铂和铜电极上4-硝基吡啶-1-氧化物还原过程研究

4-氨基吡啶是一种重要的精细化工产品, 为探讨其电化学合成过程的反应机理, 采用循环伏安法、库仑电解等方法对强酸性条件下4-硝基吡啶-1-氧化物的电化学行为进行了研究. 结果表明: 4-硝基吡啶-1-氧化物在铂电极上主要经历电化学-化学-电化学(ECE)还原历程, 并生成4-羟胺吡啶-1-氧化物; 对铜电极而言, 当电位高于－0.65 V时主要经历ECE还原历程, 并生成4-羟胺吡啶-1-氧化物; 当电位低于－0.85 V时经历ECE还原历程生成的4-羟胺吡啶-1-氧化物, 可发生进一步4e^－还原, 并生成4-氨基吡啶.     

β-环糊精功能化石墨烯修饰电极同时测定邻硝基苯酚与对硝基苯酚

通过滴涂法制备了β-环糊精功能化石墨烯修饰玻碳电极(β-CD-GR/GCE),采用循环伏安法和二阶导数线性扫描伏安法研究了邻硝基苯酚(o-NP)和对硝基苯酚(p-NP)在该修饰电极上的电化学行为。实验结果表明,在该修饰电极上o-NP和p-NP的还原电流显著增加,两还原峰得到有效分离。在优化条件下,使用二阶导数线性扫描伏安法对o-NP和p-NP进行定量分析,线性范围分别为0.2~10μmol/L和0.06~10μmol/L,检出限分别为0.08μmol/L和0.02μmol/L。该法可用于环境水样中o-NP和p-NP的快速准确测定。     

1,5-二羟基萘作为伏安酶联免疫分析体系底物的研究

提出了1,5-二羟基萘(1,5-DHN)-H₂O₂-辣根过氧化物酶(HRP)伏安酶联免疫分析新体系. 1,5-DHN为非电活性物质, 但其在碱性B-R缓冲溶液中可被空气氧化生成5-羟基-1,4-萘醌, 此物质为电化学可还原物质, 产生良好的伏安还原峰. 加入H₂O₂和HRP后, HRP催化H2O2氧化5-羟基-1,4-萘醌生成3-羟基邻苯二甲酸, 从而使伏安还原峰降低. 利用伏安峰的降低可以测定HRP和HRP标记物的活性, 进而可用于测定各种抗原和抗体. 此伏安酶联免疫分析体系与以前所报道的伏安酶联免疫分析体系具有不同的反应机理. 以前报道的伏安酶联免疫分析体系在无HRP和H₂O₂时无伏安峰, 加入HRP和H₂O₂后, HRP催化H₂O₂氧化体系底物所得产物产生伏安还原峰, HRP浓度与还原峰高成正比, 而此体系为HRP浓度与伏安峰高的降低成正比. 将文中建立的伏安酶联免疫分析体系与酶联免疫吸附间接法相结合, 用于测定烟草花叶病毒(TMV)提纯液, 线性范围是25.0 ~ 340.0 ng/mL, 检测限是25.0 ng/mL.     

2,3-二取代-1,4-萘醌的合成

常温下, 在丙酮与水的混合介质中(V∶V＝1∶1), 4-羟基香豆素类化合物与1,4-萘醌进行Michael加成反应, 生成6个未见文献报道的2,3-二取代-1,4-萘醌. 产物经MS, 1H NMR, 元素分析表征, 确定了其化学结构.     

2-羟基-1,4-萘醌的电化学氧化还原机理研究

利用现场红外光谱电化学方法、 红外光谱循环伏吸法(CVA)和导数循环伏吸法(DCVA)研究了2-羟基-1,4-萘醌(2-HNQ)在乙腈溶剂中的电子转移机理. 在扫描范围为0.2~-1.8 V时, 2-HNQ的循环伏安(CV)图中有2对氧化还原峰. 在扫描范围为1.0~-2.0 V时, CV图在更正的电位下会出现1个氧化峰. 通过分析循环伏安扫描过程中1656, 1495, 1549和1325 cm^-1等峰的变化, 观察到整个电化学过程中存在2种中间状态, 去质子化醌(Q-O^-)还原生成的自由基二价阴离子会继续发生电化学反应, 即Q-O^-的还原遵循电化学-电化学反应机理(EE机理). 红外分析结果表明, 2-HNQ的电化学过程中存在较强的氢键作用.     

