纳米ZnO修饰电极的制备及其对血红蛋白, 细胞色素c的直接电化学研究

A novel electrochemical method as a sensitive and convenient technique for the determination of heme proteins based on their interaction with ZnO nanorods was developed. A ZnO nanorod modified glassy carbon electrode (ZnO/GCE) was prepared and the electrochemical behaviors of heme proteins, such as hemoglobin (HB) and cytochrome c (Cyt-c), on this modified electrode have been studied. The results showed that both HB and Cyt-c could be oxidized on the modified electrode and the oxidation currents were linear to the concentrations of the analytes in aqueous solutions. In addition, the results of flow injection analysis (FIA) further suggested the high stability and reproducibility of the ZnO nanorod modified electrode. So this method can be applied to the determination of HB and Cyt-c in biological systems.     

Photorechargeable Properties of Metal Hydride-SrTiO3 Electrode

A photosensitive metal hydride electrode was prepared by modification with perovskite-type SrTiO3 photocatalyst. The photorechargeable properties of the prepared electrodes were investigated by using electrochemical cyclic voltammetry and EIS measurements. The results showed that the modified electrode exhibited the obvious photorechargeable properties. The reduction current increased remarkably under the xeon light irradiation compared with the unmodified electrode. During the photocharging process, the potential of the modified electrode shifted quickly to negative direction and a potential plateau of about -0.90V (vs. Hg/HgO) occurred at the end of light irradiation. The corresponding discharge capacity of the electrode was about 5.4 mAh/g.     

Direct Electrochemical Evidence of the Dissociation and Adsorption Behavior of Acetonitrile at Gold Electrodes by Ultrafast Voltammetry

Ultrafast cyclic voltammetry was used to study the redox behavior of a gold electrode in acetonitrile. The direct electrochemical evidence of the dissociation and adsorption behavior of acetonitrile at gold electrodes was found. It could be stated that two consecutive redox paths are involved, each with a special adsorption state acting as the reaction intermediate. The mean value, obtained of the electron-transfer rate constant of the second path, was 1.3 × 105 s-1 with a standard deviation of 0.24 × 105 s-1.     

Interaction of Biologically Active Molecules with Sulfur-modified Gold Surface

The immobilization of cytochrome c or horseradish peroxidase at the sulfur-modified gold electrode exhibits a ra-pid electron transfer behavior because of its specific orientation on the electrode surface and the interaction between cytochrome c or horseradish peroxidase and sulfur-modified on the surface of the Au electrode.     

Electrochemical Reduction of Oxygen on Multi-walled Carbon Nanotubes Electrode in Alkaline Solution

The multi-walled carbon nanotubes (MWNTs) electrode was constructed using polytetrafluoroethylene as binder, and the electrochemical reductive behavior of oxygen in alkaline solution was first examined on this electrode. Compared with other carbon materials, MWNTs show higher electrocatalytic activity, and the reversibility of O2 reduction reaction is greatly improved. The experiments reveal that the electrochemical reduction of O2 to HO2 is controlled by adsorption. The preliminary results illustrate the potential application of MWNTs in fuel cells.     

Direct electrochemistry and enzymatic activity of hemoglobin in positively charged colloid Au nanoparticles and hemoglobin layer-by-layer self-assembly films

Alternate adsorption of positively charged colloid-Au nanoparticles (nano-Au⊕) and negatively charged hemoglobin (Hb) on L-cysteine (L-cys) modified gold electrode resulted in the assembly of {Hb/nano-Au⊕}n layer-by-layer films/L-cys modified gold electrode. The nano-Au⊕ was characterized by transmission electron micrograph (TEM) and microelectrophoresis. The modified electrode interface morphology was characterized by electrochemical impedance spectroscopy (EIS), atomic force mi- croscopy (AFM), cyclic voltammograms (CV) and chronoamperometry. Direct electron transfer between hemoglobin and gold electrodes was studied, and the apparent Michaelis-Menten constant ( km app) of the modified electrode was evaluated to be 0.10 mmol·L?1. Moreover, the higher activity of proteins in the nano-Au⊕ films could be retained compared with the electropolymerization membrane, since the pro- teins in nano-Au⊕ films retained their near-native structure. Direct electron transfer between hemoglo- bin and electrode and electrochemically catalyzed reduction of hydrogen peroxide on a modified elec- trode was studied, and the linear range was from 2.1×10-8 to 1.2 ×10?3 mol·L-1 (r = 0.994) with a detection limit of 1.1×10-8 mol·L-1 H2O2.     

