Fe(Ⅱ)-EDTA剪切DNA在悬汞电极上的电化学行为研究

在足迹图谱技术中,Fe(Ⅱ）-EDTA常被作为DNA断裂工具用于双链DNA的非特异性断裂^[1],因而Fe(Ⅱ）-EDTA作为核酸构象变化的探针及DNA－配体复合物分析的羟基自由基足迹试剂在生物化学、分子生物学和基因工程学等中获得广泛应用^[2]。虽然DNA在汞电极上的电化学行为研究报道较多^[3-7],但有关Fe(Ⅱ）-EDTA非特异性剪切DNA的电化学研究报道较少^[8-10]。本文对Fe(Ⅱ）-EDTA剪切DNA在悬汞电极上的电化学行为进行了初步研究。结果表明,由于Fe(Ⅱ）-EDTA对DNA的裂解作用,导致DNA的结构发生变化,使DNA在悬汞电极上的电化学行为发生变化,还原峰电流显著增大,因而用电化学方法研究DNA的裂解有望成为研究DNA结构变化的辅助手段。     

碳纳米管粉末微电极技术研究超氧自由基的电产生及化学性质

将多壁碳纳米管填充在粉末微电极尖端的小孔里制成碳纳米管粉末微电极,研究氧单电子还原产生超氧自由基的电化学行为.在二甲亚砜(DMSO)介质中,该电极反应是一个近乎可逆的还原/氧化过程,峰电位差(ΔEp)120mV,并显示出良好的稳态伏安曲线.根据极化曲线算得该电极反应的异相电荷传递速率常数ks=9.8×10-3cm/s.此外,还研究了超氧自由基的氧化性和碱性,并对相关反应过程作了讨论.     

氧在振动球磨石墨上阴极还原动力学的研究

石墨具有很好的导电性和化学稳定性而被广泛地用作电极材料,细粉状石墨对氧的电化学还原表现出相当好的催化活性^[1],氧在碳上的还原机理已经有许多人进行过研究[2,3],本工作中利用在真空条件下高速振动制备了超细振动球磨石墨,并运用旋转盘环电极技术研究了氧在这种石墨上的电化学还原机理。     

库仑滴定剂三价钒

五、四、三和二等价的钒均已用作容量分析中的滴定剂^[1],而用作库仑滴定剂的则只有五价和四价^[2,3].本工作探讨低价钒作为库仑滴定剂的可能.在酸性溶液中氧钒离子在铂电极上还原到三价钒的超电压大,在氢离子放电之前,氧钒离子无显著的电极还原^[4].     

钴(II)-丁二酮肟-亚硝酸盐体系极谱催化波的机理研究

在氨性底液(PH8)中, 钴(II)-丁二酮肟(DMG)-亚硝酸盐体系产生高灵敏的极谱催化波. 利用吸附伏安法, 测定下限可达1×10^-^1^1mol.dm^-^3Co. 我们用多种电化学方法和紫外可见分光光度法证明, 吸附在汞电极表面的[NH4]2[Co(DMG)2(NO2)2]是有很高电活性的混配化合物, 在复杂的电还原过程中, 不仅Co(II)和DMG被催化还原, 而且NO2^-也被催化还原, 从而产生很大的催化电流, 本文再一次证明, “活性钴"在催化波的形成过程中起着重要的作用.     

双酚A在纳米金-离子液体复合修饰电极上的电化学行为及测定

该文制备了纳米金-离子液体修饰电极(GNP-[BMIM]PF6/GCE),用红外光谱对GNP和[BMIM]PF6进行了表征.采用交流阻抗法研究了GNP-[BMIM]PF6/GCE的表面电化学特性,同时研究了双酚A(BPA)在该修饰电极上的循环伏安行为.结果表明,BPA在该修饰电极上出现1个氧化峰,无还原峰,为不可逆电化...     

