NADH在邻苯二酚紫修饰石墨电极上的电催化氧化

以吸附在石墨电极上的邻苯二酚紫作为电子传递媒介体构成修饰电极。在－０．４０－＋０．６０Ｖ电位区间内，吸附态的邻苯二酚紫表现出相当可逆的氧化，还原行为，电极反应为单电子过程并有１个质子参加。在ｐＨ为７．０的磷酸盐缓冲溶液中，其式量电位Ｅ＾ｏ＇为０．１０Ｖ，表观电极反应速率常数ｋｓ为５．５ｓ＾－＾１。邻苯二酚紫修饰电极对还原型烟酰胺腺嘌呤二核苷酸（ＮＡＤＨ）的电化学氧化具有明显的催化作用。可使ＮＡＤＨ     

铂、钌共修饰碳纳米管电极的制备及对甲醇的电催化氧化

碳纳米管以其独特的结构,良好的电性能和机械性能吸引了众多的关注~([1]),被认为是潜在的异相催化剂载体 ~([2]).近来关于碳纳米管负载催化剂的合成及其在异相催化中应用的研究已见报道~([3]).     

碳纳米管修饰电极对多巴胺和抗坏血酸的电催化氧化

研究了碳纳米管修饰玻碳电极 (NTCME)的制备方法及对多巴胺 (DA)和抗坏血酸 (AA)的电催化氧化作用。在磷酸盐缓冲溶液 (PBSpH 7.4)中 ,以NTCME为工作电极时 ,DA与AA的氧化电位分别为 0 .2 6和 0 .0 1V(vs.SCE) ,比在裸玻碳电极 (GC)上分别降低了 0 .0 7和 0 .6 2V。NTCME能消除DA与AA共存时测定的相互干扰。利用二阶导数卷积伏安法测定 ,DA与AA分别在 2 .0 0× 10 - 6～ 3.84× 10 - 4 和 7.99× 10 - 5～ 3.6 6× 10 - 3 mol L浓度范围内 ,峰高与浓度呈线性关系 ;检出限分别为 1.90× 10 - 7和 5 .96× 10 - 5mol L。     

天青Ⅰ修饰玻碳电极的电化学性质及其对NADH的催化氧化

本文利用滴涂于玻碳表面的Nafion膜中负电性的磺酸基与天青I阳离子之间的静电作用,以实现天青I的固定化,从而制备出Nafion/天青I电催化型烟酰胺腺嘌呤二核苷酸(NADH)传感器。采用循环伏安法考察了传感器的电化学性质,并研究了该修饰电极对NADH的电催化作用。实验结果表明:该修饰电极对NADH有良好的电催化作用,NADH氧化峰电位比未修饰的玻碳电极负移了660 mV,响应电流与NADH的浓度在8.7×10-5~1.5×10-2mol/L范围内呈良好的线性关系。该方法检出限为3.0×10-5mol/L。     

碳纳米管修饰电极上沙丁胺醇电催化氧化研究

将多壁碳纳米管(MWNT)分散在疏水性表面活性剂双十六烷基磷酸(DHP)溶液中形成稳定、均相的分散液,然后制备多壁碳纳米管-DHP复合膜修饰玻碳电极(MWNT-DHP/GCE).应用方波伏安法研究了沙丁胺醇在修饰电极上的电化学行为,结果表明,碳纳米管复合膜修饰电极对沙丁胺醇的氧化有良好的电催化活性,其氧化反应为一电子一质子过程,氧化电位比裸玻碳电极负移40 mV,峰电流增加了4.5倍.在最佳测试条件下,氧化峰电流与沙丁胺醇浓度在8.3×10-7~3.3×10-6mol/L范围内呈良好线性关系,开路富集2min,检出限达1.8×10-7mol/L.该修饰电极具有良好的重现性、稳定性.     

硫堇/Nafion/石墨烯修饰电极对NADH的电催化活性研究

为了提高电化学检测NADH的分析性能,制备了硫堇/Nafion/石墨烯修饰的玻碳电极(GCE),利用Nifion的强离子交换能力将硫堇修饰在电极表面,形成硫堇/Nafion/石墨烯复合电极.与裸玻碳电极相比,在NADH的反应中观察到了电位明显降低和电流响应显著增大.证实了硫堇/Nafion/石墨烯复合电极对NADH有协同的电催化能力.为构造有效地检测NADH的电化学传感器提供一个良好的应用平台.     

