Study of enzyme biosensor based on carbon nanotubes modified electrode for detection of pesticides residue

The paper describes a controllable layer-by-layer （LBL） self-assembly modification technique of multi-walled carbon nanotubes （MWNTs） and poly（diallyldimethylammonium chloride） （PDDA） towards glassy carbon electrode （GCE）, Acetylcholinesterase （ACHE） was immobilized directly to the modified GCE by LBL self-assembly method, the activity value of AChE was detected by using i-t technique based on the modified Ellman method. Then the composition of carbaryl were detected by the enzyme electrode with 0.01U activity value and the detection limit of carbaryl is 10^- 12 g L ^-1 so the enzyme biosensor showed good properties for pesticides residue detection.

Determination of 6-Mercaptopurine in Rat Blood by Microdialysis Coupled with High Performance Liquid Chromatography on a Functionalized Multi-wall Carbon Nanotubes Modified Electrode

A new chemically modified electrode(CME) immobilized on the surface of multi-wall carbon nanotubes functionalized with carboxylic groups was fabricated. The results indicate that the CME exhibits efficiently electrocatalytic oxidation of 6-mercaptopurine(6-MP). The CME can be used as the working electrode in the liquid chromatography for the determination of 6-MP. The peak current of 6-MP is linearly changed with its concentration ranging from 4.0×10 -7 to 1.0×10 -4 mol/L with the calculated detection limit (S/N=3) of 2.0×10 -7 mol/L. Coupled with microdialysis sampling, the method has been successfully applied to assessing the content of 6-MP in rat blood.

Electrooxidation of Nitric Oxide at a Glass Carbon Electrode Modified with Functionalized Single-walled Carbon Nanotube

The electrocatalytic oxidation of nitric oxide（NO） at a glass carbon electrode（GC） modified with functionalized single-walled carbon nanotubes（SWCNTs） was investigated by cyclic voltammetry（CV） and electrochemical impedance spectroscopy（EIS）.It was found that the SWCNT modified electrode could speed greatly up the electron transfer rate compared with the bare GC electrode.After the SWCNT was treated with alkali or mixed acids,the reaction rate and activation energy of NO electrooxidation were changed to different extent.Chemical modification of the SWCNT surface is one of the most powerful methods to change the sensitivity of NO electrooxidation reaction.The modified electrode with SWCNT obtained by the firstly alkali treatment and then the mixed acids treatment was the best one for NO electrooxidation,the result of CV was also confirmed by that of EIS.The anodic processes of NO were recognized more clearly by exploring the reaction mechanism of NO electrooxidation at the SWCNT modified electrode.

Glassy carbon electrode modified with multi-walled carbon nanotubes sensor for the quantihication of antihistamine drug pheniramine in solubilized systems

A sensitive electroanalytical method for quantification of pheniramine in pharmaceutical formulation has been investigated on the basis of the enhanced electrochemical response at glassy carbon electrode modified with multi-walled carbon nanotubes in the presence of sodium lauryl sulfate.The experimental results suggest that the phcniramine in anionic surfactant solution exhibits electrocatalytic effect resulting in a marked enhancement of the peak current response.Peak current response is linearly dependent on the concentration of pheniramine in the range 200-1500 μg/mL with correlation coefficient 0.9987.The limit of detection is 58.31 μg/m L.The modified electrode shows good sensitivity and repeatability.

Sensitive voltammetric determination of xanthinol nicotinate at a carbon nanotubes-ionic liquid gel modified electrode

The electrochemistry of xanthinol nicotinate （Xan） was studied by cyclic voltammetry at a glassy carbon electrode modified by a gel containing multi-walled carbon nanotubes （MWNTs） and room-temperature ionic liquid of 1-butyl-3-methylimidazolium hexafluorophosphate （BMIMPF6）. The modified electrode exhibited good promotion to the electrochemical oxidation of Xan and an ultrasensitive electrochemical method was proposed for the determination of Xan. This method was successfully applied to the determination of Xan in Xan tablets. C 2009 XiaoYu Bao. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Voltammetric Response of Epinephrine at Carbon Nanotube Modified Glassy Carbon Electrode and Activated Glassy Carbon Electrode

