Carbon Film Electrodes Research Articles

Voltammetric Sensing of Amino Acids in the Presence of Cu(II) in Acidic and Alkaline Solutions

AbstractA number of amino acids have been determined at carbon film electrodes in the presence of copper. Strongly acidic, 0.1 M HCl, in the presence of 0.1 mM Cu(II), as well as alkaline, 0.1 M NaOH, solution permit successful measurement of individual amino acids, clearer separation between oxidation of Cu and Cu‐complexes occurring in alkaline solution. Electrochemical impedance showed that Cu(II) facilitates charge transfer, particularly in alkaline medium. Square wave voltammetry with preconcentration increased the response compared to linear sweep voltammetry. Protein hydrolysis rates were monitored through determination of amino acids produced by decomposition, injecting samples into alkaline electrolyte solution.

Investigation of copper and silver nanoparticles deposited on a nitrogen-doped diamond-like carbon (N-DLC) film electrode for bio-sensing

An electrochemical method has been employed in this work to deposit copper and silver nanoparticles onto chemical-vapor-deposited nitrogen doped hydrogen amorphous diamond-like carbon (N-DLC) film electrodes. The electrochemical behaviors of the metal-nanoparticle-modified N-DLC electrodes have been characterized in the presence of glucose and hydrogen peroxide in the electrolyte. The copper and the silver nanoparticles possess high catalytic function for the oxidation of glucose and the reduction of hydro peroxide, respectively. The well-defined reduction responses of the reduction or hydrogen peroxide give the silver-nanoparticle-modified N-DLC electrodes high potential for application in hydrogen-peroxide sensing without a label.

Application of nanocrystalline graphite-like pyrolytic carbon film electrode for voltammetric sensing of lead

A nanocrystalline pyrolytic carbon film was employed as working electrode to detect micromolar-level concentrations of lead by anodic stripping voltammetery as an example of its potential applications in environmental analysis. The response was compared with conventional carbon-based electrodes such as glassy carbon, edge-plane pyrolytic graphite, and basal-plane pyrolytic graphite electrodes. The favorable properties of this carbon coating for Pb detection lie in its high degree of sensitivity, high response stability, low memory effect, and a good repeatability. The applicability of this sensor was tested on spiked tap water and river water samples.

Simultaneous electrochemical sensing of ascorbic acid, dopamine and uric acid at anodized nanocrystalline graphite-like pyrolytic carbon film electrode

Nanocrystalline graphite-like pyrolytic carbon film (PCF) electrode fabricated by a non-catalytic chemical vapor deposition (CVD) process was used for the simultaneous electrochemical sensing of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The electrode was studied with respect to changes in electrocatalytic activity caused by a simple and fast electrochemical pretreatment. The anodized electrode exhibited excellent performance compared to many chemically modified electrodes in terms of detection limit, linear dynamic range, and sensitivity. Differential pulse voltammetry (DPV) was used for the simultaneous determination of ternary mixtures of DA, AA, and UA. Under optimum conditions, the detection limits were 2.9μM for AA, 0.04μM for DA, and 0.03μM for UA with sensitivities of 0.078, 5.345, and 6.192AM−1, respectively. The peak separation was 219mV between AA and DA and 150mV between DA and UA. No electrode fouling was observed and good reproducibility was obtained in all the experiments. The sensor was successfully applied for the assay of DA in an injectable drug and UA in human urine by using standard addition method.

Carbon Film Electrodes as Support of Metallic Particles

Carbon Film Electrodes as Support of Metallic Particles

An sp2 and sp3 Hybrid Nanocrystalline Carbon Film Electrode for Anodic Stripping Voltammetry and Its Application for Electrochemical Immunoassay