碳纳米管电极电催化氧化降解活性艳红X-3B研究

将催化裂解法制得的碳纳米管,先经稀酸分散和空气热氧化处理,再按一定比例加入酚醛树脂,高速球磨处理后,将碳纳米管电极片热压成型.其表面形貌由扫描电镜(SEM)表征.以碳纳米管电催化电极作阳极,不锈钢片为阴极,降解处理含活性艳红X-3B模拟印染废水.考察了电流密度、电解质浓度、体系反应温度及pH值对废水降解效率的影响.结果表明:酸性条件下有利于染料有机物降解反应的进行,于常温下即可作高效降解处理.     

苦参碱在多壁碳纳米管修饰玻碳电极上的电催化氧化及其电分析方法

研究了苦参碱(Matrine, MT) 在多壁碳纳米管修饰玻碳电极(MWCNT/GCE)上的电化学行为. 与GCE相比, MT在MWCNT/GCE上峰电位负移120 mV, 峰电流增大约2.5倍, 表明MWCNT/GCE对MT的电化学氧化具有良好的催化作用. 同时测定并计算了MT在MWCNT/GCE上的电极过程动力学参数: 电子转移系数α、电极反应速率常数ks、扩散系数D. 运用差分脉冲伏安法对苦参碱样品含量进行测定, 相对标准偏差为0.12%～2.9%, 加标回收率为98.4%～99.0%. 该方法可用于MT的电化学定量测定.     

亚硝酸盐在碳纳米管修饰玻碳电极上的电催化氧化及电分析方法研究

用循环伏安法研究了NO2-在多壁碳纳米管修饰玻碳电极(MWCNT/GCE)上的电催化氧化行为.采用计时库仑法(CC)和计时电流法(CA)得到了NO2-在MWCNT/GCE上的动力学参数;利用稳态电流-时间曲线法测定了NO2-电流响应信号与浓度间的关系.结果表明,电流响应信号随其浓度成比例增长,响应时间小于4s,最低响应浓度为2μmol/L.用线性扫描伏安法(LSV)对实际工业废水水样进行了分析测定,相对标准偏差(RSD)小于3%,加标回收率在98%～100%之间.     

多壁碳纳米管修饰电极对核黄素的电催化研究

碳纳米管具有导电性和完整的表面结构，因而它可用作一种良好的电极材料。核黄素（维生素B2，RF）是黄素单核苷酸（FMN）和黄素腺嘌呤二核苷酸（FAD）的组成部分。而FMN和FAD是生命体中重要的辅酶，也是多种重要脱氢酶的辅酶，在线粒体呼吸链中起着传递电子和质子的作用。FMN和FAD分子中传递电子的功能部分与核黄素相同，均为异吡咯嗪环。本文用电化学方法研究了核黄素的电化学性质。     

Electrochemical Polymerization of Azure Blue H and Its Electro-catalytic Activity toward NADH Oxidation

Poly (azure blue II) (PABII) thin film modified electrode was successfully assembled on the surface of a glassy carbon electrode by means of electrochemical polymerization, which was carried out with cyclic voltammetric sweeping in the potential range of ‐ 0.6 to + 1.3 V (vs. SCE) in Britton‐Robinson buffer solution (pH = 9.8) containing 1.25 ± 10–⁴ mol/L azure blue II. The effect of pH on the polymerization process of azure blue II and the electrochemical characteristics of the polymer‐modified electrodes were studied in detail. The experimental results indicated that the electropolymerization of azure blue II could take place in basic or neutral media. The cyclic voltammograms of poly (azure blue II) thin film modified electrode showed the presence of two couples of redox peaks. The film modified electrode exhibited potent and persistent electrocatalysis for oxidation of dihydronicotiamide adenine dinucleotide (NADH) in phosphate buffer media with a diminution of the overpotential of about 410 mV and an increase in peak current. The presence of some divalent cations in an electrolyte can greatly enhance the electrocatalytic current for oxidation of NADH. The electrocatalytic current increased linearly with NADH concentration from 1.0 ± 10–⁵ to 8.0 ± 10–³ mol/L in the presence of 4.0 ± 10–² mol/L Mg²⁺ cation. The detection limit (3s_b1/S) was 5.0 ± 10–⁶ mol/L, and the relative standard deviation of determination results was 4.2% for six successive determinations of 5.0 ± 10–⁴ mol/L NADH in the presence of Mg²⁺ cation.     

