An electrochemical biosensor based on Nafion-ionic liquid and a myoglobin-modified carbon paste electrode

An electrochemical biosensor was constructed based on the immobilization of myoglobin (Mb) in a composite film of Nafion and hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF₆) for a modified carbon paste electrode (CPE). Direct electrochemistry of Mb in the Nafion-BMIMPF₆/CPE was achieved, confirmed by the appearance of a pair of well-defined redox peaks. The results indicate that Nafion-BMIMPF₆ composite film provided a suitable microenvironment to realize direct electron transfer between Mb and the electrode. The cathodic and anodic peak potentials were located at −0.351 V and −0.263 V (vs. SCE), with the apparent formal potential (Ep) of −0.307 V, which was characteristic of Mb Fe(III)/Fe(II) redox couples. The electrochemical behavior of Mb in the composite film was a surface-controlled quasi-reversible electrode process with one electron transfer and one proton transportation when the scan rate was smaller than 200 mV/s. Mb-modified electrode showed excellent electrocatalytic activity towards the reduction of trichloroacetic acid (TCA) in a linear concentration range from 2.0 × 10⁻⁴ mol/L to 1.1 × 10⁻² mol/L and with a detection limit of 1.6 × 10⁻⁵ mol/L (3σ). The proposed method would be valuable for the construction of a third-generation biosensor with cheap reagents and a simple procedure.     

One-step hydrothermal fabrication of nanosheet-assembled NiO/ZnO microflower and its ethanol sensing property

In this work, we report a simple synthesis of hierarchical flower-like NiO/ZnO heterostructure consisting of numerous nanosheets via a facile one-step hydrothermal method. The gas-sensing results reveal that the NiO/ZnO composite based sensor presents excellent properties towards ethanol such as high gas response and good repeatability. The excellent performances are predominantly ascribed to the p-n heterojunction strengthening at the interface between p-type NiO and n-type ZnO, which causes the change of depletion layer and potential barrier height. Moreover, the unique hierarchical architectures may play an evenly important role in the surface sensing reaction.     

碳糊电极和化学修饰碳糊电极制备及应用综述

综述了碳糊电极及化学修饰碳糊电极的发展、制备及表征,概括了近年来化学修饰碳糊电极在食品分析、药物分析、环境监测等领域的应用,并展望了其发展前景。     

Electrochemical oxidation and determination of antiretroviral drug nevirapine based on uracil-modified carbon paste electrode

A novel uracil covalently grafted carbon paste electrode (Ura/CPE) based on electro-deposition of uracil on CPE was prepared for the quantitative determination of nevirapine. The records of electrochemical impedance spectroscopy (EIS) and cyclic voltammograms (CV) in K₃Fe(CN)₆/K₄Fe(CN)₆ solution illustrated that uracil grafted on CPE efficiently decreased the charge transfer resistance value of electrode and improved the electron transfer kinetic between analyte and electrode. The electrochemical properties of Ura/CPE towards the oxidation of nevirapine were investigated by cyclic voltammetry and differential pulse voltammetry (DPV) in 0.1 M NaOH. The effects of pH and scan rates on the oxidation of nevirapine were studied. The results indicated the participation of the same protons and electrons in the oxidation of nevirapine, and the electrochemical reaction of nevirapine on Ura/CPE is an adsorption-controlled process. Under optimized conditions, the linearity between the oxidation peak current and nevirapine concentration was obtained in the range of 0.1–70.0 μM with detection limit of 0.05 μM and the sensitivity of 2.073 μA mM^?1 cm^?2 (S/N = 3). The proposed method was also successfully applied to detect the concentration of nevirapine in human serum samples.     

碳糊电极和化学修饰碳糊电极制备及应用研究进展

碳糊电极(CPE)是一种广泛应用于电化学领域的新型电极。将石墨粉和粘合剂混合成均匀的碳糊,然后将其挤压进电极管中便制成了碳糊电极。具有制备方法简单、背景电流小、无毒、电位窗口宽等优点,但由于制备过程中加入了不导电的粘合剂而降低了检测灵敏度。因此,制备碳糊电极时常加入修饰材料以提高电极的电化学性能。概述了碳糊电极和化学修饰碳糊电极的发展、制备方法和应用,对制备电极的材料和修饰剂的选用进行了分析。概括了近些年来化学修饰碳糊电极在不同领域的应用。     

碳糊电极和化学修饰碳糊电极制备及应用研究进展

碳糊电极(CPE)是一种广泛应用于电化学领域的新型电极.将石墨粉和粘合剂混合成均匀的碳糊,然后将其挤压进电极管中便制成了碳糊电极.具有制备方法简单、背景电流小、无毒、电位窗口宽等优点,但由于制备过程中加入了不导电的粘合剂而降低了检测灵敏度.因此,制备碳糊电极时常加入修饰材料以提高电极的电化学性能.概述了碳糊电极和化学修...     

