏安图上呈现一对明显的准可逆氧化还原波。当加入一定量的DNA时，配合物的氧化还原峰电流明显降低，配位阳离子的扩散系数减小，电子光谱的最大吸收峰明显红移，产生明显的减色效应。同时，配合物也能较大程度地猝灭EB-DNA体系的荧光，证明配合物与DNA存在插入结合。     

DTNB电化学行为的探讨

应用电解还原, 紫外和红外光谱及循环伏安等方法, 研究了DTNB在水溶液中和汞电极上的电化学行为。借助于电解还原和ESR技术, 首次检测到在DTNB电解还原中产生的自由基讯号。研究了该自由基的性质和动力学衰变规律。     

醌类衍生物捕获CO2的红外光谱电化学研究

采用现场红外光谱电化学技术, 研究了2,6-二氯苯醌(DCBQ)和2,6-二甲氧基苯醌(DMOBQ)在乙腈溶液中对CO₂的电化学捕获过程. 结果表明, 2种醌类衍生物在乙腈溶液中的电化学循环伏安(CV)曲线呈现2对氧化还原峰, 遵循连续两步单电子过程. 加入CO₂后, 由于取代基亲电性的不同, 2种衍生物发生了不同的变化: DCBQ仍然呈现2对氧化还原峰, 但是第二对还原峰发生了正移动; 而DMOBQ的2对氧化还原峰变成1对峰. 根据现场红外光谱分析结果分别得到了DCBQ和DMOBQ电化学捕获CO₂过程的不同机理. DCBQ是二价阴离子发生化学变化的电化学-电化学-化学(EEC)机理, 而DMOBQ则是还原产物一价阴离子自由基参与化学变化的电化学-化学-电化学(ECE)机理. 进一步对CO₂捕获过程进行了定量分析, 得出2种反应的化学计量比均为1∶1.     

Electrochemical and spectroscopic characterization of anodically formed nickel salen polymer films on glassy carbon, platinum, and optically transparent tin oxide electrodes in acetonitrile containing tetramethylammonium tetrafluoroborate

Anodically polymerized films of nickel salen formed on glassy carbon, optically transparent tin oxide, and platinum electrodes in acetonitrile containing tetramethylammonium tetrafluoroborate have been examined by means of cyclic voltammetry, thin-layer voltammetry, spectroelectrochemistry, and scanning electron microscopy. With the aid of thin-layer voltammetry, it has been confirmed that the global oxidative polymerization of nickel(II) salen involves three electrons per monomer. Polymerization proceeds through two distinct phases, the formation of which depend on the potential. Once the polymer film has been formed, the anodic process consists of the reversible one-electron nickel(III)/nickel(II) redox couple. Cyclic voltammetry along with spectroelectrochemistry has been employed to probe the roles of the nickel(III)/nickel(II) and nickel(II)/nickel(I) redox couples in the electrochemical response of the polymer film as well as the interconversion of the different oxidation states of nickel.     

Electrochemical Oxidation Mechanism of Ethidium Bromide at a Glassy Carbon Electrode

The electrochemical behavior of ethidium bromide (EtBr) on a glassy carbon electrode (GCE) was studied by cyclic, square wave and differential pulse voltammetry over a wide pH interval. The results revealed that the oxidation mechanism of EtBr is an irreversible and adsorption‐controlled electrode process that occurs in two consecutives steps. The first step is pH‐dependent and occurs at the amino group in the C8 position with the formation of ortho‐ and para‐quinone derivatives, while the second step is pH‐independent and occurs at the amino group in the C3 position. A square wave method for quantitative determination of EtBr is also proposed.