聚甲苯胺蓝-(多壁碳纳米管/PDDA)_n杂化膜修饰印刷电极的制备及其对NADH的测定

利用静电层层组装的方式在印刷电极表面制备了(多壁碳纳米管/邻苯二甲酸二乙二醇二丙烯酸酯(PDDA))n多层膜,采用电位扫描电聚合法在修饰有多层膜的印刷电极表面聚合甲苯胺蓝,制备了聚甲苯胺蓝-(多壁碳纳米管/PDDA)n杂化膜修饰电极。扫描电镜实验表明,多壁碳纳米管均匀分布在杂化膜中,且多壁碳纳米管的掺杂使杂化膜表现出明显的多孔性。电化学实验表明,杂化膜具有良好的导电性且多壁碳纳米管的掺杂显著增加了聚甲苯胺蓝在电极表面的担载量,提高了检测灵敏度。在pH7.4的磷酸盐缓冲液中,杂化膜修饰电极对β-烟酰胺腺嘌呤二核苷酸(NADH)的氧化具有良好的催化作用,与裸电极相比氧化电位降低了560 mV,灵敏度明显提高。在8.7×10-8~1.3×10-4mol/L范围内,NADH的浓度与氧化电流呈线性关系,检出限为2.8×10-8mol/L,该修饰电极可用于NADH的测定。     

六氰合铁酸铜钴-多壁碳纳米管修饰电极研究

采用电沉积方法制备六氰合铁酸铜钴-多壁碳纳米管复合修饰电极(CuCoHCF-MWCNTs/GCE).研究碳纳米管用量、电解液组成对该修饰电极性能的影响.结果表明,与单一的六氰合铁酸铜钴薄膜修饰电极相比,六氰合铁酸铜钴-多壁碳纳米管复合修饰电极具有更优良的电化学特性,以其催化氧化过氧化氢,峰电流与过氧化氢浓度在3.16×10-5～2.92×10-3mol·L-1范围内呈良好的线性关系,线性回归方程为ip(μA)=0.5529+1.1299C(×10-4mol·L-1),相关系数r=0.9966,检出限为1.75×10-5mol·L-1.     

Electrochemical Behaviour of Microwave‐assisted Oxidized MWCNTs Based Disposable Electrodes: Proposal of a NADH Electrochemical Sensor

The effect of the oxidation degree of multiwalled carbon nanotubes (MWCNTs) for the detection of NADH was evaluated in this paper. MWCNTs were oxidized by microwave‐assisted sulfonitic treatment at different times (5, 10, 15, and 30 min) and deposited onto a graphite screen printed electrodes. Oxidized MWCNTs were characterized and the electrochemical performance evaluated. The best sensor in terms of sensitivity and stability was obtained after 15 minutes of oxidation (SPE/CNT15). A significant reduction of the NADH oxidation potential was recorded for oxidized MWCNTs compared with unmodified MWCNTs (0.270 V and 0.500 V, respectively vs. Ag/AgCl pseudo reference electrode), increasing the selectivity of the system. Chronoamperometric calibration curves carried out applying a potential of 0.3 V for 1 min were linear in the 4–35 μM range of NADH. A limit of detection of 1 μM was achieved with negligible surface fouling (three consecutive calibration curves, 30 total measurements: slope decrease 5.9 %). Inter electrode reproducibility (n=13) was good resulting in RSD of 15.2 % and 5.0 % for the peak intensity and the oxidation potential, respectively. Quantification of glucose in white wine samples was carried out to demonstrate the ability of the NADH sensor to work in real samples. A good correlation with a spectrophotometric kit for the glucose quantification was achieved.     

Electrochemical biosensors based on redox carbon nanotubes prepared by noncovalent functionalization with 1,10-phenanthroline-5,6-dione

To improve the electrocatalytic activities of carbon nanotubes (CNT) towards the oxidation of nicotinamide adenine dinucleotide (NADH), we derive them with a redox mediator, 1,10-phenanthroline-5,6-dione (PD), by the noncovalent functionalization method. The redox carbon nanotubes (PD/CNT/GC) show excellent electrocatalytic activities towards the oxidation of NADH (catalytic reaction rate constant, k(h) = 7.26 × 10(3) M(-1) s(-1)), so the determination of NADH can be achieved with a high sensitivity of 8.77 μA mM(-1) under the potential of 0.0 V with minimal interference. We also develop an amperometric ethanol biosensor by integration of alcohol dehydrogenase (ADH) within the redox carbon nanotubes (PD/CNT/GC). The ethanol biosensor exhibits a wide linear range up to 7 mM with a lower detection limit of 0.30 mM as well as a high sensitivity of 10.85 nA mM(-1).     