Comparative investigation on electrochemical behavior of hydroquinone at carbon ionic liquid electrode, ionic liquid modified carbon paste electrode and carbon paste electrode

Ionic liquid, 1-heptyl-3-methylimidazolium hexafluorophosphate (HMIMPF₆), has been used to fabricate two new electrodes, carbon ionic liquid electrode (CILE) and ionic liquid modified carbon paste electrode (IL/CPE), using graphite powder mixed with HMIMPF₆ or the mixture of HMIMPF₆/paraffin liquid as the binder, respectively. The electrochemical behaviors of hydroquinone at the CILE, the IL/CPE and the CPE were investigated in phosphate buffer solution. At all these electrodes, hydroquinone showed a pair of redox peaks. The order of the current response and the standard rate constant of hydroquinone at these electrodes were as follows: CILE > IL/CPE > CPE, while the peak-to-peak potential separation was in an opposite sequence: CILE < IL/CPE < CPE. The results show the superiority of CILE to IL/CPE and CPE, and IL/CPE to CPE in terms of promoting electron transfer, improving reversibility and enhancing sensitivity. The CILE was chosen as working electrode to determine hydroquinone by differential pulse voltammetry, which can be used for sensitive, simple and rapid determination of hydroquinone in medicated skin cosmetic cream.     

Electrochemical fabrication of self assembled monolayer using ferrocene-functionalized gold nanoparticles on glassy carbon electrode

Electrochemical (EC) quantification of 11-Mercaptoundecylferrocene (thiolated-ferrocene substrate, Fc-SH) onto gold nanoparticles (AuNPs) was carried out through cyclic voltammetric (CV) investigations in different base electrolyte aqueous media on glassy carbon (GC) electrode. The electrochemical data including peak current, peak potential values revealed the Fc-SH–AuNPs redox system to be adsorption controlled in terms of self assembled monolayers (SAMs). The electrochemically generated SAMs were found quite stable as these maintained the redox activity upto 3 months after repeated CV scans at 298 K. The overall output of this research can be utilized in two ways: application of electroactivity and stability of these SAMs in detection of biologically important molecules and also towards the development of EC biosensors.     

Electrochemical determination of carbendazim in grapes and their derivatives by an ionic liquid-modified carbon paste electrode

Journal of Applied Electrochemistry - A novel electrochemical sensor containing an ionic liquid carbon paste electrode was synthesized to determine carbendazim in grape samples. The 2-hydroxy...     

Electrochemical characterization of tenoxicam using a bare carbon paste electrode under stagnant and forced convection conditions

From potentiostatic current transients and voltammetry studies, carried out under both stagnant and forced convection conditions, the tenoxicam electrochemical behavior on a bare carbon paste rotating disk electrode was assessed in an aqueous solution (pH = 0.403). It was found that tenoxicam's electrochemical oxidation is a mass transfer-controlled process where a current peak is clearly formed at around 0.74 V when the potential scan was varied in the positive direction. However, when the potential was switched to the negative direction, up to the initial potential value, no reduction peak was formed. Tenoxicam's electrochemical oxidation follows an EC mechanism where the electrodic and chemical kinetics are fast. From sample-current voltammetry both the number of electrons, n, that tenoxicam losses during its electro-oxidation and its half-wave potential, E_1/2, were determined to be 2 and 0.770 V vs. Ag/AgCl, respectively. Moreover, from differential pulse voltammetry plots it was confirmed that effectively in this case n = 2. Considering 2 electrons and both the Randles-Sevcik and Cotrell equations, the tenoxicam's diffusion coefficient, D, was determined to be (3.745 ± 0.077) × 10^?6 and (4.116 ± 0.086) × 10^?6 cm² s^?1, respectively. From linear sweep voltammetry plots recorded under forced convection conditions, it was found that Levich's equation describes adequately the limiting current recorded as a function of the electrode rotation rate, from where the D value was also found to be (4.396 ± 0.058) × 10^?6 cm² s^?1. Therefore, the average D value was (4.09 ± 0.33) × 10^?6 cm² s^?1. Furthermore, from the radius of the tenoxicam molecule, previously optimized at M052X/6-31 + G(d,p) level of theory, and using the Stokes–Einstein approach, D was also estimated to be 4.54 × 10^?6 cm² s^?1 which is similar to the experimentally estimated values, under both stagnant and forced convection hydrodynamic conditions.     