6-Vinyl coenzyme Q0: Electropolymerization and electrocatalysis of NADH oxidation exploiting poly-p-quinone-modified electrode surfaces

6-Vinyl coenzyme Q₀ serves as a convenient starting material for the formation of electropolymerized coenzyme Q₀ on glassy carbon electrodes and the modified electrodes displays electrocatalytic activity toward NADH (β-nicotinamide adenine dinucleotide) oxidation. The detection of NADH was measured by differential pulse voltammetry, which reveals that the peak current is linear to the concentration of NADH within the range of 10–100 μM. This would be helpful for the understanding of the interaction between coenzyme Q₀ and NADH in the biological process.     

Electrochemical and solid-phase synthetic modification of glassy carbon electrodes with dihydroxybenzene compounds and the electrocatalytic oxidation of NADH

We report the preparation, using electrochemical and solid-phase synthesis, and characterisation of a 26 member library of 13 dihydroxybenzene derivatives covalently attached to glassy carbon through ethylenediamine (EDA) and C₆H₄CH₂NH linkers. First, Boc-protected EDA or Boc–NHCH₂C₆H₄ were electrochemically attached to the GC surface. After Boc-deprotection, dimethoxybenzoyl chlorides were coupled to the EDA and C₆H₄CH₂NH linkers using solid-phase synthesis followed by deprotection of the methoxy groups to give the corresponding dihydroxybenzene compounds. Surface coverage and electrochemical parameters of the dihydroxybenzene modified electrodes were evaluated in parallel using cyclic voltammetry. The mid-peak potentials, E_mp, and surface coverages for the 13 dihydroxybenzene derivatives were found to be independent of the choice of linker. The mid-peak potentials of the immobilised dihydroxybenzene derivatives varied between 0.0 and 260 mV vs. SCE and their surface coverages varied between 0.07 and 1.1 nmol cm^− 2, depending on the pattern of substitution of the dihydroxybenzene ring. The electrocatalytic activities of the library were evaluated for mediation of NADH oxidation, and the ortho-dihydroxybenzene derivatives were found to have higher catalytic activity.     

Electrocatalytic oxidation of NADH at carbon paste electrodes modified with meldola blue adsorbed on zirconium phosphate: effect of Ca2+ and polyethyleneimine

The basic electrochemistry of carbon paste electrodes modified with Meldola Blue adsorbed on zirconium phosphate (MB-ZP-CPEs) and their ability to oxidize NADH have been investigated. Three types of carbon powder (graphite and glassy carbon-type Sigradur K and G) were used to obtain MB-ZP-CPEs. On comparing cyclic voltammograms recorded at MB-ZP-CPEs, similarly prepared from the three different carbon powders, those made with Sigradur K exhibited the lowest background current, and the best MB electrochemistry, seen as the highest peak intensities and smallest peak separation. Using MB-ZP-CPEs based on Sigradur K a study on NADH oxidation was done focusing on the effect of the Ca²⁺ concentration in the contacting solution and on the addition of polyethyleneimine (PEI) into the paste. It can be stated that MB-ZP-CPEs based on Sigradur K and containing 1.23% (w/w) PEI exhibited the best behavior for NADH oxidation, measured by the highest electrocatalytic rate constant (8.2×10³ M^–1 s^–1).     

多壁碳纳米管/壳聚糖-联吡啶钌复合物修饰的石墨电极上电化学发光行为的研究及分析应用

基于盐酸曲马多对联吡啶钌(Ru(bpy)32+)的电化学发光信号有较强的增敏作用, 建立了一种多壁碳纳米管/壳聚糖-联吡啶钌复合物修饰的石墨电极上电化学发光检测盐酸曲马多的电化学发光新方法. 通过循环伏安扫描结果表明, 多壁碳纳米管表现出极好的电分析活性, 对联吡啶钌具有较好的电催化作用, 并可应用于盐酸曲马多药物的测定. 在最佳实验条件下, 测定曲马多浓度在6.0×10-4～5.0×10-6 mol/L与相对发光强度成线性关系(r=09982), 检出限(S/N=3)为2.0×10-6 mol/L. 连续平行测定曲马多溶液(5.0×11-5 mol/L) 8次, 发光强度的RSD为3.1%.     

Bio-electrocatalysis of NADH and ethanol based on graphene sheets modified electrodes

Characterization and application of graphene sheets modified glassy carbon electrodes (graphene/GC) have been presented for the electrochemical bio-sensing. A probe molecule, potassium ferricyanide is employed to study the electrochemical response at the graphene/GC electrode, which shows better electron transfer than graphite modified (graphite/GC) and bare glassy carbon (GC) electrodes. Based on the highly enhanced electrochemical activity of NADH, alcohol dehydrogenase (ADH) is immobilized on the graphene modified electrode and displays a more desirable analytical performance in the detection of ethanol, compared with graphite/GC or GC based bio-electrodes. It also exhibits good performance of ethanol detection in the real samples. From the results of electrochemical investigation, graphene sheets with a favorable electrochemical activity could be an advanced carbon electrode materials for the design of electrochemical sensors and biosensors.     

