基于ITO电极的细胞色素c吸附层的直接电化学

采用未经修饰的铟锡氧化物(ITO)工作电极直接探测到了细胞色素c(Cytc)吸附层的氧化还原峰,并得出了Cytc的表面浓度,随着溶液浓度从2μmo·lL-1增大到10μmo·lL-1,Cytc的表面浓度相应地从0.35×10-12mo·lcm-2增大到1.53×10-12mo·lcm-2.实验获得的表面浓度倒数与溶液浓度倒数的准线性关系说明Cytc在ITO表面的吸附基本满足Langmuir等温吸附理论.对Cytc溶液的循环伏安测试结果表明参与电极反应的Cytc包括游离分子和吸附分子,前者的贡献大于后者,电极反应主要受扩散控制并呈准可逆过程.根据Nicholson方法估算得到反应物的标准异相速率常数的平均值为1.65×10-3cm·s-1.实验结果显示在室温下放置1h后Cytc吸附层电化学活性部分丧失,在80℃下放置1h后吸附层完全失活.失活的Cytc吸附层对铁氰化钾溶液在Au电极上的电极反应具有明显的阻碍作用.     

Adsorption behavior of bis (2-ethylhexyl) sodium sulfosuccinate (AOT) at the mercury-electrolyte solution interface as a function of electrode potential and time

The dependence of the differential capacitance (C) of the electrode double layer of a hanging mercury drop electrode in bis (2-ethylhexyl) sodium sulfosuccinate (AOT) solutions on electrode potential (E) and time is measured using three-dimensional phase sensitive ac voltammetry. This methodology, possessing a very wide time window that permits a detailed study of the adsorption phenomena, is based on the reconstruction of C vs E curves, sampled after many phase-sensitive ac chronoamperometric experiments. The shape of these curves allows an estimation of the structure of the layer of AOT molecules absorbed at the electrode surface. AOT molecules form micelles in bulk solutions and they also associate in the charged interface under the strong influence of the electric field into surface aggregates which depend on their concentration and applied potential. The presence of AOT micelles in the bulk solution can be linked with the appearance of a surface film at potentials more negative than those corresponding to a condensed film linked with a capacitance value slightly higher than that normally attributed to a compact layer. The whole phenomenon is proved to be very dependant upon time.     

姜黄素的电化学性质及其测定

在0.1 mol/L磷酸盐缓冲液(pH 3.0)中,姜黄素于玻碳电极上存在可逆的单电子转移过程,据此,本文建立了以差示脉冲伏安扫描法检测姜黄素含量的新方法.在+0.8V(vs.SCE)电位下,含姜黄素的电解液(试样)于玻碳电极上经过富集,可得一灵敏的还原峰,峰电位Ep为+0.386V.峰电流Ip与姜黄素浓度(1.0×10-8~2.5×10-7mol/L范围内)成线性关系,最低检出限为4.0×10-9mol/L.本法操作简单、快速、灵敏、准确,可用于药物中姜黄素含量直接测定.     

A study on electrochemistry of histidine and its metabolites based on the diazo coupling reaction

The diazo coupling reaction of diazotized p-aminoacetophenone (DPAAP) with histidine and its metabolites form the basis of the differential pulse adsorption stripping voltammetry (DPASV) method for determination of histidine and its metabolites. The adsorption and electrochemical reaction mechanism of the coupling products were studied in detail by structure analysis, cyclic voltammetry, chronocoulometry, control potential electrolysis, electrocapillary curves, UV spectroscopy and the effect of temperature and surfactants. The adsorption of azo-histidine was found to obey Frumkin adsorption isotherm. The calculation results of the maximum surface excess (Gamma(m)=3.08x10(-11) mol cm(2)), diffusion coefficient (D=2.27x10(-6) cm(2) s(-1)), adsorption coefficient (beta=1.06x10(7)) and interactive factor (gamma=0.9900) showed that the azo-histidine conjugation molecules adsorbed on the mercury electrode surface were attracted each other and the electrode process was adsorption controlled.     