The electrochemical behavior of epinephrine at activated glassy carbon electrode and carbon nanotube-coated glassy carbon electrode was studied. Epinephrine could exhibit an anodic peak at about 0.2 V （vs. SCE） at bare glassy carbon electrode, but it was very small. However, when the electrode was activated at certain potential （i.e. 1.9 V） or modified with carbon nanotube, the peak became more sensitive, resulting from the increase in electrode area in addition to the electrostatic attraction. Under the selected conditions, the anodic peak current was linear to epinephrine concentration in the range of 3.3×10^-7 - 1.1×10^-5 mol/L at activated glassy carbon electrode and in the range of 1.0×10^-5 - 5.0×10^-5 mol/L at carbon nanotube-coated electrode. The correlation coefficients were 0.998 and 0.997, respectively. The determination limit was 1.0×10^-7 mol/L. The two electrodes have been successfully applied for the determination of epinephrine in adrenaline hydrochloride injection with recovery of 95%-104%.

Direct Electrochemistry of Catalase on Single Wall Carbon Nanotubes Modified Glassy Carbon Electrode

Direct electrochemistry of catalase (Ct) has been studied on single wall carbon nanotubes (SWNTs) modified glassy carbon (GC) electrode. A pair of well-defined nearly reversible redox peaks is given at –0.48 V (vs. SCE) in 0.1 mol/L phosphate solution (pH 7.0). The peak current in cyclic voltammogram is proportional to the scan rate. The peak potential of catalase is shifted to more negative value when the pH increases. Catalase can adsorb on the SWNTs modified electrode.

Flow Injection Amperometric Determination of Phenol and Chlorophenols at Single Wall Carbon Nanotube Modified Glassy Carbon Electrode

Single wall carbon nanotube modified glassy carbon electrode (SWCNT/GCE) was used for flow-injection analysis (FIA) for phenolic compounds (phenol (P), 4-chlorophenol (CP), 2,4-dichlorophenol (DCP), 2,4,6-trichlorphenol (TCP) and pentachlorophenol (PCP)). Experimental variables such as the detection potential, flow rate and pH of the carrier solution, 0.1 M sodium acetate, were optimized. Under these conditions, the designed electrode showed a very good performance for the amperometric measurements, with no need to apply a cleaning or pre-treatment procedure. The operational stability was tested with 20 repetitive injections of each analyte and was found to be good. The analytical performance of the SWCNT/GCE electrode under flow through conditions was tested and was found to be impressive. When it is compared with other enzymatic and non-enzymatic sensors, it shows wider dynamic range for the detection of phenolic compounds with low limits of detection. These results suggest that the method is quite useful for monitoring and analyzing phenols and chlorophenols.

Electrocatalytic behaviors of poly acridine orange/multi-walled carbon nanotube modified electrode

In this work, noncovalent functionalization of multiwalled carbon nanotube （MWNT） with acridine orange （AO） by electropolymerization is studied. The obtained composite film is a viable alternate electrode material, non-toxic, chemical inert, not volatile, using to construct modified electrode. The new type modified electrode has both of unique properties of MWNT and poly acridine orange （POAO）, can provide good sensitivity, low limits of detection, good response precision, and superb response stability.

Electrochemical behaviors of lomefloxacin at a single-wall carbon nanotube-modified electrode and its interaction with bovine serum albumin

The electrochemical behaviors of lomefloxacin at a single-wall carbon nanotube-modified glassy carbon electrode have been investigated by cyclic voltammetry.In a Britton-Robinson buffer (pH 4.5),lomefloxacin yields a sensitive and well-defined oxidation peak at ca.1.24 V (vs.SCE) on the modified electrode.Compared with the bare glassy carbon electrode,the oxidation peak current of lomefloxacin significantly increases and the oxidation peak potential positively shifts.Under the optimal conditions,the interaction of lomefloxacin with bovine serum albumin is also investigated.The results indicate that an electrochemically inactive supramolecular complex is formed and the formation of complex between lomefloxacin and bovine serum albumin is an intercalation mechanism.The proposed methods offer a reference for the studies on the biological effects and action mechanism of lomefloxacin with albumins in vivo.