化学修饰碳糊电极的研究新进展

碳糊电极和化学修饰碳糊电极在电化学研究中起着非常重要的作用,综述了近年来化学修饰碳糊电极的优势及劣势、制备及应用,且分析了修饰剂的选择,最终对其进行了展望。     

Electrochemical characterization of screen-printed and conventional carbon paste electrodes

This work compares the electroactivity of a conventional carbon paste electrode and non-pretreated commercially available screen-printed carbon electrodes (from Alderon Biosciences, University of Florence and DropSens) towards some benchmark redox couples like hexaammineruthenium (III), ferricyanide, p-aminophenol and hydroquinone. While cyclic voltammograms of Ru³⁺ did not show significative electron transfer reactivity differences between the electrodes tested, the other redox systems exhibited higher reversible behaviours on DropSens electrodes. Scanning electron microscopy and roughness analysis with a profilometer were applied to detect the surface morphology of the working electrodes. The roughness evaluated of the screen-printed carbon working electrodes increased in this order Alderon < University of Florence < DropSens. Finally, the most electrochemically active and rough unpretreated electrode (DropSens commercial screen-printed electrode) was used to study the electrochemical-chemical reaction mechanism of indigo carmine oxidation in 0.1 M sulphuric acid. This study showed that the adsorption of the oxidation product of indigo carmine is stabilized when it is adsorbed on the surface of the electrode.     

Electrocatalytic reduction of dioxygen on hemin based carbon paste electrode

A hemin-modified carbon paste electrode was constructed by a simple, rapid and effective method. The electrochemical behaviour of the modified electrode was characterized by cyclic voltammetry. The modified electrode obtained was very stable and exhibited electrocatalytic response for the reduction of oxygen. The possible mechanism for the catalytic reduction of dioxygen is discussed. The dioxygen is reduced via a one-step reduction accompanying four electrons and four protons transfer at pH 7–11.     

Electrochemical characterization of cetyltrimethyl ammonium bromide modified carbon paste electrode and the application in the immobilization of DNA

A cetyltrimethyl ammonium bromide modified carbon paste electrode (CTAB/CPE) was developed in this work based on the surface modification method. The improved electrochemical response of K₄Fe(CN)₆ at this electrode indicated that CTAB could change the surface property of carbon paste electrodes (CPEs), which was demonstrated by the electrochemical impedance spectroscopy (EIS). In 0.1 mM [Fe(CN)₆]^3−/4−, a low exchange current (i₀) of 2.72×10⁻⁷ A at bare CPE was observed while that at CTAB/CPE was 6.79×10⁻⁵ A. The effect of CTAB concentration on the electrode quality revealed that CTAB formed a compact monolayer on the electrode surface with high density of positive charges directed outside the electrode. This electrode showed strong accumulation ability toward Fe(CN)₆⁴⁻ and can also accumulate Co(phen)₃²⁺ by the adsorption of the organic ligands in the hydrophobic area of the monolayer. The electrode was applied to the immobilization of DNA, which was characterized by the isotherm adsorption of Co(phen)₃²⁺.     

Electrocatalytic oxidation and simultaneous determination of uric acid and ascorbic acid on the gold nanoparticles-modified glassy carbon electrode

A new gold nanoparticles-modified electrode (GNP/LC/GCE) was fabricated by self-assembling gold nanoparticles to the surface of the l-cysteine-modified glassy carbon electrode. The modified electrode showed an excellent character for electrocatalytic oxidization of uric acid (UA) and ascorbic acid (AA) with a 0.306 V separation of both peaks, while the bare GC electrode only gave an overlapped and broad oxidation peak. The anodic currents of UA and AA on the modified electrode were 6- and 2.5-fold to that of the bare GCE, respectively. Using differential pulse voltammetry (DPV), a highly selective and simultaneous determination of UA and AA has been explored at the modified electrode. DPV peak currents of UA and AA increased linearly with their concentration at the range of 6.0 × 10⁻⁷ to 8.5 × 10⁻⁴ mol L⁻¹ and 8.0 × 10⁻⁶ to 5.5 × 10⁻³ mol L⁻¹, respectively. The proposed method was applied for the detection of UA and AA in human urine with satisfactory result.     

Electrochemical behavior and simultaneous determination of dihydroxybenzene isomers at a functionalized SBA-15 mesoporous silica modified carbon paste electrode

The simultaneous voltammetric determination of dihydroxybenzene isomers was investigated using cyclic and differential pulse voltammetries at the amino-functionalized SBA-15 mesoporous silica-modified carbon paste electrode (NH₂-SBA15/CPE) in phosphate buffer solution (pH 6.0). The NH₂-SBA15/CPE showed a larger peak current and higher selectivity for the dihydroxybenzene isomers in comparison with the bare carbon paste electrode (CPE) and SBA-15 mesoporous silica-modified carbon paste electrode (SBA15/CPE). The oxidation peak potential difference between hydroquinone (HQ) and catechol (CC) was 115 mV and was 396 mV between catechol and resorcinol (RC). This indicated that catechol, resorcinol and hydroquinone could be identified entirely at the NH₂-SBA15/CPE. Under the optimized conditions, the amperometric currents were linear over ranges from the following: 0.8–160 μmol L⁻¹ for hydroquinone, 1.0–140 μmol L⁻¹ for catechol and 2.0–160 μmol L⁻¹ for resorcinol. The detection limits were 0.3, 0.5 and 0.8 μmol L⁻¹, respectively. The proposed electrode can be applied to the simultaneous determination of dihydroxybenzene isomers in mixtures without previous chemical or physical separations.     

