碳薄膜电极材料在电分析化学中的应用

由于具有一系列的优点,碳材料被广泛地应用于电分析化学。新型碳电极材料的开发及其性质研究对电分析化学的发展起着重要的推动作用。最近文献报道了一些制备新型碳薄膜电极材料的方法,因为制备方法不同,这些碳薄膜材料的电化学性质如电位窗、稳定性、导电性也显著不同。人们对电位窗宽、背景电流低、稳定性高、表面不易被电极产物钝化的碳薄膜电极材料的研究非常活跃。本文综述了采用不同方法制备的一些碳薄膜电极材料如硼掺杂的金刚石薄膜、无定形碳和纳米晶体碳薄膜材料等在电分析化学中应用。     

Electrochemical behavior of nanocrystalline diamond thin films grown in electrical arc plasma

Nitrogenated nanocrystalline diamond films with controlled electrical conductivity are grown in electrical arc plasma in CH₄/H₂/Ar/N₂ gas mixtures and characterized by scanning electron microscopy and spectroscopic measurements. Their electrochemical properties are studied by electrochemical impedance spectroscopy. Transfer coefficients of reactions in the [Fe(CN)₆]^3−/4− redox system are determined. The electrochemical behavior of the material is controlled by its nitrogenation (3–20% N₂ in the reaction gas mixture). The nitrogenated nanocrystalline diamond has higher differential capacitance in indifferent electrolyte (1 M KCl) solution than not nitrogenated one; the nitrogenation also increases the reversibility of reactions in the [Fe(CN)₆]^3−/4− redox system. By and large, with nitrogenation of diamond, its electrochemical behavior changes from the one characteristic of a “poor conductor” to that characteristic of metallike conductor. In this respect the nanocrystalline diamond electrodes grown in the electrical arc plasma are similar to those grown in microwave plasma.     

Diamond microelectrodes for in vitro electroanalytical measurements: current status and remaining challenges

An emerging research field in electrochemistry today is the preparation, characterization and application of diamond microelectrodes for electroanalytical measurements in biological media. Interest in this new electrode material stems from its outstanding properties: (i) hardness, (ii) low, stable and pH-independent background current, (iii) morphological and microstructural stability over a wide range of potentials, (iv) good electrochemical responsiveness for multiple redox analytes without any conventional pre-treatment and (v) weak molecular adsorption of polar molecules that leads to a high level of resistance to response deactivation and electrode fouling. Diamond electrodes have advanced in recent years from being simply a scientific curiosity into a viable material for electroanalysis. In this article, we highlight the current state of progress by our laboratory and others on the preparation, study of the basic electrochemical properties, and application of this new type of microelectrode for in vitro electroanalytical measurements, and discuss some of the remaining challenges.     

The Influence of Doping Levels and Surface Termination on the Electrochemistry of Polycrystalline Diamond

The influence of surface chemistry and boron doping density on the redox chemistry of Fe(CN) at CVD polycrystalline diamond electrodes is considered. It is demonstrated that for this couple both the doping density and the surface chemistry are important in determining the rate of charge transfer at the electrode/electrolyte interface. For hydrogen terminated CVD diamond metallic electrochemical behavior is always observed, even at boron doping densities as low as 7×10¹⁸ cm^?3. In contrast, the electrochemical behavior of oxygen terminated CVD diamond varies with doping density, a metallic response being observed at high doping density and semiconductor behavior at low doping density. It is shown that the results attained may be explained by a surface state mediated charge transfer mechanism, thus demonstrating the importance of controlling surface chemistry in electroanalytical applications of diamond.     

Chemically Modified Carbon Nanotubes for Use in Electroanalysis

The discovery of carbon nanotubes has had a profound impact on many areas of science and technology, not least that of electroanalysis. The properties and applications of carbon nanotubes themselves have been well reviewed in the literature and a number of reviews with an electrochemical emphasis have been published. However, the modification of carbon nanotubes has recently been the focus of much research, primarily to improve their solubility in various solvents. Yet modified carbon nanotube electrodes also allow the electrochemist to tailor the properties of the carbon nanotubes, or the electrode surface to impart desired properties such as enhanced sensing capabilities. In this review we attempt to comprehensively cover the different chemical and electrochemical modification strategies and research carried out using modified carbon nanotubes for electroanalytical and bioanalytical applications. Furthermore we also discuss the use of modified carbon nanotubes in electrocatalysis and biocatalysis from an analytical aspect, as well as seeking to dispel some of the myths surrounding the “electrocatalytic” properties of carbon nanotubes.     