A hybridized nanocrystalline carbon film electrode consisting of sp(2) and sp(3) bonds was investigated to reveal the reduction properties of Cd(2+) and for application as a highly sensitive and reliable electrochemical immunoassay. Conductive nanocrystalline carbon film consisting of about 60% sp(2) and 40% sp(3) bonds was fabricated using electron cyclotron resonance (ECR) sputtering equipment, and then the Cd(2+) concentrations were measured with an ECR sputtered carbon (ECR nano-carbon) electrode by employing an anodic stripping voltammetry (ASV) technique. The preconcentrated Cd was analyzed with Kelvin probe force microscopy and energy dispersive X-ray spectroscopy while observing the morphology change with an atomic force microscope and a scanning electron microscope. The preconcentrated Cd on the ECR nano-carbon electrode was revealed to be a thin sheet structure, which was significantly different from the Cd on a conventional carbon material that grows with a coralloid structure. The background current during an ASV measurement maintains a low level equivalent to that found with boron-doped diamond because the surface of the ECR nano-carbon is robust and angstrom-level flat. The carbon-electrode performance for ASV was improved by controlling its structure at a nanometer scale without any metal doping or coating. Finally, the ECR nano-carbon was used for biomolecular determination by electrochemical immunoassay with a CdSe nanoparticle label. Electrochemical immunoassay results were successfully obtained with the ECR nano-carbon, and they correlated well with fluorescence results obtained for CdSe nanoparticles.

Application of nanocrystalline graphite-like pyrolytic carbon film electrode for determination of thiols

The quantification of some biologically important amino acids, namely cysteine, homocysteine, and N-acetylcysteine, was reported using pyrolytic carbon film (PCF) electrodes. Optimum responses were observed for the carbon films fabricated at a deposition temperature of 1100 °C (PCF1100) by chemical vapor deposition (CVD). Electro-oxidation of these sulfur-containing compounds at the PCF1100 showed well-defined signals and no electrode fouling was observed during a set of experiments. The PCF1100 electrode exhibited good resistance against interference by ascorbic acid with distinct separation from cysteine in voltammetric signals. The performance of this electrode was comparable to and in some cases even better than those observed at other unmodified carbon-based electrodes and many chemically modified electrodes in terms of detection limit, linear dynamic range, and sensitivity. Moreover, the electrode was successfully applied for the determination of cysteine in a tissue growth medium and the results proved that the sensitivity is not affected by presence of a large variety of potential interferences in this medium.

Nanocrystalline graphite-like pyrolytic carbon film electrode for electrochemical sensing of hydrazine

Pyrolytic carbon film (PCF) electrode fabricated by a non-catalytic chemical vapor deposition (CVD) process was used as an electrochemical sensor for the detection of hydrazine. The electrode response was found to be electrocatalytic producing a reduction in the overpotential compared to other unmodified carbon-based electrodes such as glassy carbon (GC), basal-plane pyrolytic graphite (BPPG), and edge-plane pyrolytic graphite (EPPG) electrodes. The overall number of electrons involved in the electro-oxidation of hydrazine, the number of electrons involved in the rate-determining step, and diffusion coefficient of hydrazine at PCF electrode were estimated using cyclic voltammetry and chronoamperometry. The performance of PCF electrode was comparable to and in some cases even better than many chemically modified electrodes in terms of detection limit, linear dynamic range, and sensitivity. Moreover, the sensor exhibited fast response time (within 2 s), high response stability, and reproducibility. All the results indicated this sensor is suitable for hydrazine analysis.

Direct Electrooxidation of Ascorbic Acid at the Nanocrystaline Graphite‐like Pyrolytic Carbon Film Electrode

AbstractPyrolytic carbon films (PCFs) were prepared by chemical vapor deposition (CVD) at different deposition temperatures. As an example of using PCF electrode in electroanalysis, the direct electrooxidation of ascorbic acid (AA) at the PCF electrode was investigated and compared with common carbon‐based electrodes such as glassy carbon (GC), edge plane pyrolytic graphite (EPPG), and basal plane pyrolytic graphite (BPPG) electrodes. It was found that the PCF electrodes prepared under deposition temperatures higher than 1050 °C showed a higher sensitivity and lower overpotential compared to the other carbon electrodes. The electrode was successfully applied for determination of AA in real samples.