3-硝基苯酚在普鲁士蓝掺杂铜修饰电极上的电化学行为研究

采用循环伏安法制备了普鲁士蓝掺杂铜修饰电极(Cu/PB/GC),利用循环伏安、计时电量和电化学阻抗法研究3-硝基苯酚在该电极上的电化学行为。结果表明,此修饰电极显著提高了3-硝基苯酚的还原峰电流,电极反应在界面传质为线性扩散控制,扩散系数D为1.64×10~6cm~2/s,传递系数a为0.249,此电极可用来快速检测3-硝基苯酚。     

铌(V)-酒石酸-2-(5'-溴-2'-吡啶偶氮)-5-二乙氨基苯酚三元配便物的汞电极上的吸附

本文用线性变势吸附伏安法研究了铌(V)-酒石酸-2-(5'-溴-2'-吡啶偶氮)-5-二乙氨基苯酚三元配合物在汞电极上的电吸附性质, 测定了表面浓度, 讨论了吸附浓度的表达式及其与吸附时间、金属离子浓度、配位体浓度的关系, 验证了吸附量与电极面积及还原峰电流的关系。证明了配合物在电极上的还原是一个可逆吸附的还原过程。     

铌(V)-酒石酸-2-(5'-溴-2'-吡啶偶氮)-5-二乙氨基苯酚三元配便物的汞电极上的吸附

本文用线性变势吸附伏安法研究了铌(V)-酒石酸-2-(5'-溴-2'-吡啶偶氮)-5-二乙氨基苯酚三元配合物在汞电极上的电吸附性质, 测定了表面浓度, 讨论了吸附浓度的表达式及其与吸附时间、金属离子浓度、配位体浓度的关系, 验证了吸附量与电极面积及还原峰电流的关系。证明了配合物在电极上的还原是一个可逆吸附的还原过程。     

2,4,6-三硝基苯酚在掺杂了铕(Ⅲ)离子的类普鲁士蓝膜修饰的玻碳电极上的电催化还原反应

制备了用掺杂铕(Ⅲ)离子的类普鲁士蓝膜修饰的玻碳电极,并研究了2,4,6-三硝基苯酚在此修饰电极上的电化学行为.试验结果表明:与裸玻碳电极相比,2,4,6-三硝基苯酚在此修饰电极上的还原峰电流显著提高,还原电位大大降低,且工作曲线的线性范围明显增宽.在此基础上提出了一种高灵敏度直接测定2,4,6-三硝基苯酚的伏安测定法.在优化的条件下,测得特征还原峰的电流值与2,4,6-三硝基苯酚浓度在4.0×10-5～2.0× 10-3mol·L-及2.0× 101～8.0×10-6mol·L-1范围内呈线性关系,方法的检出限(3σ)为6.0×10×-8mo·L×-1.以黄河水样作为基体,用标准加入法做回收试验,测得回收率在97.7%～103.3%之间.     

2,4-二硝基苯酚在类普鲁士蓝修饰电极上的电化学行为及分析应用研究

利用电化学沉积法制备了稀土铕(Ⅲ)离子掺杂的类普鲁士蓝化学修饰电极(Eu-PB/GC/CME),采用循环伏安法(CV)和示差脉冲伏安法(DPV)研究了该修饰电极上2,4二-硝基苯酚的电化学行为。结果表明,该修饰电极与裸电极相比能显著提高2,4二-硝基苯酚的还原峰电流,还原电位降低53 mV,线性范围明显增宽。还讨论了支持电解质种类、酸度、修饰层厚度和扫速等因素对2,4二-硝基苯酚伏安响应的影响。在优化的实验条件下,2,4二-硝基苯酚的示差脉冲峰电流(Epc=-341 mV)与浓度在2.0×10-5~2.0×10-3mol/L和2.0×10-7~8.0×10-6mol/L范围内分别呈良好的线性关系,回归方程为ipc(μA)=9.821×104c(mol/L) 22.142(r=0.9992,n=10)和ipc(μA)=4.2025×105c(mol/L) 0.3720(r=0.9967,n=8),检出限(3σ)为6.0×10-8mol/L。该电极用于模拟废水样中2,4二-硝基苯酚的测定,回收率为97.3%~103.0%,结果令人满意。     