A simple adsorptive chronopotentiometric stripping method for determination of vitamin B 1 in pharmaceutical products

A new electroanalytical method for vitamin B1 determination, based on adsorptive chronopotentiometric stripping analysis and non-specific adsorption onto mercury film electrode, was developed and validated. Stripping chronopotentiograms showed a single well-defined oxidation wave corresponding to vitamin B1 at about − 0.43 V in citrate buffer pH 6.0. The most important experimental factors affecting the monitored electroanalytical response of vitamin B1 were investigated and optimised. Under the optimal experimental conditions, linear response of vitamin B1 was obtained in the concentration range of 5–50 mg dm−3, with the achieved limit of detection of 1.64 mg dm−3, and the limit of quantitation of 4.97 mg dm−3. A mean recovery of 97.1% and relative standard deviations of 3.75% were achieved. The developed electrochemical procedure was successfully applied for the determination of vitamin B1 in pharmaceutical products. The results of the proposed method were in good agreement with those obtained by parallel HPLC analyses, confirming an accuracy of the developed method.     

The application of electroanalytical methods to the analysis of phase transitions during intercalation of ions into electrodes

Mechanisms of first-order phase transition induced by electrochemical intercalation of Li ions into composite graphite electrode are studied both theoretically, in the framework of lattice gas models, and experimentally, by a combination of electroanalytical techniques, such as cyclic voltammetry, potentiostatic intermittent titration (PITT), galvanostatic intermittent titration (GITT), and electrochemical impedance spectroscopy (EIS). From the analysis of the mismatch between the accessible phase-transition rate constants and the characteristic time windows for various electroanalytical methods, we conclude that only a combined application of these techniques provides sufficient, self-consistent information on the mechanisms of phase transitions in graphite electrodes. The advantages and disadvantages in using these techniques are discussed. PITT with a small potential step is the most appropriate tool for measuring the entire sequence of rate-determining steps of phase transitions as a function of time. The latter technique can be conveniently used for quantitative analysis of slow nucleation and the growth of new phases in the bulk of the old one, followed by the coalescence of nuclei and the formation of phase boundaries between the coexisting phases. The movement of this boundary into the electrode’s bulk has been properly modeled in terms of two alternative models. “Contribution to the International Workshop on Electrochemistry of Electroactive Materials (WEEM-2006), Repino, Russia, 24–29 June 2006.”     

Electrodes of synthetic diamond: The effects of Ti substrate pretreatment on the electrode properties

The electrode properties of boron-doped diamond thin films grown on Ti substrates by a hot-filament chemical vapor deposition technique are evaluated. The Ti substrate surface modifying conditions are devised, involving the surface roughening, annealing, and etching, which effectively improve the diamond electrode properties. The preetching of the Ti substrate produces the titanium hydride layer that can affect the boron-doped diamond film growth significantly. The substrate roughened surface obviously improved the diamond film adhesion and reduced the inner stress. The electrodes reveal minimal background current and better stability. A wider potential window, up to 3 V, is observed for the boron-doped diamond on the etched/annealed samples. The electrochemical activity of the electrodes in the Fe(CN) ₆ ^3-/4- redox system somewhat increases with increasing surface roughness. The apparent increase in the reversibility of the reaction may be explained by the decrease in the true current density. Suitability of the Ti-based boron-doped diamond electrodes for electroanalytical applications is exemplified by sensing the trace metal ions, such as Hg²⁺ and Pb²⁺.__________From Elektrokhimiya, Vol. 41, No. 4, 2005, pp. 387–396.Original English Text Copyright © 2005 by Pleskov, Evstefeeva, Krotova, Lim, Chu, Ralchenko, Vlasov, Kononenko, Varnin, Teremetskaya, Shi.This article was submitted by the authors in English.     