Low Potential Detection of NADH at Titanium‐Containing MCM‐41 Modified Glassy Carbon Electrode

Titanium‐containing MCM‐41 (Ti‐MCM‐41) modified glassy carbon electrode (GCE) can exhibit an excellent electrocatalytic activity towards the oxidation of β‐Nicotinamide adenine dinucleotide (NADH). A dramatic decrease in the over‐voltage of NADH oxidation reaction is observed at 0.28 V (vs. SCE). The modified electrode is found to be stable and reproducible. The electrode shows a linear response for a wide range of 10–1200 μM NADH and the detection limit is 8.0 μM. Ti‐MCM‐41 mesoporous molecular sieves provide an efficient matrix for development of NADH biosensors and the prepared electrode not only can be used to detect the concentration of NADH in biochemical reaction, but also as the potential matrix of the construction of dehydrogenases biosensor.     

Graphene-carbon nanotubes modified graphite electrode for the determination of nicotinamide adenine dinucleotide and fabrication of alcohol biosensor

Through layer-by-layer adsorption (LBL) technique, the positively charged multiwalled carbon nanotubes (MWCNTs) and negatively charged graphene multilayer film were formed on graphite-poly(diallyldimethylammoniumchloride)-polystyrenesulphonate (Gr/PDDA/PSS) modified electrode. Due to large surface area and remarkable electrocatalytic properties of MWCNTs and graphene, the Gr/(PDDA/PSS-[MWCNTs-NH ₃ ⁺ -graphene-COO^?]₅) electrode exhibits potent electrocatalytic activity towards the electro-oxidation of nicotinamide adenine dinucleotide (NADH). A substantial decrease in the overpotential was observed at modified electrode, and the electrode showed high sensitivity to the electrocatalytic oxidation of NADH. The modified electrode was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The diffusion coefficient was calculated by chronocoulometry. Chronoamperometric studies showed the linear relationship between oxidation peak current and the concentration of NADH in the range 25–250?μM (R?=?0.999) with the detection limit of 0.1?μM (S/N?=?3). Further, dopamine, uric acid, acetaminophen and hydrogen peroxide do not interfere in the detection of NADH. The ability of MWCNTs and graphene to promote the electron transfer between NADH and the electrode exhibits a promising biocompatible platform for development of dehydrogenase-based amperometric biosensors. Alcohol dehydrogenase (ADH) was casted on Gr/(PDDA/PSS-[MWCNTs-NH ₃ ⁺ -graphene-COO^?]₅) electrode; the resulting biosensor showed rapid and high sensitive amperometric response to ethanol with the detection limit of 10?μM (S/N?=?3).     

In situ Electroreduction of Graphene Oxide: Increased Sensitivity for the Determination of NADH

A novel and useful method to catalyze the electro‐oxidation of nicotinamide adenine dinucleotide (NADH) over a glassy carbon electrode (GCE) modified with graphene oxide (GO) is presented. Based on the presence of oxygen moieties in GO, which can be easily reduced, an in situ electrochemical generation of reduced graphene oxide (denoted as erGO) applying a sufficient negative potential. A potential of ?1.000 V was selected to generate the erGO/GCE as a pretreatment potential before the detection of NADH. The in situ generated erGO/GCE system produces a decrease in the overpotential of NADH oxidation from +0.720 V to +0.230 V compared with GCE. The process also produced an important increase in current signals. The modified electrode was characterized by scanning electron (SEM) and electrochemical microscopies (SECM), cyclic voltammetry and by Raman spectroscopy. Amperometric detection of NADH via this straightforward electrocatalytic method provides a wide linear range between 10 and 100 μM, a lower detection limit of 0.36 μM and an excellent sensitivity of (1.47±0.09) μA mM^?1.     