Application of Square Wave Anodic Stripping Voltammetry for Determination of Traces of Ti(I) at Carbon Electrodes In Situ Modified with Bi Films

AbstractBismuth films deposited in situ at glassy carbon and carbon film electrodes were tested for the determination of traces of Tl(I) separately and together with Zn(II) and Pb (II), in acetate buffer solution pH 3.7, using square wave anodic stripping voltammetry. Electrochemical impedance spectra in the presence of Tl(I) showed differences between the electrode substrates. The sensitivity to Tl does not depend on the presence of other ions, and was better at carbon film electrodes, although the 2 nmol L−1 detection limit was independent of electrode substrate. Application to the measurement of Tl(I) in commercial berry juice is demonstrated.

Efficient Direct Electron Transfer with Enzyme on a Nanostructured Carbon Film Fabricated with a Maskless Top-Down UV/Ozone Process

We have developed a new carbon film electrode material with thornlike surface nanostructures to realize efficient direct electron transfer (DET) with enzymes, which is very important for various enzyme biosensors and for anodes or cathodes used in biofuel cells. The nanostructures were fabricated using UV/ozone treatment without a mask, and the obtained nanostructures were typically 2-3.5 nm high as confirmed by atomic force microscopy measurements. X-ray photoelectron spectroscopy and transmission electron microscopy revealed that these nanostructures could be formed by employing significantly different etching rates depending on nanometer-order differences in the local sp(3) content of the nanocarbon film, which we fabricated with the electron cyclotron resonance sputtering method. These structures could not be realized using other carbon films such as boron-doped diamond, glassy carbon, pyrolyzed polymers based on spin-coated polyimide or vacuum-deposited phthalocyanine films, or diamond-like carbon films because those carbon films have relatively homogeneous structures or micrometer-order crystalline structures. With physically adsorbed bilirubin oxidase on the nanostructured carbon surface, the DET catalytic current amplification was 30 times greater than that obtained with the original carbon film with a flat surface. This efficient DET of an enzyme could not be achieved by changing the hydrophilicity of the flat carbon surface, suggesting that DET was accelerated by the formation of nanostructures with a hydrophilic surface. Efficient DET was also observed using cytochrome c.

Oxidation Behavior of Glucose on Platinized Diamond-like Carbon Film Electrode

In order to improve the electrochemical activity of conductive diamond-like carbon(DLC) film,platinized DLC(DLC-Pt) film was prepared by magnetron co-sputtering of graphite and platinum targets.The compositions and microstructures of DLC-Pt film were investigated by X-ray photoelectron spectroscope and Raman spectroscope,and the oxidation behaviors of glucose at the DLC-Pt film surface were examined by cyclic voltammetry.The results indicate that DLC-Pt film has more sp~2 carbon atoms compared with DLC film,and the redox reaction of K_3Fe(CN)_6 on the DLC-Pt film electrode is controlled by diffusion.The glucose oxidation starts at about -0.8 V on the DLC-Pt film surface without interference from urea and ascorbic acid.A linear detection range of glucose obtained on the DLC-Pt electrode is identified from 2 mmol/L to 22 mmol/L(covering blood glucose levels in diabetic patients).So the DLC-Pt film has potential application to be a glucose sensor for blood glucose defection.

Preparation and characterisation of poly(3,4-ethylenedioxythiophene) and poly(3,4-ethylenedioxythiophene)/poly(neutral red) modified carbon film electrodes, and application as sensors for hydrogen peroxide

Poly(3,4-ethylenedioxythiophene) (PEDOT) films have been prepared for the first time on carbon-film electrodes (CFE) in aqueous solution using electropolymerisation by potential cycling, potentiostatically and galavanostatically. Characterisation of the modified electrodes was done by cyclic voltammetry and electrochemical impedance spectroscopy and the stability of the polymer films was probed. The coated electrodes were tested for application as hydrogen peroxide sensors, by oxidation and reduction. A novel polymer film was also formed by modification of CFE by co-electropolymerisation of EDOT and the phenazine dye neutral red (NR) – (PEDOT/PNR) with a view to enhancing the properties for sensor applications. It was found that hydrogen peroxide reduction at the PEDOT/PNR coated electrodes could be carried out at a less negative potential, the sensor performance comparing very favourably with that of other polymer-modified electrodes reported in the literature.