苯亚甲基丙二腈在汞阴极上的还原反应

本文应用了多种电化学方法(循环伏安法,微分脉冲极谱法等)及UV光谱,GC-MS手段研究了苯亚甲基丙二腈(BDMN)在汞阴极上的还原过程.在0.03mol.L^-1四乙基溴化铵(TEAB),50%二氧六环-水介质中BDMN还原的微分脉冲极谱图上有两个峰,第一个峰是此分子中的双键还原,生成苄基丙二腈引起的,峰电位在-0.98V(vs.SCE).第二个峰的峰电位在-1.55V(vs.SCE),此峰是BDMN的水解产物苯甲醛还原为苯甲醇产生的.BDMN的整个电极反应为ECEC过程.此处,对BDMN及二氧六环在汞电极上的吸附现象也进行了研究.     

核黄素电化学还原研究

本文采用循环伏安、本体电解、荧光光谱、电子自旋共振波谱等技术对核黄素电化学还原机理进行了研究。结果表明,在DMSO溶液中,核黄素以质子化和非质子化两种形式存在,它们的还原电位分别是-0.78和-1.05(vs.SEC)。两种形式的核黄素都可在汞电极上得到一个电子,生成相应的自由基。自由基的g值分别为2.005和2.002。对质子化式的自由基的ESR超精细谱进行了理论分析,提出了核黄素可能的电化学还原机理。     

基于金纳米棒和超氧化物歧化酶层层自组装的超氧自由基生物传感器

超氧自由基（O2·-）检测对于研究氧化损伤有关的生化及病理过程具有重要意义.本文基于金纳米棒/超氧化物歧化酶层层自组装方法构建了一种新型超氧自由基电化学传感器.通过带正电的十六烷基三甲基溴化铵（CTAB）包裹的金纳米棒（AuNRs）与带负电的超氧化物歧化酶（SOD）在半胱氨酸（Cys）修饰的金（Au）电极上层层自组装制备了（SOD/AuNRs）2/Cys/Au电极,证明了金纳米棒/SOD双层组装膜能有效增强SOD与电极之间的电子转移,并且该电极中的SOD保持有良好的生物活性,可在还原电位下实现O2·-电催化还原,从而达到检测O2·-的目的.该超氧自由基电化学传感器表现出了良好的电分析性能,其检测线性范围为200nM～0.2mM,检测限为100nM（S/N=3）,灵敏度为22.11nAcm-2μM-1,响应时间为5s.此外,该传感器还显示了较好的稳定性以及排除常见共存物过氧化氢、尿酸和抗坏血酸等干扰的能力.因此,对于第三代超氧化物歧化酶传感器的制作来说,酶与纳米材料层层自组装方法能够提供一种有效的电极构建方式.     

钴(Ⅱ)-丁二酮肟-亚硝酸盐体系极谱催化波的机理研究

在氨性底液(pH8)中,钴(Ⅱ)-丁二酮肟(DMG)-亚硝酸盐体系产生高灵敏的极谱催化波.利用吸附伏安法,测定下限可达1×10~(-11)mol·dm~(-3)Co.我们用多种电化学方法和紫外可见分光光度法证明,吸附在汞电极表面的[NH_4]_2[Co(DMG)_2(NO_2)_2]是有很高电活性的混配化合物,在复杂的电还原过程中,不仅 Co(Ⅱ)和 DMG 被催化还原,而且 NO_2~-也被催化还原,从而产生很大的催化电流,本文再一次证明,“活性钴”在催化波的形成过程中起着重要的作用.     

Sb在Au电极上不可逆吸附的电化学过程

用电化学循环伏安法和电化学石英晶体微天平(EQCM)技术研究了Sb在Au电极上不可逆吸附的电化学过程. 研究结果表明, 在-0.25 V到0.18 V(vs SCE)范围内, Sb可在Au电极上稳定吸附, 并且在0.15 V附近出现特征氧化还原峰. 根据EQCM实验数据, 在电位0.18 V时, Sb在Au电极上的氧化产物是Sb2O3; 同时Sb的吸附阻止了电解液中阴离子和水在Au电极上的吸附. 当电极电位超过0.20 V时, Sb2O3会被进一步氧化成Sb5+化合物, 同时逐渐从Au电极表面脱附.     