碳纳米管负载纳米金-石墨烯量子点修饰电极电化学检测过氧化氢

采用过氧化氢刻蚀法制备石墨烯量子点(GQDs),再采用原位化学还原法制备金纳米粒子-石墨烯量子点纳米复合物(Au NPs-GQDs),最后以聚二甲基二烯丙基氯化铵(PDDA)为交联剂将上述纳米复合物组装于多壁碳纳米管表面,制得金纳米粒子-石墨烯量子点-PDDA-多壁碳纳米管复合材料(Au NPs-GQDsPDDA-MWCNTs)。通过荧光光谱法、紫外-可见吸收光谱法和透射电子显微镜对上述复合材料进行表征。采用滴涂法制得该复合材料修饰的玻碳电极,研究了过氧化氢在该电极上的电化学行为。结果表明:在石墨烯量子点、金纳米粒子和多壁碳纳米管三者的协同作用下,该电极对过氧化氢的电氧化表现出强的催化活性。在优化条件下,安培法检测H_2O_2的线性范围为2.0×10~(-8)~1.5×10~(-3)mol/L,检出限(3sb)为8.0×10~(-9)mol/L,灵敏度为61.6μA/(mmol·L~(-1))。     

血红蛋白在壳聚糖修饰碳纳米管上的电化学特性及对过氧化氢的电催化分析

用壳聚糖对多壁碳纳米管进行修饰,构建了一种用于固定血红蛋白的新型复合材料,并研究了血红蛋白在该碳纳米管上的电化学性质及其对过氧化氢的电催化活性.扫描电镜结果表明,壳聚糖修饰的多壁碳纳米管呈单一的纳米管状,并能均匀分散在玻碳电极表面.紫外光谱分析表明血红蛋白在该复合膜内能很好地保持其原有的二级结构.将该材料固定在玻碳电极上后,血红蛋白能成功地实现其直接电化学.根据峰电位差随着扫描的变化,计算得到血红蛋白在壳聚糖修饰的碳纳米管膜上的电荷转移系数为0.57,表观电子转移速率常数为7.02 s-1.同时,该电极对过氧化氢显示出良好的催化性能,电流响应信号与H2O2浓度在1.0×10-6 ～1.5×10-3 mol/L间呈线性关系,检出限为5.0×10-7 mol/L.修饰电极显示了良好的稳定性.     

Electrocatalytic reaction of hydrogen peroxide and NADH based on poly(neutral red) and FAD hybrid film

A simple method to immobilize poly(neutral red) (PNR) and flavin adenine dinucleotide (FAD) hybrid film (PNR/FAD) by cyclic voltammetry is proposed. The PNR/FAD hybrid film can be easily prepared on an electrode surface involving electropolymerization of neutral red (NR) monomers and the electrostatic interaction between the positively charged PNR and the negatively charged FAD. It exhibits electroactive, stable, surface-confined, pH-dependent, nano-sized, and compatible properties. It provides good electrocatalytic properties to various species. It shows a sensitivity of 5.4 μA mM(-1) cm(-2) and 21.5 μA mM(-1) cm(-2) for hydrogen peroxide (H(2)O(2)) and nicotinamide adenine dinucleotide (NADH) with the linear range of 0.1 μM-39 mM and 5 × 10(-5) to 2.5 × 10(-4) M, respectively. It shows another linear range of 48.8-355.5 mM with the sensitivity of 12.3 μA mM(-1) cm(-2) for H(2)O(2). In particular, the PNR/FAD hybrid film has potential to replace some hemoproteins to be a cathode of biofuel cells and provide the biosensing system for glucose and ethanol.     

Electroanalytical determination of acetaminophen using nano-TiO(2)/polymer coated electrode in the presence of dopamine

We report a new method for selective determination of acetaminophen (AP) in physiological condition. A new hybrid film modified electrode was fabricated using inorganic semiconducting nano-TiO(2) particles and redox active polymer. Redox polymer, poly(acid yellow 9) (PAY) was electrochemically deposited onto nano-TiO(2) coated glassy carbon (GC) electrode. Surface characterizations of modified electrode were investigated by using atomic force microscope and scanning electron microscope. The PAY/nano-TiO(2)/GC hybrid electrode shows stable redox response in the pH range 1-12 and exhibited excellent electrocatalytic activities towards AP in 0.1M phosphate buffer solution (pH 7.0). Consequently, a simple and sensitive electroanalytical method was developed for the determination of AP. The oxidation peak current was proportional to the concentration of acetaminophen from 1.2 x 10(-5) to 1.20 x 10(-4)M and the detection limit was found to be 2.0 x 10(-6)M (S/N=3). Possible interferences were tested and evaluated that it could be possible to selective detection of AP in the presences of dopamine, nicotinamide adenine dinucleotide (NADH), ascorbic acid and uric acid. The proposed method was used to detect acetaminophen in commercial drugs and the obtained results are satisfactory.     