基于门控制电催化效应的分子印迹传感器

以绿麦隆为模板分子,在镍电极表面聚合制得绿麦隆分子印迹膜。洗脱后的分子印迹膜重新吸附不同浓度绿麦隆分子,在印迹膜上形成不同量的印迹孔穴,H2O2通过印迹孔穴在镍电极表面产生电催化氧化,从而形成门控制电催化效应,以此对绿麦隆进行定量分析。研究表明,镍电极对H2O2有较好的催化效果,分子印迹聚合膜中模板分子、功能单体和交联剂的摩尔配比为1∶12∶30,重吸附时间为10 min,测试缓冲液pH=7.2。H2O2的催化电流值与绿麦隆浓度在1.0×10-4～4.0×10-7 mol/L范围内呈良好的线性关系;检出限为2.9×10-8 mol/L。将传感器应用于农田水样的检测,其回收率在97%～103%之间。     

柚皮苷分子印迹传感器的制备与应用

以邻氨基酚为单体,无电化学活性的柚皮苷为模板分子,采用循环伏安法(扫速为100mV/s)在碳电极上往复扫描30次,电聚合出具有识别柚皮苷分子功能的敏感膜。以扫描电子显微镜(SEM)、X射线全反射(XRR)及电化学方法对该印迹传感器进行表征。结果表明,印迹传感器敏感膜与非印迹膜在形貌结构和电化学特性方面有明显的不同。此传感器对柚皮苷有较好的选择性,响应快(30s),在6.0×10-5～1.4×10-4mol/L范围内呈线性关系,且重现性好(RSD=1.8%,n=5);传感器对柚皮苷的检出限为1.6×10-5mol/L。     

聚拉莫三嗪修饰玻碳电极测定痕量铜(Ⅱ)的研究

在稀H2SO4介质中,采用循环伏安法制备了聚拉莫三嗪膜修饰玻碳电极(PLTG/GCE),将制得的膜修饰电极(PLTG/GCE)在一定电位下选择性预富集Cu(Ⅱ),并用差分脉冲溶出伏安法测定.结果表明,该膜修饰电极对Cu(Ⅱ)的富集作用明显强于裸玻碳电极.对电聚合条件、富集和溶出介质、富集时间及富集电位等实验参数进行了考察,在优化实验条件下,Cu(Ⅱ)的浓度在4.0×10-9～1.3×10-7mol· L-1范围内与溶出峰电流呈线性关系,相关系数为0.9999,检出限为1.5×10-9 mol·L-1.该修饰电极具有较高的灵敏度和选择性,用于实际水样的分析,平均回收率为98.7％.     

羧基化碳纳米管修饰碳糊电极伏安法测定食盐中碘酸根

应用羧基化多壁碳纳米管(c-MWCNT)修饰碳糊电极,测定食盐中的碘酸根含量.在0.1 mol/L的NaOH电解液中,当IO3-在羧基化多壁碳纳米管修饰碳糊电极表面富集60 s,电位扫速为300 mV/s时,该修饰电极在线性扫描伏安图上能出现一灵敏的阴极溶出峰,峰电位为-0.52 V,峰电流与IO3-浓度在8.0×10-10~5.0×10-8mol/L和1.0×10-7~3.0×10-6mol/L的范围内成良好线关系,相关系数分别为0.999和0.998,检出限可达1.0×10-11mol/L;该修饰电极无汞,稳定性较好,用于加碘食盐中碘酸根含量的测定灵敏度高,平均回收率为101.1%.循环伏安(CV)测试表明,碘酸根在修饰电极上电化学反应是一不可逆过程,其电极反应标准均相速率常数为0.0109 cm.s-1.     

铅于旋转银盘电极上欠电位沉积的计时库仑法研究

用计时库仑法研究了Ｐｂ２＋于旋转Ａｇ盘电极（Ａｇ－ＲＤＥ）上的欠电位沉积（ＵＰＤ）性质。实验证明,支持电解质（０．０１ｍｏｌ／Ｌ　ＨＮＯ３＋０．０１　ｍｏｌ／Ｌ ＮａＣＩ）中Ｃｌ－离子的存在有利于取得稳态条件下ＵＰＤ Ｐｂ的电量值。其氧化过程电量（Ｑａ）,代表Ｐｂ２＋吸附单层被定量转化为ＵＰＤ Ｐｂ单层的量,Ｑａ的平均值为３９３．３μＣ／ｃｍ２,相应于２×１０－９ｍｏｌ／ｃｍ２Ｐｂ２＋表面复盖量。     

Studies on the effect of electrode pretreatment on the coverage of self-assembled monolayers of dodecanethiol on gold by electrochemical reductive desorption determination