Modification of Carbon Nanotube Powder Microelectrode and Nitrite Reduction

The properties of the carbon nanotube powder microelectrodes (denoted CNTPME) are remarkably altered by anodic pretreatment and preadsorption of mediators. It seems that anodic pretreatment leads the long and tangled carbon nanotubes to be partially cut shorter, resulting in more openings as shown by TEM. Besides, the anodic pretreatment may adjust the hydrophobicity of nanotubes to match with that of Os(bpy)32+. As a result, the real surface area and the ability of adsorbing mediator Os(bpy)32+ of the nanotubes are markedly increased so as to effectively catalyze NO2- reduction in acidic solution.

Study on the supramolecular systems of two basic violets with cyclodextrins by MWNTs/Nafion modified glassy carbon electrode

Abstract The electrochemical properties of two basic violets （methyl violet and ethyl violet） at the MWNTs/Nafion modified glassy carbon electrode were investigated. The redox of the basic violets is two-electron and two-proton process, and methyl violet presents stronger electron transfer capacity than ethyl violet. Meanwhile, the inclusion constants of the two basic violets with five CDs were determined by differential pulse voltammetry （DPV）. The two basic violets and CDs can form 1：1 complexes, The inclusion capacities of the two basic violets follow the same order： CM-β-CD 〉 HP-β-CD 〉 TM-β-CD 〉 DM-β- CD 〉 β-CD. ？2009 Yu Jing Guo. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Promotion of the Direct Electron Transfer of Hemoglobin by the Carbon Nanotube

It is reported that the direct electron transfer of hemoglobin (Hb) can be effectively promoted by carbon nanotubes when Hb was immobilized on the surface of the carbon nanotubes modified electrode. The results indicated that the conversion of Hb-Fe(Ⅲ)/Hb-Fe(Ⅱ) is a one-electron coupled one-proton reaction process. The method presented can be easily extended to study the direct electrochemistry of other proteins or enzymes.

Electrochemical Studies of Cytochrome c on Electrodes Modified by Single-Wall Carbon Nanotubes

Single wall carbon nanotubes (SWNTs) modified gold electrodes were prepared by using two different methods. The electrochemical behavior of cytochrome c on the modified gold electrodes was investigated. The first kind of SWNT modified electrode (noted as SWNT/Au electrode) was prepared by the adsorption of carboxyl terminated SWNTs from DMF dispersion on the gold electrode. The oxidatively processed SWNT tips were covalently modified by coupling with amines (AET) to form amide linkage. Via Au—S chemical bonding, the self assembled monolayer of thiol unctionalized nanotubes on gold surface was fabricated so as to prepare the others SWNT modified electrode (noted as SWNT/AET/Au electrode). It was shown from cyclic voltammetry experiments that cytochrome c exhibited direct electrochemical responses on the both electrodes, but only the current of controlled diffusion existed on the SWNT/Au electrode while both the currents of controlled diffusion and adsorption of cytochrome c occurred on the SWNT/AET/Au electrode. Photoelastic Modulation Infared Reflection Absorption Spectroscopy (PEM IRRAS) and Quartz Crystal Microbalance (QCM) were employed to verify the adsorption of SWNTs on the gold electrodes. The results proved that SWNTs could enhance the direct electron transfer process between the electrodes and redox proteins.

Enhanced Growth and Redox Characteristics of Some Conducting Polymers on Carbon Nanotube Modified Electrodes

1 Results Recent studies on the electrochemistry of a number of active compounds at carbon nanotube electrodes have proved beyond doubt their excellent electrocatalytic properties.Particularly,the advancements accomplished towards the functionalization of carbon nanotubes resulting in their enhanced solubilization in aqueous solutions have helped in the preparation of stable carbon nanotube electrodes.Glassy carbon has been invariably the preferred substrate for casting carbon nanotube electrodes.Such c...

Direct Electrochemical Oxidation of NADPH at a Low Potential on the Carbon Nanotube Modified Glassy Carbon Electrode

NADPH can be directly oxidized on a carbon nanotube modified glassy carbon (CNT/GC) electrode in phosphate buffer solution (pH=6.0) with a diminution of the overpotential of more than 700 mV. The anodic peak currents increase linearly with the increase of concentration of NADPH in the range of 5 x 10(-7) to 1 x 10(-3) mol/L with a detection limit of about 1 x 10-7 mol/L. The CNT/GC electrode exhibits high sensitivity, low potential and stability in detecting NADPH and thus might be used in biosensors to study the electrocatalytic reaction of important dehydrogenase-based biological systems.