Detection of NADH and Ethanol at Titanium Containing MCM‐41 with Low Overpotential

Titanium‐containing MCM‐41 (Ti‐MCM‐41) modified glassy carbon electrode (GCE) can exhibit an excellent electrocatalytic activity towards the oxidation of β‐Nicotinamide adenine dinucleotide (NADH). A dramatic decrease in the overvoltage of NADH oxidation reaction is observed at 0.28 V vs. SCE. The application in the amperometric biosensing of ethanol using alcohol dehydrogenase enzyme (ADH) also has been demonstrated with this material. The proposed sensor shows a highly sensitivity, an acceptable reproducibility and a good stability. The linear range of ethanol is 25–1000 μM and the detection limit is 8.0 μM. Ti‐MCM‐41 modified electrode not only can be used to detect the concentration of NADH in biochemical reaction, but also as the potential matrix for the construction of dehydrogenases sensor.     

生物分子电催化的研究 Ⅳ: NADH在亚甲绿修饰石墨电极上的电催化氧化

本文以强烈吸附在石墨电极上的亚甲绿作为电子传递媒介体构成修饰电极。在-0.25V～+0.10V电位区间内, 吸附态的亚甲绿表现出相当可逆的氧化还原行为,电极反应有一个电子和一个质子参加。在pH=7.0的磷酸盐缓冲溶液中, 其式量电位E°'为-0.14V, 表观电子传递速率常数K~a~p~p为4.4s^-^1。亚甲绿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的氧化过电位降低500mV, 它作为NADH的电化学安培检测器具有很高的灵敏度和良好的重现性。文中还用X光电子能谱(ESCA)、衰减全反射红外光谱(ATR)等现代分析技术对修饰电极进行了表征。     

A NADH Sensor Based on 1,2‐Naphththoquinone Electropolymerized on Multi‐walled Carbon Nanotubes Modified Glassy Carbon Electrode

A new carbon nanotubes modified electrode (poly‐Nq‐MWCNTs/GCE) was fabricated by electropolymerization of 1,2‐naphththoquinone to the surface of multi‐walled carbon nanotubes modified electrode by casting method. The morphology of the nanocomposite was characterized by scanning electron microscopy. Cyclic voltammetry and chronoamperometry were applied to investigate the electrochemical properties of the poly‐Nq‐MWCNTs nanocomposite modified electrode. The result of electrochemical experiments showed that such modified electrode had a favorable catalytic ability to oxidation of β‐nicotinamide adenine dinucleotide (NADH). The resulted sensor was sensitiveness to NADH and achieved 95β of the steady‐state current within 5s. Furthermore, the anodic peak current was linear to the concentration of NADH for the range from 1.0 μM to 0.14 mM. The linear equation was: I(μA) = 0.3987 + 0.1035c (μmol/L), the correlation coefficient r = 0.9962, the detect limit is down to 1 × 10^?7 M (S/N = 3) and the sensitivity is 0.1035 μA/mmol. The well catalytic activity of the sensor was ascribed to the synergistic effect role played by MWCNTs and poly‐Nq. Moreover, the based sensor possesses good stability and reproducibility.     

Electrocatalytic oxidation of the reduced nicotinamide adenine dinucleotide at carbon ionic liquid electrode modified with polythionine/multi-walled carbon nanotubes composite

A carbon ionic liquid electrode (CILE) was modified with a polythionine (PTh)/multi-walled carbon nanotubes (MWCNTs) composite and used for the detection of reduced nicotinamide adenine dinucleotide (NADH). The electrode was prepared by electrochemical polymerization of thionine on the MWCNTs in neutral medium. Cyclic voltammetry indicated that the electrode was capable of mediating the oxidation of NADH at an overpotential as low as 0.03 V. Amperometric experiments showed that a sensitive and stable response towards NADH is obtained within 5 s. The linear range for the determination of NADH is from 0.8 μmol L^?1 to 422 μmol L^?1, with a detection limit of 0.26 μmol L^?1 (S/N = 3). The wide linear range, lower detection limit and faster response towards NADH suggests that the new method potentially is useful for developing NAD⁺-dependent enzyme-based biosensors.     