Detection of dopamine using self-assembled diazoresin/single-walled carbon nanotube modified electrodes

Ultrathin films of diazoresin(DR)/single-walled carbon nanotube(SWNT) were fabricated on thioglycollic acid(TGA) decorated gold(Au) electrodes by the self-assembly method combined with the photocrosslinlcing technique.The electrochemical behavior of dopamine(DA) at the DR/SWNT modified electrodes was studied using the cyclic voltammetry(CV) and differential pulse voltammetry(DPV) methods.Under the optimal conditions,a linear CV response to DA concentration from 1 μmol/L to 40 μmol/L was observed,and the detection limit of DA was 2.1 ×10~(-3) μmol/L via the DPV method in the presence of 10 μmol/L of uric acid(UA) or 2.5 × 10~(-3) μmol/L via the DPV method in the presence of10 μmol/L of ascorbic acid(AA).Moreover,the modified electrodes exhibited good reproducibility and sensitivity,demonstrating its feasibility for analytical purposes.     

Electrochemical preparation of nickel-iron hydroxide loaded on multi-walled carbon nanotubes electrode for the detection of ureaEI北大核心CSCD

A nickel-iron hydroxide/multi-walled carbon nanotubes MWCNTscomposite film electrode was prepared by electrochemical derivation of metal hexacyanoferrate in alkaline solution. MWCNTs film modified electrode was prepared by dropping methodthen Ni-Fe bimetal hexacyanoferrateNi-FeHCFnanoparticles were deposited on the surface of MWCNTs by cyclic voltammetry. This Ni-FeHCF/MWCNTs electrode was electrochemically derived in alkaline solution and a MWCNTs composite film electrodeNiOH2-FeOH3 /MWCNTs/ CCEwas obtained. The surface morphology and the electrochemical behavior of this modified electrode were characterized by scanning electron microscopeSEMand cyclic voltammetryCV. This electrode exhibited high catalytic activity for the electrochemical oxidation of urea under the synergistic action of each component. Based on thisthe non-enzymatic electrochemical sensing of urea was established. In 1.0 mol/L KOH solution the linear range of urea by amperometry was between 5.0×10−3 and 2.8 mmol/Land the detection limit was 3.6 μµmol/L. The sensitivity to urea was 54.3 μµA/mmol/L. This electrode could be used for the determination of urea in river water and human urine samples. © 2022, Youke Publishing Co.,Ltd. All rights reserved.     

Preparation, Electrochemical Behavior and Electrocatalytic Activity of a Copper Hexacyanoferrate Modified Ceramic Carbon Electrode

A copper hexacyanoferrate modified ceramic carbon electrode （CuHCF/CCE） had been prepared by two-step sol-gel technique and characterized using electrochemical methods. The resulting modified electrode showed a pair of well-defined surface waves in the potential range of 0.40 to 1.0 V with the formal potential of 0.682 V （vs. SCE） in 0.050 mol·dm^-3 HOAc-NaOAc buffer containing 0.30 mol·dm^-3 KCl. The charge transfer coefficient （a） and charge transfer rate constant （ks） for the modified electrode were calculated. The electrocatalytic activity of this modified electrode to hydrazine was also investigated, and chronoamperometry was exploited to conveniently determine the diffusion coefficient （D） of hydrazine in solution and the catalytic rate constant （kcat）. Finally, hydrazine was determined with amperometry using the resulting modified electrode. The calibration plot for hydrazine determination was linear in 3.0 × 10^-6--7.5 × 10^-4 mol·dm^-3 with the detection limit of 8.0 × 10^-7 molodm^-3. This modified electrode had some advantages over the modified film electrodes constructed by the conventional methods, such as renewable surface, good long-term stability, excellent catalytic activity and short response time to hydrazine.     