硝基苯在铜电极上的电还原特性研究

应用循环伏安法和线性扫描伏安法研究水溶液中硝基苯在铜电极上的电还原特性及其电还原为苯胺的中间步骤和反应机理.结果表明:铜电极上硝基苯的还原电位在-0.58V和-1.32V左右(vs.SCE),溶液的酸性和碱性均有益于该还原反应的发生;还原过程伴有反应物吸附现象,当硝基苯浓度较大时,还原过程受传质过程控制;随着厌氧程度的提高,还原速率加快.     

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.     

Electrochemistry of triphenyltin acetate at a mercury-film glassy carbon electrode

The electrochemical behaviour of triphenyltin acetate was investigated by cyclic voltammetry, differential-pulse voltammetry and controlled potential electrolysis at a mercury-film glassy carbon electrode. Effects on the electrochemical response of the composition of supporting electrolytes, pH, electrode rotation speed and triphenyltin acetate concentration were determined. The electrochemical reduction of this compound was found to involve a preliminary adsorption process (E_peak ≈ ?0.7 V vs. SCE), the reduction of triphenyltin acetate to the triphenyltin radical (E_peak ≈ ?1.0 V) and reduction of the radical to the triphenyltin anion (E_peak ≈ ?1.4 V). A procedure for the determination of trace amounts of this compound by differential-pulse anodic stripping voltammetry in 50% (v/v) ethanol with 0.1 M acetic acid + 0.1 M ammonia solution was developed and applied to the analysis of a commercial powder formulation and water and fish samples. The limit of detection was 2.5 × 10^?9 M triphenyltin acetate.     

酸性大红3R的电化学研究及应用

采用循环伏安法和方波伏安法考察了酸性大红3R在碳糊电极上的伏安行为和反应机理。当扫描速率为0.1 V/s时,在pH 1的0.05 mol/L H2SO4支持电解液中,酸性大红3R有一对峰电位分别是0.74 V和0.72 V（vs.饱和甘汞电极）的氧化峰和还原峰,并且显示吸附控制的2电子单质子的准可逆氧化还原过程。在最佳实验条件下,酸性大红3R的方波氧化峰峰电流与其浓度在2.12×10^-5-3.39×10^-4mol/L范围内呈线性关系,检出限为8.35×10^-6mol/L,由此建立测定酸性大红3R含量的方波伏安法。该方法可用于计算酸性大红3R常规染羊毛与蚕丝的上染率,测定结果与分光光度法一致。     

甲基对硫磷在聚噻吩/纳米二氧化钛修饰玻碳电极上的电化学行为及其测定

用循环伏安法(CV)、线性扫描溶出伏安法(LSSV)研究了甲基对硫磷(MPT)在聚噻吩/纳米二氧化钛修饰玻碳电极(PTh-NTiO2/GCE)上的电化学行为.实验表明,该修饰电极能显著提高MPT的氧化还原峰电流,在B-R缓冲溶液(pH 5.72)中,于-0.662V( vs.SCE)处产生灵敏的不可逆还原峰,其峰电流与...     

LiF-BaF2-LiCl熔盐体系中Li+的电化学行为

运用三电极在电化学工作站AUTOLAB以循环伏安法、计时电流法和计时电位法研究了LiF-BaF₂-LiCl熔盐体系中1203 K温度下锂在钨（W）电极上的电化学还原过程及其控制步骤. 结果表明,Li⁺在W电极上的还原过程是一步得电子的准可逆反应,析出电位在-1.0 V附近. 阴极过程受离子的扩散步骤控制,计算得出扩散系数为4.5 × 10^-6 cm²•s^-1.     