Electrochemical characterization of a new system for detection of superoxide ion in alkaline solution

A new medium system containing dimethyldistearylammonium bromide (DSAB) was developed for the electrochemical detection of superoxide ion in alkaline solution. The reductions of molecular oxygen in alkaline media as a function of the electrode material were evaluated for Pt, Ag, Au and glassy carbon (GC) electrode. And a quasi-reversible redox process for the O₂/O₂⁻ couple was only obtained at the Pt electrode. The electrochemical responses of the O₂/O₂⁻ couple at a platinum electrode and a platinized platinum electrode were compared, which suggesting that the electrochemical behavior of the O₂/O₂⁻ couple was improved greatly at a platinized Pt electrode. The frequency change (mass change) on the surface of Pt electrode was characterized by the electrochemical quartz crystal microbalance. The reduction of the dissolved oxygen at a platinized Pt electrode in the presence of DSAB was also studied by using chronocoulometry and the result indicated that a one-electron reduction was involved. In addition, the scavenging activity of cysteine towards superoxide ion was evaluated by cyclic voltammetry.     

Electrochemical quartz crystal microbalance study of copper ad-atoms on gold and platinum electrodes Part I. Adsorption of anions in sulfuric acid

The deposition and dissolution processes of copper ad-atoms on a gold or a platinum electrode in sulfuric acid electrolyte solution were investigated by using the electrochemical quartz crystal microbalance. It was found that the weight loss in the removal of the Cu-adlayer from the Au substrate was considerably larger than that expected from Faraday's law whereas the deviation for the Pt substrate was very small. The adsorption of bisulfate or sulfate anions both on Cu ad-atoms and on the electrode substrates was discussed quantitatively. It was demonstrated that higher coverage with Cu ad-atoms and lower adsorbability with bisulfate or sulfate anions were obtained on the Pt electrode than on the Au, and these effects could be ascribed to the difference in electronegativity between Pt and Au substrates.     

Electrochemical Behavior of Irreversibly Adsorbed Sb on Au Electrode

The electrochemical processes of irreversibly adsorbed antimony (Sb_ad) on Au electrode were investigated by cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM). CV data showed that Sb_ad on Au electrode yielded oxidation and reduction features at about 0.15 V (vs saturated calomel electrode, SCE). EQCM data indicated that Sb_ad species were stable on Au electrode in the potential region from −0.25 to 0.18 V (vs SCE); the adsorption of Sb inhibited the adsorption of water and anion on Au electrode at low electrode potentials. Sb₂O₃ species was suggested to form on the Au electrode at 0.18 V. At a potential higher than 0.20 V the Sb₂O₃ species could be further oxidized to Sb(V) oxidation state and then desorbed from Au electrode.     

EQCM技术对电子传递促进机制的研究

本文报道了腺嘌呤存在时对超氧化物歧化酶在金丝电极上电化学行为的影响。并从电化学石英晶体微天平技术的测量结果，初步讨论了腺嘌呤对促进超氧化物歧化酶电子传递过程的作用机制。     

电化学石英晶体微天平研究碱性介质中单层级铂原子修饰的金电极上甲醇的电催化氧化

通过在Au电极表面欠电位沉积(UPD)Cu、再与Pt源(H2PtCl6或K2PtCl4)进行置换反应,制得单层级Pt原子修饰的金电极(对H2PtCl6或K2PtCl4,所制电极分别记为Pt(CuUPD-Pt4+)n/Au或Pt(CuUPD-Pt2+)n/Au,n表示欠电位沉积-置换过程的重复次数).用电化学石英晶体微天平(EQCM)技术定量研究了所制电极,评估了其在碱性环境中催化甲醇氧化的质量比活性(SECA).结果表明,以H2PtCl6为Pt源所制电极(Pt(CuUPD-Pt4+)3/Au)的活性更高,最大SECA高达35.7mAμg-1.根据EQCM结果计算了置换效率,籍此讨论了Pt原子在Au电极表面的层层组装结构,发现所制电极表面的裸Au位点分布百分数与实验结果(由AuOx还原峰电量测算)吻合.我们认为,EQCM技术是一种定量研究电极支撑的超薄催化剂的有效手段,这种高效的单层级贵金属催化剂有望在生物、能源、环境相关的电催化研究中进一步应用.     