Glucose biosensor based on new carbon nanotube-gold-titania nano-composites modified glassy carbon electrode

In this paper, a novel biosensor was prepared by immobilizing glucose oxidase （GOx） on carbon nanotube-gold-titania nanocomposites （CNT/Au/TiO2） modified glassy carbon electrode （GCE）. SEM was initially used to investigate the surface morphology of CNT/Au/TiO2 nanocomposites modified GCE, indicating the formation of the nano-porous structure which could readily facilitate the attachment of GOx on the electrode surface. Cyclic voltammogram （CV） and electrochemical impedance spectrum （EIS） were further utilized to explore relevant electrochemical activity on CNT]Au/TiO2 nanocomposites modified GCE. The observations demonstrated that the immobilized GOx could efficiently execute its bioelectrocatalytic activity for the oxidation of glucose. The biosensor exhibited a wider linearity range from 0.1 mmol L-1 to 8 mmol L^-1 glucose with a detection limit of 0.077 mmol L^- 1.     

Atomic Force Microscopic and Electrochemical Investigations of an Electrostatically Fabricated Single‐Wall Carbon Nanotubes Modified Electrode

Single‐wall carbon nanotubes (SWNTs) sub‐monolayer film has been prepared by simply electrostatically adsorbing nanotubes onto a 2‐aminoethanethiol self‐assembled monolayer (SAM) on a gold bead electrode. Tapping‐mode atomic force microscopy (TM‐AFM) is used to characterize the SWNT film, which exhibits that the orientation of SWNTs on the SAM is horizontal and the surface coverage is quite low. The SWNTs modified electrode shows nearly ideal electrochemical response to Fe(CN) /Fe(CN) redox probe. The electrode with such a low SWNTs coverage, however, shows good electrocatalytic behavior to cytochrome c.     

Electrochemical and conductivity measurements of single-wall carbon nanotube network electrodes

The electrochemical response of two-dimensional networks of pristine single-wall carbon nanotubes (SWNTs) has been investigated. SWNTs were grown by catalyzed chemical vapor deposition on an insulating SiO2 substrate, and then electrically contacted by lithographically defined Au electrodes. Subsequent insulation of the contact electrodes enabled the electrochemical properties of the SWNT network to be isolated and directly studied for the first time. The electrochemical activity of the SWNT network was found to be strongly dependent on the applied potential. For the same SWNT electrode, the limiting current for the oxidation of 5 mM Fe(phen)32+ was found to be much greater than expected based on the signal for the reduction of 5 mM Ru(NH3)63+. Simultaneous conductance and electrochemical measurements demonstrated decreasing conductance as the potential was scanned negative (versus Ag/AgCl) with the minimum conductance at around the reduction potential for Ru(NH3)63+. These results are consistent with the presence of both metallic and semiconducting SWNTs in the SWNT network electrode. Moreover, these results show that through appropriate choice of mediator and electrode potential, metallic SWNTs can be electrochemically addressed independently of semiconducting SWNTs.     

Al Electrode Modified by Au Atoms as a Novel Electrode for Electrocatalytic Oxidation of Thiosulfate

An aluminum electrode modified with gold atoms was introduced as a novel electrode. Gold atoms were deposited both chemically and electrochemically onto the aluminum electrode to make an aluminum/gold (Al/Au) modified electrode (ME). The experimental results showed that the Al/Au modified electrode prepared by chemical deposition, exhibits much more current than the electrochemical deposition method. The electrochemical behavior of the Al/Au modified electrode was studied by cyclic voltammometry. This modified electrode showed two pairs of peaks, a₁c₁ and a₂c₂, with surface‐confined characteristics in a 0.5 M phosphate buffer. The dependence of E_pa of the second peak (a₂c₂) on pH shows a Nernestian behavior with a slope of 55 mV per unit pH. The effect of different supporting electrolytes, solution's pH and different scan rates on electrochemical behavior of Al/Au modified electrode was studied. Au deposited electrochemically on a Pt electrode (Pt/Au) was also used as another modified electrode. A comparative study of electrochemical behavior of bare Al, Pt/Au and Al/Au modified electrodes showed that both Pt/Au and Al/Au electrodes have the ability of electrocatalytic oxidation of S₂O₃^2?, but the electrocatalytic oxidation on the latter was better than the former. The kinetics of the catalytic reaction was investigated by using cyclic voltammetry and chronoamperometry techniques. The average value of the rate constant for the catalytic reaction and the diffusion coefficient were evaluated by means of chronoamperometry technique.     