Three dimensional film electrode prepared from oppositely charged carbon nanoparticles as efficient enzyme host

Three dimensional carbon film electrodes were prepared from oppositely charged carbon nanoparticles (ca. 9 to 18 nm diameter) by a layer-by-layer approach. This was done by alternative immersion of indium tin oxide plates into suspension of positively and negatively charged particles. A stable film is formed already after single immersion and withdrawal step as confirmed by scanning electron microscopy. Up to ten immersion and withdrawal steps can be used to systematically increase the amount of nanoparticulate carbon material. The capacitive current density and current density of hydrogen peroxide reduction are proportional to the number of immersion and withdrawal steps. The same can be seen for adsorbed redox active 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate). After adsorption of bilirubin oxidase into the film efficient bioelectrocatalytic dioxygen reduction is observed.

Dependence of catalytic activity and long-term stability of enzyme hydrogel films on curing time

Enzyme hydrogels were prepared on carbon film electrodes using glucose oxidase and an epoxide crosslinking agent. The catalytic activity of the gels was found to depend strongly on curing time. The competing effects of increased mechanical stability and decreased enzyme activity as curing time increases resulted in the highest catalytic activity for films cured for 24 h at 25 °C. Weekly electrochemical measurements established that the long-term stabilities of all hydrogels cured for 24–72 h were similar, with close to half of the initial catalytic activity being retained after immersion for 3 months in agitated phosphate buffer solution at 25 °C.

Microscopic and electrochemical characterization of lead film electrode applied in adsorptive stripping analysis

Lead film electrodes (PbFEs) deposited in situ on glassy carbon or carbon paste supports have recently found application in adsorptive stripping voltammetric determination of inorganic ions and organic substances. In this work, the PbFE, prepared in ammonia buffer solutions, was investigated using scanning electron microscopy, atomic force microscopy and various voltammetric techniques. The microscopic images of the lead films deposited on the glassy carbon substrate showed a considerable variability in microstructure and compactness of the deposited layer depending on the selected experimental conditions, such as the concentration of Pb(II) species, the nucleation and deposition potential, and the time applied. The catalytic adsorptive systems of cobalt and nickel in a solution containing 0.1 ammonia buffer, 2.5 × 10 −5 M nioxime and 0.25 M NaNO 2 were employed to investigate the electrochemical characteristics and utility of the in situ prepared lead films. The optimal parameters, i.e. the lead concentration in the solution, the procedure of film removal, and the time and potential of lead nucleation and film deposition for the adsorptive determination of metal traces, were selected, resulting in the very good reproducibility (RSD = 4.2% for 35 scans) of recorded signals. The voltammetric utility of the lead film electrode was compared to that of glassy carbon, mercury film and bismuth film electrodes, and was subsequently evaluated as superior.

A strategy for immobilisation of carbon nanotubes homogenised in room temperature ionic liquids on carbon electrodes

Functionalised multi-walled carbon nanotubes (MWCNT) were homogenised in the room temperature ionic liquids (RTILs) 1-butyl-3-methylimidazolium bis(trifluoromethane)sulfonimide (BmimNTF 2), 1-butyl-1-methylpyrrolidinium bis(trifluoromethane)sulfonimide (BmpyNTF 2) and 1-butyl-3-methylimidazolium nitrate, and the composite obtained was applied on the top of glassy carbon or carbon film electrode substrates. The modified electrodes were characterised electrochemically in aqueous electrolytes and ionic liquids using cyclic voltammetry and electrochemical impedance spectroscopy and the model redox couples potassium hexacyanoferrate and ferrocene were used for electrode characterisation in aqueous and RTIL media, respectively. It was found that the combination of MWCNT with BmimNTF 2 gave the best composite which augurs well for application in sensors and biosensors.