Recent electroanalytical applications of boron-doped diamond electrodes

This review overviews recent reports on the electroanalytical applications of boron-doped diamond (BDD) electrodes. Because BDD electrodes have excellent features for electroanalysis, such as wide potential window, low background current, electrochemical stability, and fouling resistance, they can be useful for sensitive and stable detection of various substances, including drugs, bio-related substances, metal ions, and organic pollutants. Many articles have reported high-sensitivity detection of real samples, demonstrating that this electrode material is practically applicable. Surface modification of the BDD electrodes using metal nanoparticles, nanocarbons, and polymers can increase the sensitivity of the electrochemical detection. Furthermore, research on the electroanalytical device equipped with BDD electrodes will be expanded by combining peripheral technologies related to the device fabrication.     

Fabrication and characterization of boron doped diamond microelectrode arrays of varied geometry

Boron doped diamond (BDD) is a well-known electrode material that exhibits an excellent electrochemical potential window with very low background current. With this, microelectrodes and microelectrode arrays (MEAs) have been found to even further lower background currents without compromising sensitivity. As such, BDD MEAs are excellent electrode materials for a variety of electroanalytical applications, capable of multi-mode detection. We fabricated BDD MEAs adapting traditional semiconductor microfabrication processes; the resulting MEAs were patterned in different geometries to find an optimum electrochemical response, depending on the application. This is demonstrated using 4 different MEA geometries of different size and spacing using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), where the charge transfer resistance (R_ct) increases as the electrodes are farther spaced from one another. Excellent sigmoidal voltammogram shape in CV was obtained for each BDD MEA geometry. BDD MEAs spaced farther from one another were found to give better resolution from the background in fast scan cyclic voltammetric measurements of dopamine due to the decrease in the double layer capacitance (C_dl) as verified with EIS. This work furthers the understanding of BDD MEAs and their pertinence to sensitive electroanalytical techniques.     

Electrochemical study of some non-steroidal anti-inflammatory drugs: solvent effect and antioxidant activity

The electrochemical behavior of 12 non-steroidal anti-inflammatory drugs (NSAIDs) was studied by means of cyclic voltammetry at a glassy carbon electrode. The underlying solvent had a considerable effect to the oxidation potentials of the investigated NSAIDs due to the alteration of their polar intermediates’ solvation. Oxicams were more capable of electrochemical oxidation, and the influence of both specific and non-specific solute–solvent interactions in their reactivity was confirmed by means of Kamlet–Taft’s analysis. Oxicams were further studied by chronoamperometry at the potentials of 300, 500, and 800 mV. The results obtained by the employed electroanalytical techniques were compared with the reactivity of oxicams towards 1,1- diphenyl-2-dipicrylhydrazyl (DPPH). The study showed a correlation of oxicams’ amperometric signal at 800 mV with their absolute reaction rate, z with DPPH.     

Electroanalytical Approach for Quantification of Pesticide Maneb

For the first time, in this study electrochemical oxidation behavior of pesticide maneb is evaluated. Due to the structure electroanalytical quantification of maneb has not been exploited enough. Maneb electrochemical behavior was investigated using glassy carbon (GC), graphene modified glassy carbon (GR/GC) and boron doped diamond (BDD) electrodes. It is shown that only BDD shows satisfactory results toward maneb detection. Based on this, a simple, sensitive and selective electroanalytical method for determination of pesticide maneb using differential pulse voltammetry (DPV) is proposed, with a working linear range of 80–3000 nM and the limit of detection of 24 nM. The developed methodology has been applied for the determination of maneb in river water samples with satisfactory recovery. Additionally, this green method, being simple, fast, and free of chemical‐reduction reagents, offers several advantages over modified electrodes and expands the scope of BDD based electrochemical sensing devices, with promise for wider applications in environmental analysis.     