Electrochemistry at chemically assembled single-wall carbon nanotube arrays

Single-wall carbon nanotubes (SWNTs) chemically assembled on gold substrates were employed as electrodes to investigate the charge transfer process between SWNTs and the underlying substrates. Cyclic voltammetry (CV) indicates that the assembled SWNTs allow electron communication between a gold electrode and the redox couple in solution, though the SWNTs are linked directly onto the insulating monolayer of 11-amino-n-undecanethiol (AUT) on the Au substrate. An electron transfer (ET) mechanism, which contains an electron tunneling process across the AUT monolayer, is proposed to explain the CV behavior of Au/AUT/SWNT electrodes. Electrochemical measurements show that the apparent electron tunneling resistance, which depends on the surface density of assembled SWNTs, has apparent effects similar to those of solution resistance on CV behavior . The theory of solution resistance is used to describe the apparent tunneling resistance. The experimental results of the dependence of ET parameter psi on the potential scan rate upsilon are in good agreement with the theoretical predictions. Kinetic studies of the chemical assembly of SWNTs by atomic force microscopic (AFM), electrochemical, and Raman spectroscopic methods reveal that two distinct assembly kinetics exist: a relatively fast step that is dominated by the surface reaction, and a successive slow step that is governed by bundle formation.     

Fabrication,Characterization, and Application of ‘Sandwich‐Type’ Electrode Based on Single‐Walled Carbon Nanotubes and Room Temperature Ionic Liquid

The much‐enhanced electrochemical responses of potassium ferricyanide and methylene blue (MB) were firstly explored at the glassy carbon electrode modified with single‐walled carbon nanotubes (SWNT/GCE), indicating the distinct electrochemical activity of SWNTs towards electroactive molecules. A hydrophobic room temperature ionic liquid (RTIL), 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF₆), was used as electrode modification material, which presented wide electrochemical windows, proton permeation and selective extraction ability. In consideration with the advantages of SWNTs and RTIL in detecting target molecules (TMs), a novel strategy of ‘sandwich–type’ electrode was established with TMs confined by RTIL between the SWNT/GCE and the RTIL membrane. The strategy was used for electrochemical detection of ascorbic acid (AA) and dopamine (DA), and detection limits of 400 and 80 fmol could be obtained, respectively. The selective detection of DA in the presence of high amount of AA could also be realized. This protocol presented many attractive advantages towards voltammetric detection of TMs, such as low sample demand, low cost, high sensitivity, and good stability.     

Detection of Thiols by o‐Quinone Nanocomposite Modified Electrodes

A chemically modified glassy carbon (GC) electrode was developed as an amperometric sensor for detection of biological thiols. The electrode was modified by inclusion of co‐enzyme pyrroloquinoline quinone (PQQ) and a co‐catalyst of oxidized single wall carbon nanotubes (Ox‐SWNT) into a gold polypyrrole (Au‐PPy) nanocomposite matrix. The electrode (PQQ/Ox‐SWNT/Au‐PPy/GC) was characterized using scanning electron microscopy and cyclic voltammetry. Optimal conditions for the PQQ/Ox‐SWNT/Au‐PPy/GC electrode were determined and then utilized for the amperometric detection of L‐cysteine, N‐acetyl‐L‐cysteine, L‐penicillamine and D, L‐glutathione. The electrochemical response for each thiol in pH 3.2 citrate phosphate buffer at +450 mV (vs. Ag/AgCl) was found to be linear with limit of detections (LOD, S/N=3) ranging from 0.50 µM for L‐penicillamine to 1.55 µM for D, L‐glutathione with sensitivities of 30.2 nA/µM and 3.6 nA/µM respectively. The electrode design is simple and easy to construct using a minimum amount of co‐enzyme and co‐catalyst, resulting in detection methods with very good stability and improved sensitivity for thiol detection.     