Physiologically Relevant Online Electrochemical Method for Continuous and Simultaneous Monitoring of Striatum Glucose and Lactate Following Global Cerebral Ischemia/Reperfusion

This study demonstrates a new electroanalytical method with a high physiological relevance for simultaneous online monitoring of glucose and lactate in the striatum of the rat brain following global cerebral ischemia/reperfusion. The online analytical method is based on the efficient integration of in vivo microdialysis sampling with an online selective electrochemical detection with the electrochemical biosensors with dehydrogenases, i.e., glucose and lactate dehydrogenases, as recognition elements. The dehydrogenase-based electrochemical biosensors are developed onto the dual split-disk plastic carbon film (SPCF) electrodes with methylene green (MG) adsorbed onto single-walled carbon nanotubes (SWNTs) as the electrocatalyst for the oxidation of dihydronicotiamide adenine dinucleotide (NADH) at a low potential of 0.0 V (vs Ag/AgCl). Artificial cerebrospinal fluid (aCSF) containing NAD(+) is externally perfused from a second pump and online mixed with the brain microdialysates to minimize the variation of pH that occurred following the cerebral ischemia/reperfusion and to supply NAD(+) cofactor and O(2) for the enzymatic reactions of dehydrogenases and ascorbate oxidase, respectively. As a result, the developed online electroanalytical method exhibits a high selectivity against the electrochemically active species endogenously existing in the cerebral systems and a high tolerance against the variation of pH and O(2) following cerebral ischemia/reperfusion. This property, along with the good linearity and a high stability toward glucose and lactate as well as little cross-talk between two biosensors, substantially makes this method possible for the continuous, simultaneous, and online monitoring of glucose and lactate in the rat brain following global cerebral ischemia/reperfusion. This study establishes a new and effective platform for the investigation of the energy metabolism in physiological and pathological processes.

Electrosynthesis and characterisation of poly(safranine T) electroactive polymer films

The phenazine safranine T has been electropolymerised by potential cycling at carbon film electrodes in nitrate-containing solutions at different pH: 2.0, 5.5, and 7.0, as well as from chloride solution, pH 5.5. The electroactive polymer obtained, poly(safranine T), has been analysed by cyclic voltammetry in different electrolyte solutions and its morphology examined using scanning electron microscopy. The surface coverage was calculated and found to be the highest for the film formed in chloride solution, pH 5.5, with 8.7 nmol cm − 2 . The other films had lower coverages, from 5.3 to 7.8 nmol cm − 2 , and are similar to those obtained for other phenazine dye polymers. Although the fastest polymerisation occurred in solutions at pH 5.5, the best electrochemical properties resulted from electropolymerisation at pH 2.0. Analysis of the cyclic voltammograms showed that in most cases the electrochemical processes at the polymer coated electrodes are limited by surface reactions. Scanning electron microscopy data confirmed the results obtained by cyclic voltammetry and showed that the most compact film was obtained in chloride solution.

Electrochemical Properties of Ordered Mesoporous Carbon Film Adsorbed onto a Self‐Assembled Alkanethiol Monolayer on Gold Electrode

AbstractA stable ordered mesoporous carbon (OMC) film electrode was successfully constructed by adsorbing OMC onto a self‐assembled monolayer (SAM) of C18H37SH chemisorbed on the Au electrode. Transmission electron microscopy (TEM), atomic force microscopy (AFM), and electrochemical methods were used to characterize the properties of the OMC film electrode. The adsorbed OMC can restore the heterogeneous electron transfer almost totally blocked by the alkanethiol monolayer. Nyquist plots show a sharply decrease of the charge transfer resistance (Rct) of the Fe(CN)$\rm{ {_{6}^{3-/4-}}}$ couple at the OMC film electrode. Furthermore, the OMC film electrode is found to possess a significantly reduced interfacial capacitance and largely enhanced current response of hydrogen peroxide. This novel approach to the fabrication of stable OMC film electrode with excellent electrochemical properties is believed to be very attractive for electrochemical studies and electroanalytical applications.