This paper examines the effect of five major pretreatments on the surface coverage Γ(m) of dodecanethiol self-assembled monolayer on polycrystalline gold electrode (C(12)SH-SAMs-Au). It is based on the electrochemical reductive desorption in the alkaline solution by cyclic voltammetry (CV). The five different pretreatment methods include: aqua regia pretreatment, reductive annealed pretreatment, UV/O(3) pretreatment, piranha reagents pretreatment and simple polishing pretreatment, and then all above pretreatments following the same procedure of electrochemistry cleaning. The experimental results show that the surface coverage Γ(m) for C(12)SH-SAMs-Au by the five pretreatment methods are: aqua regia pretreatment (8.0 × 10(-10) mol cm(-2)) ~ reductive annealed pretreatment (7.8 × 10(-10) mol cm(-2)) > UV/O(3) pretreatment (5.0 × 10(-10) mol cm(-2)) ~ piranha reagents pretreatment (4.1 × 10(-10) mol cm(-2)) ~ simple polishing pretreatment (4.0 × 10(-10) mol cm(-2)). This indicates that Au surfaces pretreated by aqua regia and reductive annealing can achieve the best results, and the Γ(m) values obtained are consistent with the theoretical coverage values (Γ(m) ≈ 8.0 × 10(-10) mol cm(-2)); however, the Γ(m) values for other three pretreatment methods (UV/O(3), piranha reagents and simple polishing) are not satisfactory, obtaining only almost half of the theoretical Γ(m) value. Thus, we recommend aqua regia and reductive annealed pretreatments as the best methods for self-assembling the alkyl thiol monolayer (C(n)SH-SAMs-Au), whereas UV/O(3), piranha reagents and simple polishing pretreatments are not recommended.     

Electrochemical and microscopic characteristics of thiolipid layers as simple models of cell membranes

The thiolipid 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol (DPPTE) has been proposed as a component of a simple model of cell membranes, which can be used for the studies of the interactions with drugs and other biologically important species. Depending on the deposition technique, Langmuir-Blodgett method or self-assembly, the obtained model membranes exhibit differences in the organization and properties, as shown by electrochemical techniques. The surface concentration and area per molecule of DPPTE model membranes were determined using chronocoulometry, which gives more reliable results than the widely used reductive desorption method. The mean surface concentration of self-assembled DPPTE monolayer deposited on gold electrode is equal to 4.52 × 10(-10) mol·cm(-2), which corresponds to the area per molecule of 36.7 ?(2). Moreover, model membranes prepared by means of LB method tend to be less compact than self-assembled DPPTE monolayers. Adsorption/desorption behavior of the DPPTE molecules on Au(111) was also visualized by EC-STM method. At the beginning of the process at negative potentials, the physisorbed molecules formed a flat-lying adlayer. Changing the potential in the positive direction resulted in the formation of Au-S bonds, and as a consequence the upstanding phase with higher packing density was observed. The thickness of such a layer determined by atomic force microscopy method is equal to 2.08 nm and corresponds to that of a monomolecular film.     

Enhanced electrochemiluminescence employed for the selective detection of methyl parathion based on a zirconia nanoparticle film modified electrode

A simple, rapid and sensitive electrochemiluminescence (ECL) sensor was proposed for direct measurements of methyl parathion (MP) based on the strong affinity of a nano zirconia particles (ZrO(2) NPs) modified film on the electrode to the phosphoric group. ZrO(2) NPs, which could provide a larger absorption area to immobilize organophosphorus, was firstly modified on the glassy carbon electrode surface to prepare the proposed ECL sensor (ZrO(2)/GC). Subsequently, the ZrO(2)/GC electrode was scanned from -0.8 to +0.6 V to obtain the background signal at 0.44 V in a luminol/KCl solution. Then, a certain concentration of MP was added to an aqueous solution for 240 s, which was absorbed onto the ZrO(2)/GC electrode surface. Moreover, the MP absorbed on the surface of the ZrO(2)/GC electrode enhanced the ECL signal of luminol in the luminol/KCl solution, which increased with the concentration of MP. As a result, a novel ECL sensor was obtained in a luminol/KCl solution. The MP was determined in the range of from 3.8 × 10(-11) to 3.8 × 10(-6) mol L(-1), with a low detection limit of 1.27 × 10(-11) mol L(-1) (S/N = 3). The proposed ECL sensor performance for MP detection will open a new field in the application of rapid and screen detection of ultra-trace amounts of organ phosphorus pesticides (OPs) of vegetables used in farm markets.     