New Multifunctional Porous Materials Based on Inorganic–Organic Hybrid Single‐Walled Carbon Nanotubes: Gas Storage and High‐Sensitive Detection of Pesticides

Single‐walled carbon nanotubes (SWNTs) that are covalently functionalized with benzoic acid (SWNT‐PhCOOH) can be integrated with transition‐metal ions to form 3D porous inorganic–organic hybrid frameworks (SWNT‐Zn). In particular, N₂‐adsorption analysis shows that the BET surface area increases notably from 645.3 to 1209.9 m² g^?1 for SWNTs and SWNT‐Zn, respectively. This remarkable enhancement in the surface area of SWNT‐Zn is presumably due to the microporous motifs from benzoates coordinated to intercalated zinc ions between the functionalized SWNTs; this assignment was also corroborated by NLDFT pore‐size distributions. In addition, the excess‐H₂‐uptake maximum of SWNT‐Zn reaches about 3.1 wt. % (12 bar, 77 K), which is almost three times that of the original SWNTs (1.2 wt. % at 12 bar, 77 K). Owing to its inherent conductivity and pore structure, as well as good dispersibility, SWNT‐Zn is an effective candidate as a sensitive electrochemical stripping voltammetric sensor for organophosphate pesticides (OPs): By using solid‐phase extraction (SPE) with SWNT‐Zn‐modified glassy carbon electrode, the detection limit of methyl parathion (MP) is 2.3 ng mL^?1.     

细胞色素c在硒代胱氨酸修饰电极上的直接电化学

采用电化学和接触角实验方法研究了硒代胱氨酸自组装膜修饰金电极(SeCys SAMs/Au)和十六烷基三甲基溴化铵(CTAB)-硒代胱氨酸自组装复合膜修饰金电极(CTAB-SeCys SAMs/Au)的特性. 探讨了细胞色素c(Cyt c)在SeCys SAMs/Au电极和CTAB-SeCys SAMs/Au电极上的电化学行为. 实验证明SeCys可促进Cyt c在电极上的氧化还原反应, 加入CTAB后其与SeCys之间的协同作用可在Cyt c与电极之间形成一个开放的通道, 促进作用更加明显, 且在一定浓度范围内, 随CTAB浓度(1×10^-5-1×10^-4 mol·L^-1)的增大, Cyt c在CTAB-SeCys SAMs/Au电极上的氧化还原电流增大, 在接近临界胶束浓度处出现极大值. 在CTAB-SeCys SAMs/Au电极上Cyt c产生一对氧化还原峰, 其峰电位分别为0.305和0.235 V, 其电化学过程受扩散控制. 光谱实验证实SeCys对Cyt c电化学过程的促进作用是由于SeCys与Cyt c中赖氨酸残基的结合.     

Evaluation of Meldola Blue‐Carbon Nanotube‐Sol‐Gel Composite for Electrochemical NADH Sensors and Their Application for Lactate Dehydrogenase‐Based Biosensors

A novel MB‐SWNT‐sol‐gel nanocomposite material was prepared by the sol‐gel process incorporating a redox mediator and carbon nanotubes. The electrocatalytic properties of the nanomaterial based sensor toward NADH oxidation were studied by electrochemical measurements. Significant enhancement of oxidation current is obtained at electrodes modified by MB‐SWNT‐sol‐gel in comparison with the analogous carbon black and/or graphite composite modified electrode. The usefulness of the nanocomposite material as a matrix for immobilizing enzymes is also demonstrated. Analytical parameters of D ‐lactate biosensors with and without SWNT in the hybrid film were compared demonstrating that performance of the biosensor was significantly improved when introducing SWNT.     

Electrodeposition of dendritic gold/silver nanaoparticles on disposable screen‐printed carbon electrode and its application of 4‐mercaptopyridine in in situ electrochemical surface‐enhanced Raman scattering

Column electrodes pretreated through oxidation–reduction cycles were traditionally used in electrochemical surface‐enhanced Raman scattering (SERS). In this study, a disposable screen‐printed carbon electrode was introduced into in situ electrochemical SERS through the electrodeposition of dendritic gold/silver nanoparticles (Au/AgNPs) onto the surface of the carbon working electrode to induce the SERS enhancement effect on the electrode. Scanning electron microscopy images showed that dendritic Au/AgNPs nanostructures could be fabricated under appropriate electrodeposition conditions and could present a minimum SERS factor of 4.25 × 10⁵. Furthermore, the absorbed behavior of 4‐mercaptopyridine was investigated under different potentials. The adsorption configuration was inferred to transform from ‘vertical’ to ‘lying‐flat’. The proposed new electrode combined with a portable Raman spectrometer could be useful in the identifying products or intermediates during electrochemical synthesis or electrochemical catalysis in in situ electrochemical SERS. Copyright © 2016 John Wiley & Sons, Ltd.