Electropolymerizing polyaniline on undoped 100 nm diamond powder and its electrochemical characteristics

Conductive polyaniline (PANI) was electropolymerized on undoped 100 nm diamond powders in sulphuric acid solution containing aniline to improve the conductivity and the electrochemistry of the nano- or submicro-scaled diamond particles. Cyclic voltammetry (CV) experiment was carried out at an upper potential of 1.1 V in initial sweeps and a potential range of ?0.2–0.9 V for the growth of PANI on a diamond powder electrode. Field emission-scanning electron microscope (FESEM) result reveals that the diamond particles were well coated by PANI films with globular or fibroid surface morphology. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were employed to investigate the electrochemical properties of the PANI/diamond composite electrode. It presents lower resistance and better capacitance than the pristine diamond powder.     

A Fast and Simple Ozone‐mediated Method towards Highly Activated Screen Printed Carbon Electrodes as Versatile Electroanalytical Tools

A facile and effective electrochemical activation method of screen printed carbon electrodes (SPCEs) has been performed using ozone gas. Activated SPCEs showed relevant improvements in the electrochemical properties such as an impedance reduction and better electroanalytical outcomes. Such improved properties were attributed to the increase of the electroactive surface area and the functionalization of the electrode surface with carbon‐oxygen groups onto the carbonaceous ink surface. The optimized activation method consisted in the performance of a voltammetric cycle between ?2 and 2 V at 10 mV s^?1 in 0.1 M NaOH solution with constant ozone gas bubbling. This activation procedure takes 12 min, which allows its use routinely prior to the electrode modifications and electroanalytical measurements. The resulting activated SPCEs exhibited superior sensitivities towards hydrogen peroxide, acetaminophen, hydroquinone and dopamine. This methodology might be considered as a strategy to attain SPCEs with improved electroanalytical properties for multiple applications.     

Metal ion analysis in contaminated water samples using anodic stripping voltammetry and a nanocrystalline diamond thin-film electrode

Boron-doped nanocrystalline diamond thin-film electrodes were employed for the detection and quantification of Ag (I), Cu (II), Pb (II), Cd (II), and Zn (II) in several contaminated water samples using anodic stripping voltammetric (ASV). Diamond is an alternate electrode that possesses many of the same attributes as Hg and, therefore, appears to be a viable material for this electroanalytical measurement. The nanocrystalline form has been found to perform slightly better than the more conventional microcrystalline form of diamond in this application. Differential pulse voltammetry (DPASV) was used to detect these metal ions in lake water, well water, tap water, wastewater treatment sludge, and soil. The electrochemical results were compared with data from inductively coupled plasma mass spectrometric (ICP-MS) and or atomic absorption spectrometric (AAS) measurements of the same samples. Diamond is shown to function well in this electroanalytical application, providing a wide linear dynamic range, a low limit of quantitation, excellent response precision, and good response accuracy. For the analysis of Pb (II), bare diamond provided a response nearly identical to that obtained with a Hg-coated glassy carbon electrode.     

Determination of Sodium Diethyldithiocarbamate in Water by Anodic Voltammetry Using a Boron‐Doped Diamond Electrode

An electrochemical study was made of the anodic behavior of sodium diethyldithiocarbamate (DEDTC) using a boron‐doped diamond electrode (BDDE) in sodium sulfate supporting electrolyte. This paper presents a new alternative for the electroanalytical determination of DEDTC in protic media, using cyclic voltammetry or chronoamperometry. Linear plots of current vs. concentration correlated with anodic stepwise oxidation were obtained in delimited potential ranges with very good correlation coefficients.     

Electrochemistry of Methyl Viologen and Anthraquinonedisulfonate at Diamond and Diamond Powder Electrodes: The Influence of Surface Chemistry

The electrochemical behaviour of methyl viologen and anthraquinonedisulfonate was studied at electrodes produced from differing forms of diamond, including microcrystalline boron doped diamond, boron doped diamond powder and detonation nanodiamond powder. Two types of electrode pretreatment were employed to produce two dissimilar surface terminations: hydrophobic H‐terminated and hydrophilic O‐terminated. In the case of methyl viologen, it was found that the reduced neutral molecule adsorbed on all three electrodes if they were hydrogen terminated, but not if they were oxygen terminated. For anthraquinonedisulfonate, no adsorption was found on the solid diamond electrode, although again significant adsorption was noted on the powder electrodes, provided they were hydrogen terminated. The reasons underlying these observations are discussed in terms of hydrophobic and electrostatic interactions and the electrode morphology. The work provides information into the likely occurrence of adsorption and concomitant electrode fouling, which may be experienced in electroanalytical applications using solid and powdered forms of diamond.     