纳米氧化铁修饰玻碳电极检测痕量镉离子

制备了一种纳米氧化铁修饰玻碳电极,并研究了镉离子在该修饰电极上的溶出伏安行为。结果表明,纳米氧化铁颗粒能有效促进镉离子的溶出伏安响应。在pH 6.0的磷酸缓冲溶液中,镉离子能有效吸附在纳米氧化铁表面并在-1.0 V时被还原。被还原的镉在正向扫描过程中可以重新氧化,并在-0.85 V处出现一明显的溶出伏安氧化峰。该峰电流随镉离子浓度的增大而增大,可用于对镉离子的检测。在最佳检测条件(pH 6.0,富集时间350 s,富集电位-1.0 V)下,镉离子的响应电流与其浓度在6.0×10-10～1.0×10-8mol/L以及1.0×10-8～1.0×10-5 mol/L范围内呈良好线性,检出限(S/N=3)为1.0×10-10 mol/L。干扰实验结果表明,一些常见的阳离子以及阴离子对镉离子的检测无明显干扰。将该方法用于实际样品的检测,回收率良好。     

卡维地洛的电化学测定及与牛血清白蛋白相互作用的研究

建立了测定卡维地洛(CAR)新的电化学方法.结合紫外、红外光谱分析,研究了CAR与牛血清白蛋白(BSA)的相互作用.实验发现,在pH4.0Britton-Robinson(B-R)缓冲溶液中,CAR在碳糊电极上产生3个不可逆的氧化峰.以0.92V处的氧化峰为研究对象,结果发现峰电流Ipa,1与CAR浓度在2.45×10-5～1.19×10-3mol/L范围呈良好的线性关系,CAR的检出限为5.6×10-6mol/L.当BSA加入CAR溶液后,CAR峰电流降低,氧化峰电流的降低值△Ipa,1与BSA的浓度在2.92×10-7～1.09×10-5mol/L范围内呈良好线性关系,BSA的检出限为4.1×10-8mol/L.电化学结果表明,CAR与BSA之间形成1∶1的结合物,结合常数为3.14×106L/mol.紫外光谱表明CAR的加入使BSA的吸收峰发生红移且有增色效应.红外光谱表明CAR与BSA分子中氨基酸残基的硫及氮原子形成键合作用.     

Electrochemical determination of methimazole based on the acetylene black/chitosan film electrode and its application to rat serum samples

A novel method has been developed for the determination of methimazole, which was based on the enhanced electrochemical response of methimazole at the acetylene black/chitosan composite film modified glassy carbon electrode. The electrochemical behavior of methimazole was studied at this film electrode by cyclic voltammetry and differential pulse voltammetry. The experimental results showed that methimazole exhibited a remarkable oxidation peak at 0.63V at the film electrode. Compared with the bare glassy carbon electrode, the oxidation peak current increased greatly, and the peak potential shifted negatively, which indicated that the acetylene black/chitosan film electrode had good catalysis to the electrochemical oxidation of methimazole. The enhanced oxidation current of methimazole was indebted to the nano-porus structure of the composite film and the enlarged effective electrode area. The influences of some experimental conditions on the oxidation of methimazole were tested and the calibration plot was examined. The results indicated that the differential pulse response of methimazole was linear with its concentration in the range of 1.0×10(-7) to 2.0×10(-5)mol/L with a linear coefficient of 0.998, and in the range of 4.0×10(-5) to 3.0×10(-4)mol/L with a linear coefficient of 0.993. The detection limit was 2.0×10(-8)mol/L (S/N=3). The film electrode was used to detect the content of methimazole in rat serum samples by the standard addition method with satisfactory results.     

SFG study of the ethanol in an acidic medium--Pt(110) interface: effects of the alcohol concentration

Ethanol in an acidic solution-Pt(110) interface was studied by SFG spectroscopy (between 1820 and 2325 cm(-1)) to explore primarily the effects of the alcohol concentration. Stretching bands of H-Pt (ca. 1970 or 2050 cm(-1)) and CO (ca. 1980 and 2040 cm(-1)) species, produced by the ethanol oxidation, were detected during the adsorption and oxidation of 0-1 mol L(-1) ethanol in a 0.1 mol L(-1) HClO(4) solution on the electrode surface. Hydrogen and CO coadsorb stably on Pt(110) between 0.05 and 0.15 V in ethanol-containing solutions. In this potential range, the blue shift of the hydrogen resonance (ca. 80 cm(-1)) reveals a weakening of the hydrogen bonding between adsorbed hydrogen and water molecules in the double layer. After the hydrogen desorption (0.15 V), the formation of compact CO islands, depending on the ethanol concentration, lifts the Pt(110) surface reconstruction. In ethanol-free solution, the surface remains reconstructed. The lower-frequency CO band is assigned to the CO species adsorbed on (1 x 2) reconstructed Pt(110) domains, having smaller local coverages, while the higher-frequency CO band is attributed to the close-packed CO species adsorbed on (1 x 1) patches. The reaction pathway forming CO(2) is less favored with increasing ethanol concentration.     