Electrochemical study of NiO nanoparticles electrode for application in rechargeable lithium-ion batteries

Nickel oxide nanoparticles were synthesized via a simple and inexpensive microwave-assisted synthesis method within a fast reaction time of less than 20 min. The calcination of as-prepared precursor at 600 °C produces single phase nickel oxide. The lattice structure and morphology of the sample were investigated by X-ray diffraction, field-emission scanning electron microscopy and field-emission transmission electron microscopy. The particle size range of the nickel oxide nanoparticles varied from 50 to 60 nm. Nickel oxide nanoparticles exhibited good electrochemical performances as an anode material for lithium-ion batteries. The prepared nickel oxide anode revealed a large initial discharge capacity of 1111.08 mAh g⁻¹ at 0.03 C rate and retained 80% of initial capacity (884.30 mAh g⁻¹) after 20 cycles. Furthermore, at elevated rate of 3.7 C, the charge capacity of the nickel oxide electrode was as high as 253.1 mAh g⁻¹, which was 35% greater than that of commercial bulk nickel oxide (188 mAh g⁻¹). The enhancement of the electrochemical performance was attributed to the high specific surface area, good electric contact among the particles and easier lithium ion diffusion.     

羧基化短碳纳米管修饰碳糊电极方波溶出伏安法测定尿酸

研究了尿酸在羧基化短碳纳米管修饰碳糊电极上的伏安行为.结果表明:在0.20 mol/L 磷酸盐(pH 5.79)介质中,此修饰电极对尿酸具有较好的电催化活性,该氧化峰的二阶导数峰电流与球酸浓度在7.0×10-7～1.0×10-5 mol/L范围内呈线性关系,相关系数为0.9988,检出限(S/N=3)为3.0×10-7...     

基于多壁碳纳米管修饰电极的磺胺的电化学检测

运用线性扫描伏安法(LSV)研究了磺胺(SA)在多壁碳纳米管修饰电极(MWNTs/GCE)上的电化学行为,探讨并确定了修饰体积和浓度、支持基质种类、最佳pH值、富集电位和时间等磺胺的最佳检测条件。结果表明,在pH=8.0的Na2HPO4-NaH2PO4缓冲体系中,磺胺在多壁碳纳米管修饰电极上检测到一个不可逆的氧化峰,且在1.0×10-5~2.0×10-4mol/L浓度范围内,磺胺氧化峰电流与其浓度呈现良好的线性关系,线性回归方程为Ip(μA)=0.493 6×C(μmol/L)+9.984 1,相关系数为R=0.996 3,检测下限为8.0×10-6mol/L,平行测定的相对误差(RSD)小于1.463%(n=8),样品平均加标回收率为99.21%~100.93%。     

基于多壁碳纳米管修饰电极的磺胺的电化学检测

运用线性扫描伏安法(LSV)研究了磺胺(SA)在多壁碳纳米管修饰电极(MWNTs/GCE)上的电化学行为,探讨并确定了修饰体积和浓度、支持基质种类、最佳pH值、富集电位和时间等磺胺的最佳检测条件。结果表明,在pH=8.0的Na2HPO4-NaH2PO4缓冲体系中,磺胺在多壁碳纳米管修饰电极上检测到一个不可逆的氧化峰,且在1.0×10-5².0×10-4mol/L浓度范围内,磺胺氧化峰电流与其浓度呈现良好的线性关系,线性回归方程为Ip(μA)=0.493 6×C(μmol/L)+9.984 1,相关系数为R=0.996 3,检测下限为8.0×10-6mol/L,平行测定的相对误差(RSD)小于1.463%(n=8),样品平均加标回收率为99.21%2.0×10-4mol/L浓度范围内,磺胺氧化峰电流与其浓度呈现良好的线性关系,线性回归方程为Ip(μA)=0.493 6×C(μmol/L)+9.984 1,相关系数为R=0.996 3,检测下限为8.0×10-6mol/L,平行测定的相对误差(RSD)小于1.463%(n=8),样品平均加标回收率为99.21%¹00.93%。