Investigation of Electrochemical Behavior of Some Dithiophosphonates in Acetonitrile on the Platinum and Gold Electrodes

Some dithiophosphonate derivatives were synthesized and the electrochemical reduction mechanism was investigated by cyclic voltammetry (CV), square wave voltammetry (SWV) and chronoamperometry (CA) in 0.1 M tetrabutylammoniumtetrafluoroborate (TBATFB) in acetonitrile at platinum (Pt) and gold (Au) electrodes. Dithiophosphonates showed a cyclic voltammetric reduction peak at about ?1.1 V at Pt and ?1.3 V at Au electrode (vs. Ag/Ag⁺) in this media. It was also shown that dithiophosphonates can be determined quantitatively in acetonitrile using a calibration graph. The number of electrons transferred were calculated as 2 using ferrocene as a reference compound at the UME electrode. Mechanism of dithiophosphonates was also examined on Pt and Au electrodes and electrochemical reduction of dithiophosphonates seems to follow an EC mechanism with an irreversible electron transfer step. The reaction product in the bulk electrolysis experiment was isolated and identified using proton‐coupled P‐31 NMR, ¹³C‐NMR and IR spectroscopy. The adsorption tests for dithiophosphonates were revealed that no strong or weak adsorption phenomena exist on both Pt and Au electrodes. Simulation curves were acquired by DigiSim 3.03 version to investigate the reduction mechanism and to estimate the kinetic parameters for electrochemical and chemical steps.     

Electrochemical Reduction of Nitrobenzene in Ionic Liquid BMImAc

Ionic liquid,1-butyl-3-methylimidazolium acetate（BMImAc）,was used in the electrochemical reduction of nitrobenzene.The electro-reduction of nitrobenzene on platinum electrode was studied by cyclic voltammetry（CV）,in situ Fourier transform infrared（FTIR） spectroscopy and constant-potential electrolysis.The experimental results show that electrochemical reduction process of nitrobenzene was controlled by diffusion,the main reduction product was azobenzen at-1.45 V,and the influences of scan rate and temperature on the electrochemical behaviors were obviously.A reduction mechanism of nitrobenzene in an ionic liquid was a probable ‘nitrobenzene→nitrosobenzene→azobenzene→aniline＇ main reductive reaction route.     

The influence of cetyltrimethyl ammonium bromide on electrochemical properties of thyroxine reduction at carbon nanotubes modified electrode

The effect of cetyltrimethyl ammonium bromide (CTAB) on the electrochemical behaviors of thyroxine at a glassy carbon electrode (GCE) modified with single-walled carbon nanotubes (SWNTs) was investigated. At the SWNTs film-coated GCE, a well-defined oxidation peak of thyroxine at 0.78 V was obtained, but the reduction peak of thyroxine was indiscernible. When trace CTAB was added to the working solution, the reduction current could be greatly enhanced and the oxidation current remained stable. The reaction mechanisms for the reduction of thyroxine were explored by chronocoulometry. Thyroxine might form particular ion complex with CTAB via the interaction between iodine atoms on thyroxine and bromide ions in CTAB, which made the concentration of thyroxine at the surface of the modified electrode increased and the electron transfer rate enhanced. The proper mechanisms for the enhanced reduction of thyroxine in the present of CTAB were explored by several electrochemical techniques including cycle voltammetry linear sweep voltammetry and others. It was concluded that the special interactions between the thyroxine CTAB and SWNTs resulted in the increase of the reduction peak current. All results indicated that two iodine atoms on the thyroxine and four electrons were involved the reduction process which was irreversible and two iodine ions produced. In this system, the sensitive reduction peak of thyroxine at 0.3 V was employed to determine thyroxine and a low detection limit of 2x10(-8) mol/L was obtained for 2 min accumulation at 0.9 V. The SWNTs coated GCE had good stability and reproducibility.     

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.