三磷酸腺苷在TiO2掺杂碳纳米纤维修饰电极上的电化学行为

采用循环伏安法和示差脉冲伏安法研究了三磷酸腺苷(ATP)在TiO2掺杂碳纳米纤维(TiO2@CNF)修饰的碳离子液体电极表面(TiO2@CNF/CILE)的电化学行为。结果表明,ATP在TiO2@CNF/CILE表面有一个明显的氧化峰,在pH 3.0的Britton-Robinson(BR)缓冲溶液中修饰电极对ATP具有显著的电催化作用。纤维状的TiO2@CNF能够有效促进电子转移,增加电化学信号。当ATP浓度分别在4.0×10^-9~2.0×10^-6mol/L和2.0×10^-6~1.0×10^-4mol/L范围时,氧化峰电流与ATP浓度呈良好的线性关系,检测限为1.4 nmol/L。修饰电极可用于注射液中ATP的测定。     

阿西美辛的吸附伏安特性

在乙酸 -乙酸钠 ( p H 4.2 0 )底液中 ,阿西美辛 ( ACE)在汞电极上有一线性扫描还原峰 ,峰电位 Epc=- 1 .1 8V( vs.Ag/Ag Cl) ,该峰具有明显的吸附性。吸附粒子为 ACE中性分子 ,测得 ACE在汞电极上的饱和吸附量为 1 .1 9× 1 0 - 10 mol/cm2 ,每个 ACE分子所占电极面积为 1 .43nm2 ,ACE在悬汞电极上的吸附符合 Frumkin等温式。测得吸附系数β =1 .2 9× 1 0 6 ,吸引因素γ =1 .0 4 ,电子转移数 n为 2 ,不可逆吸附的电子转移系数α为 0 .86,表面电极反应速率常数 ks=0 .32 /s。建立了吸附伏安法测定 ACE的最佳条件 ,检出限为 1 .0× 1 0 - 9mol/L     

Highly sensitive voltammetric sensor based on catechol-derivative-multiwall carbon nanotubes for the catalytic determination of captopril in patient human urine samples

A new catechol-derivative compound, N-(3,4-dihydroxyphenethyl)-3,5-dinitrobenzamide, was synthesized and used to construct a modified-carbon nanotubes paste electrode. The electro-oxidation of captopril at the surface of the modified electrode was studied using cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Under the optimized conditions, the differential pulse voltammetric peak current of captopril increased linearly with captopril concentration in the ranges of 6.4×10(-8) to 3.2×10(-48) mol L(-1). The detection limit was 3.4×10(-8) mol L(-1) captopril. The diffusion coefficient and kinetic parameters (such as electron transfer coefficient and the heterogeneous rate constant) for captopril oxidation were also determined. The RSD% for 0.5 and 10.0 μmol L(-1) captopril were 2.1% and 1.6%, respectively. The proposed sensor was successfully applied for the determination of captopril in human patient urine and tablet samples.     

水滑石负载的钯纳米粒子对水合肼的电催化氧化

利用共沉淀方法制备了载体水滑石(LDH), 通过离子交换法将PdCl2₄^- 插入水滑石层间, 再用水合肼将其还原, 制备得到了水滑石负载的分散状钯纳米粒子(LDH-Pd⁰). 利用X射线衍射(XRD)、透射电镜(TEM)和X射线电子能谱(XPS)等手段对所得样品进行了表征, 结果表明钯纳米粒子能很好地分散在水滑石上. 将该纳米材料修饰的玻碳电极(GCE)用于水合肼的电催化氧化, 该修饰电极表现出很好的电化学催化活性. 用循环伏安法(CV)、计时库仑法(CC)和计时安培法(i-t)对修饰电极的催化活性、有效表面积和水合肼的催化氧化机理等进行了研究. 结果表明水合肼在-0.1 V附近有明显的氧化峰, 在1.0×10^-5-2.0×10^-4 mol·L^-1范围内, 阳极峰电流与水合肼浓度间有良好的线性关系, 其检测限为9.5×10^-7 mol·L^-1. 计算得到GCE, LDH-Pd⁰/GCE 和LDH/GCE电极活化面积分别为0.02089, 0.02762 和0.02496 cm². 推知水合肼的氧化过程有4 电子和4 质子参与, 并且其在电极上的反应是受扩散控制的不可逆过程.