Electrochemical deposition of poly(trans-[RuCl2(4-vinylpyridine)4]) and its reductive desorption: cyclic voltammetry and electrochemical quartz crystal microbalance studies

The electropolymerization of trans-[RuCl(2)(vpy)(4)](vpy = 4-vinylpyridine) on Au or Pt electrodes was studied by cyclic voltammetry and the electrochemical quartz crystal microbalance (EQCM) technique. Cyclic voltammetry of the monomer in DMSO on Au shows reductions at -2.0 and -2.2 V. Potential cycling over the first wave leads to polymer formation; however, scanning over the second wave leads to desorption of the polymer. These observations were confirmed by EQCM measurements which also revealed a high polymerization efficiency. Electrolysis, EQCM and XPS measurements showed that desorption was associated with substitution of chloride ligands by DMSO when the polymer was in a highly reduced state. The film also showed reversible mass changes due to the oxidation and accompanying ingress of charge-balancing anions and solvent into the film. Measurements on the dried films revealed that large quantities of solvent are trapped in the film during the electropolymerization process.     

Blocking properties of gold electrodes modified with 4-nitrophenyl and 4-decylphenyl groups

The electrochemical properties of Au electrodes grafted with 4-nitrophenyl and 4-decylphenyl groups have been studied. The electrografting of gold electrode surface with aryl groups was carried out by electroreduction of the corresponding diazonium salts in acetonitrile. The nitrophenyl film growth on gold was examined by atomic force microscopy, electrochemical quartz crystal microbalance and X-ray photoelectron spectroscopy. These measurements showed that a multilayer film of nitrophenyl groups was formed. Cyclic voltammetry was used to study the blocking properties of aryl-modified gold electrodes towards the Fe(CN)₆^3−/4− redox system. The reduction of oxygen was strongly suppressed on these electrodes as evidenced by the rotating disc electrode results.     

镀金和碳纳米管修饰金电极上吸附态葡萄糖氧化酶比活性的EQCM研究

采用石英晶体微天平(EQCM)技术监测了裸金电极、镀金和碳纳米管修饰金电极上葡萄糖氧化酶(GOD)的吸附过程. 通过EQCM测量吸附固定的GOD质量, 并实时检测酶反应产物H2O2的氧化电量, 求算了各表面上吸附态GOD的比活性(ESAi). 结果表明, 各表面上均可吸附一定的GOD, 且吸附态GOD均有一定的酶活性; 修饰CNTs可增大酶吸附量和酶电极对葡萄糖的响应电流, 但ESAi随CNTs修饰量的增大而降低; Au电极上电镀金后, 酶吸附量和酶电极对葡萄糖的响应电流亦增大, 但ESAi与裸金电极上的基本一致.     

The electrocatalytic reactions of adenine, guanine, H2O, H2O2, N2H4, and l -cysteine catalyzed by poly(Ni(4-TMPyP)) film-modified electrodes

Electrochemical preparation of poly(nickel tetrakis(N-methyl-4-pyridyl)porphyrin) tetratosylate (poly-Ni(4-TMPyP)) produces stable and electrochemically active films in strong and weak basic aqueous solutions. These films were produced on glassy carbon and gold electrodes. The electrochemical quartz crystal microbalance and cyclic voltammetry were used to study the in situ growth of poly(Ni(4-TMPyP)) films. The electrochemical properties of poly(Ni(4-TMPyP)) films indicate that the redox process was confined in to the immobilized film. The electrochemical quartz crystal microbalance results showed an ion exchange reaction for the redox couple. The polymer films showed one new redox couple when transferred to strong and weak basic aqueous solutions and the formal potential was found to be pH dependent. The electrocatalytic oxidation of H₂O by a nickel tetrakis(N-methyl-4-pyridyl)porphyrin film-modified electrode was also performed. The mechanism of oxygen evolution was determined by cyclic voltammetry, chronoamperometry and rotating ring disc electrode methods. The oxygen evolution was determined by a bicatalyst system using hemoglobin, and iron tetrakis (N-methyl-2-pyridyl)porphyrin as catalyst to detect the oxygen by electrocatalytic reduction. The electrocatalytic oxidations of adenine, guanine, H₂O₂, N₂H₄, NH₂OH, and l-cysteine by the film-modified electrode obtained from water-soluble nickel porphyrin were also investigated.