Caffeic acid modified glassy carbon electrode for electrocatalytic oxidation of reduced nicotinamide adenine dinucleotide (NADH)

A new modified electrode was prepared by electrodeposition of caffeic acid (CFA) at the surface of an activated glassy carbon electrode. Cyclic voltammetry was used to investigate the redox properties of this electrode at various solution pH values and at various scan rates. The pH dependence of the electrode response was found to be 58.5 mV/pH, which is very close to the expected Nernstian value. The electrode was also employed to study electrocatalytic oxidation of reduced nicotinamide adenine dinucleotide (NADH), using cyclic voltammetry, chronoamperometry and rotating disk voltammetry as diagnostic techniques. It was found that the modified electrode exhibits potent and persistent electrocatalytic properties toward NADH oxidation in phosphate buffer solution (pH 7.0) with a diminution of the overpotential of about 450 mV compared to the process at an unmodified electrode. The electrocatalytic current increases linearly with NADH concentration in the range tested from 0.05 to 1.0 mM. The apparent charge transfer rate constant and transfer coefficient for electron transfer between the electrode surface and immobilized CFA were calculated as 11.2 s⁻¹ and 0.43, respectively. The heterogeneous rate constant for oxidation of NADH at the CFA-modified electrode surface was also determined and found to be about 3 × 10³ M⁻¹ s⁻¹. Finally, the diffusion coefficient of NADH was calculated as 3.24 × 10⁻⁶ cm² s⁻¹ for the experimental conditions, using chronoamperometric results. Received: 6 January 1999 / Accepted: 11 May 1999     

Electrocatalytic oxidation of NADH at glassy carbon electrodes modified with an electropolymerized film of nile blue A

The kinetic parameters for the electrocatalytic oxidation of di-hydronicotiamide adenine dinucleotide (NADH) at glassy carbon electrodes modified with an electropolymerized film of nile blue A (PNB) have been determined based on rotating disk electrode measurements. The rate constant for the chemical reaction between NADH and PNB is strongly influenced by NADH concentration and the pH value of solution, and it decreases with increasing NADH concentration, indicating that the electrocatalytic process proceeds via the formation of an intermediate of charge-transfer complex between NADH and PNB.     

Electrochemical Polymerization of Azure Blue II and Its Electrocatalytic Activity toward NADH Oxidation

IntroductionOver 30 0dehydrogenasesareknowntobedependentonthenicotiamideadeninedinucleotidecoenzymeinitsreduced (NADH )andoxidized (NAD+)forms ,andamonitoringofenzymaticallygeneratedNADHisthebasisforthedevelopmentofbiosensorsfortheselecteddehydro genase .Hence ,thedetectionofthiscoenzymeisimpor tantinbothpracticalanalysisandbiochemicalsynthesis .ThereportedoverpotentialforoxidationofNADHatpH7 0isabout 1 1Vatcarbonand 1 3Vatplatinumelec trodes .1,2 Itisgenerallyacceptedthatthedirecto…     

Strategies for developing NADH detectors based on Meldola Blue and screen-printed electrodes: a comparative study

Three strategies have been compared to produce screen-printed amperometric detectors for NADH: mixing Meldola Blue (MB) in the screen-printing ink, incorporation of MB-Reinecke salt (MBRS) in the graphite ink and electrodeposition of films of MB-derived polymer (poly (MB)) on electrode surface. Following modification of graphite electrodes the mediators displayed values of the formal potential E°′ from −0.129 to −0.160 V vs. Ag/AgCl and pK_as of 5.09-6.02. A second redox couple with E°′=−0.450 V vs. Ag/AgCl was observed in cyclic voltammetry experiments with poly (MB) sensors or with old electrodes obtained according to the other two strategies. Electropolymerisation of MB allowed to achieve the best operational stability and best detection limit, 2×10⁻⁶ M, for amperometric detection of NADH, while the most extended linear range, 1×10⁻⁵-7.5×10⁻⁴ M, corresponds to sensors with MBRS. MB and MBRS electrodes were compared with a similar NADH detector produced by Gwent Electronic Materials, England. Several characteristics of the modified-electrodes induced by the fabrication by screen-printing were also highlighted.