Square wave voltammetric determination of nitrofurantoin in pharmaceutical formulations on highly boron-doped diamond electrodes at different boron-doping contents

The influence of the boron-doping levels in boron-doped diamond film electrodes on the electrochemical response of nitrofurantoin (NFT) and the development of an electroanalytical procedure for NFT determination were investigated. The investigations were carried out using the techniques of cyclic voltammetry and square wave voltammetry on diamond film electrodes with different boron-doping levels (i.e., 5000, 10,000 and 20,000 mg L⁻¹). The level of boron-doping in the diamond film electrodes influenced the electrochemical reduction of NFT. The appropriate cyclic voltammetric response of NFT was obtained with Britton-Robinson buffer at pH 4 and for diamond films doped with 10,000 and 20,000 mg L⁻¹ of boron. These two films were selected for the development of the electroanalytical procedure. The use of square wave voltammetry with the optimized parameters demonstrated a good linear relationship between the peak current and the NFT concentration for a wide range of concentration. The lower limit of detection for the electrodes doped with 10,000 and 20,000 mg L⁻¹ of boron were 2.69 × 10⁻⁸ mol L⁻¹ (6.40 μg L⁻¹) and 8.15 × 10⁻⁹ mol L⁻¹ (1.94 μg L⁻¹), respectively, while the lower limits of quantification were 8.96 × 10⁻⁸ mol L⁻¹ (21.33 μg L⁻¹) and 2.72 × 10⁻⁸ mol L⁻¹ (6.47 μg L⁻¹), respectively. The applicability of the proposed procedure was tested using a commercial pharmaceutical formulation of NFT, and the results were compared with the procedure recommended by the British Pharmacopeia. The proposed procedure was sensitive, accurate and precise for analysis of NFT and did not require complex preparations or renovations of the electrode surface. This presents the advantage of eliminating mercury waste and minimizing the adsorptive problems related to the use of other electrodic solid surfaces.     

Laser-induced Graphene in Facts,Numbers, and Notes in View of Electroanalytical Applications: A Review

In this review, laser-induced graphene (LIG) -based electrodes are discussed by covering such essential areas, as a characterization of LIG material properties necessary for electroanalysis, including data on LIG sheet resistance, wettability, spatial resolution, electrochemical characteristics, as well as correlations of “process” - “properties” - “electroanalytical characteristics”of LIG-electrodes. Moreover, typical and innovative LIG-based electrodes designs for electroanalytical applications, including combined multi-analyte multimodal wearable sensors, interdigitated electrodes, are shown. The essential data related to LIG in electroanalysis are summarized in tables. The authors also discussed recent LIG-based electroanalytical applications. Close attention has been paid to LIG glucose sensors and biosensors.     

Hydroxyl radicals electrochemically generated in situ on a boron-doped diamond electrode

The hydroxyl radicals electrochemically generated in situ on a boron-doped diamond (BDD) electrode have been investigated for the first time in different electrolyte media, over the whole pH range between 1 and 11. A more extensive characterisation of BDD electrochemical properties is very important to understand the reactivity of organic compounds towards electrochemical oxidation on the BDD electrode, which is related to their interaction with adsorbed hydroxyl radicals due to water oxidation on the electrode surface. An oxidation peak corresponding to the transfer of one electron and one proton was observed in pH <9 electrolytes, associated with the water discharge process and electrochemical generation of hydroxyl radicals, which can interact and enhance the electro-oxidation of organic compounds. In pH >9 electrolytes the electrochemical generation of hydroxyl radicals was not observed; ammonia buffer electrolyte gave a pH-independent peak corresponding to the ammonia oxidation reaction. Additionally, for most pH values studied, a few small peaks associated with the electrochemical interaction between non-diamond carbon species on the doped diamond electrode surface and the electrolyte were also seen, which suggests that the doped diamond is relatively unreactive, but not completely inert, and the electrogenerated hydroxyl radicals play a role as mediator in the oxidation of organics.