阿魏酸聚合修饰玻碳电极的制备及其对NADH的催化氧化

研究了阿魏酸修饰电极的制备、性质及对NADH的电催化作用.该电极在0.1mol/L磷酸缓冲溶液(pH=6.60)中,于-0.1～+0.50V(vs.Ag/AgCl)电位范围内呈现一对氧化还原峰,其式量电位E₀为+0.188V(vs.Ag/AgCl),且E₀随pH增加而负向移动.电子转移系数为0.496,表观电极反应速率常数(ks)为6.6s^-1.电极反应的电子数为1且有1个质子参与.该修饰电极对NADH氧化具有很好的催化作用.在NADH存在下,电极过程由扩散控制,扩散系数为1.76×10^-6cm²/s.NADH浓度在0.01～5.0mmol/L范围内与峰电流呈现良好的线性关系.通过计时安培法测得催化速率常数为6.82×10³mol^-1·L·s^-1.     

Electrocatalysis and Amperometric Detection of the Reduced Form of Nicotinamide Adenine Dinucleotide at Toluidine Blue/Zinc Oxide Coated Electrodes

Thin toluidine blue (TBO) and zinc oxide (ZnO) hybrid films have been grown on glassy carbon electrode (GCE) and indium tin oxide coated (SnO₂) glass electrodes by using cyclic voltammetry (CV). Scanning electron microscopy (SEM) images revealed spherical and beads‐like shape of highly oriented TBO/ZnO hybrid films. Energy dispersive spectrometry (EDS) results declared that the films composed mainly of Zn and O. Moreover, TBO/ZnO hybrid films modified electrode is electrochemically active, dye molecules were not easily leached out from the ZnO matrix and the hybrid films can be considered for potential applications as sensor for amperometric determination of reduced nicotinamide adenine dinucleotide (NADH) at 0.0 V. A linear correlation between electrocatalytic current and NADH concentration was found to be in the range between 25 μM and 100 μM in phosphate buffer. In addition, we observed that dopamine, ascorbic acid and uric acid are not interference in amperometric detection of NADH in this proposed method. In addition, TBO/ZnO hybrid film modified electrode was highly stable and its response to the NADH also remained relentless.     

碳纳米管负载氢氧化镍修饰电极的制备及应用

采用表面滴涂结合循环伏安法制备了碳纳米管负载氢氧化镍修饰电极(Ni(OH)2/MWNT/CCE)。研究了该修饰电极对葡萄糖的电催化氧化性能。结果表明,该修饰电极对葡萄糖具有良好的电催化氧化活性。在优化条件下,安培法检测葡萄糖的线性范围为2.0×10-7～5.7×10-4 mol.L-1(r=0.999 9,s=2 786.5μA.(mmol.L-1)-1.cm-2)和5.7×10-4～2.7×10-3 mol.L-1(r=0.999 1,s=2 005.2μA.(mmol.L-1)-1.cm-2),检出限(3sb)为8.0×10-8 mol.L-1。该法已成功用于血清中葡萄糖含量的测定。     

Mediator-modified electrodes for catalytic NADH oxidation: high rate constants at interesting overpotentials

Carbon paste electrodes were modified with a nitrofluorenone derivative, 2,4,7-trinitro-9-fluorenone, adsorbed on zirconium phosphate (ZP). After electrochemical reduction of the fluorenone derivative, it turns into a very efficient mediator for electrocatalytic NADH oxidation, with a formal potential of about +250 mV vs. Ag/AgCl. The electrochemistry and the electrocatalytic properties of the mediator were investigated with cyclic voltammetry and rotating disk electrode methodology. The second order rate constant with NADH was evaluated and found to be higher than 10(6) M(-1) s(-1), thus approaching true diffusion controlled currents for NADH oxidation.     

A Novel Sensor Based on Carbon Paste Electrode Modified with Polypyrrole/Multi-walled Carbon Nanotubes for the Electrochemical Detection of Cytostatic Drug Rapamycin

The electrocatalytic oxidation of rapamycin, one of the most studied immunosuppressant, cancer-preventing drug, is investigated for the first time on the surface of the modified carbon paste electrode prepared by incorporating multi-walled carbon nanotubes (MWCNTs) and conductive polymer pyrrole using differential pulse voltammetry (DPV). Rapamycin exhibited a well-defined oxidation peak at +1.1 V (versus Ag/AgCl) in Briton Robinson buffer solution with a pH 4.0. Effect of the most important experimental parameters was optimized and obtained signals are linear to the concentration of rapamycin in the range from 0.1 to 20 μM with 0.06 μM limit of detection. The repeatability is calculated as ±2 % and the reproducibility as ±5 %. The possible interfering compounds were tested showing negligible effect and the sensor was successfully applied for the determination of rapamycin in commercial pharmaceutical formulations with obtained recoveries in the range from 98 % to 102 %.