Simultaneous determination of nitrophenol isomers at the single-wall carbon nanotube compound conducting polymer film modified electrode

Based on the molecular recognition ability of conductive polymer and the peculiar properties of carbon nanotubes,a novel single wall nanotubes(SWNTs)compound poly(4-aminopyridine)modified electrode(SWNTs/POAPE)is prepared at glass carbon electrode(GCE).The electrochemistry response of nitrophenol isomers is studied at the SWNTs/POAPE.The re-sult indicates that o-,m-and p-nitrophenol are separated entirely at the SWNTs/POAPE interface.The electrode present here can be easily used to determine nitrophenol isomers simultaneously with higher sensitivity.

Electrochemical Reaction Mechanism of Phenacetin at a Carboxylated Multiwall Carbon Nanotube Modified Electrode and Its Analytical Applications

A novel type of carboxylated multiwalled carbon nanotube modified electrode（c-MWCNTs/GCE） was constructed and the electrochemical properties of phenacetin（PHE） at it were studied. In a buffer solution of 0.1 mol/L HAc-NaAc（pH=5.3）, PHE exhibited a couple of quasi-reversible redox peaks and an anodic peak in the poten- tial range of 0.2--1.2 V at c-MWCNTs/GCE. The peak current was proportional to the concentration of PHE in the range of 4.0× 10^-6_ 1.0 × 10^-4 mol/L with a detection limit of 1.0× 10^-6 mol/L（S/N=3）. The c-MWCNTs/GCE showed excellent repeatability and stability and the electrochemical reaction mechanism of PHE was proposed. This method was used to determine the content of PHE in medical tablets and the recovery was determined to be 96.5%--104.2% by means of a standard addition method.

Trace determination of zirconium using anodic adsorptive voltammetry at a carbon paste electrode modified with multi-walled carbon nanotubes

A carbon paste electrode modified with multi-walled carbon nanotubes (MWCNT) was prepared and the determination of ultra trace amount of zirconium based on the anodic adsorptive voltammetry of the zirconium-calcium-alizarin red S mix-polynuclear complex is described in this paper for the first time. The results showed that the sensitivity and the selectivity of the method are excellent. The second de-rivative linear scan voltammograms of the complex were recorded by polarographic analyzer from 200 to 1200 mV (vs. SCE) and it was found that the complex can be adsorbed on the surface of the electrode, yielding a peak at about 840 mV, corresponding to the oxidation of ARS in the complex. The peak cur-rent increases linearly with Zr (IV) concentration in the range of 6.0×10-12―6.0×10-11 mol·L-1 (accumu-lation time 120 s), 6.0×10-11―2.0×10-9 mol·L-1 (accumulation time 90 s) and 2.0×10-9―1.0×10-7 mol·L-1 (accumulation time 60 s) and the detection limit (S/N = 3) is 2.0×10-12 mol·L-1 (accumulation time 180 s). The procedure has been successfully applied to the determination of zirconium in the ore samples.

多壁碳纳米管/PEDOT复合修饰电极的制备及对苯二酚的测定

采用循环伏安法和悬凃法,在玻碳电极表面进行聚(3,4)-乙撑二氧噻吩(PEDOT)和多壁碳纳米管修饰,制备多壁碳纳米管-聚(3,4)-乙撑二氧噻吩复合修饰电极。通过扫描电镜观察复合电极的表面形貌,通过电化学阻抗谱(EIS)和循环伏安(CV)对复合电极进行电化学表征,用差分脉冲法(DPV)研究对苯二酚浓度与峰电流之间的线性关系。实验结果表明,制备的复合修饰电极对对苯二酚有明显的电催化作用,氧化还原峰电流明显增大;在p H为7.0的磷酸缓冲液(PBS)里,对苯二酚的峰电流最大。在1×10^(-5)~5×10^(-4)mol/L对苯二酚的浓度范围内,复合修饰电极的氧化峰电流值与浓度呈线性关系,其线性方程为y=47.95+0.0979x,R2=0.961,检出限为1.9×10^(-6)mol/L。制备的复合修饰电极能够增强电化学信号,具有较好的稳定性。