Boron-doped Diamond Thin-film Electrodes Research Articles

Spatially Heterogeneous Electrical and Electrochemical Properties of Hydrogen-Terminated Boron-Doped Nanocrystalline Diamond Thin Film Deposited from an Argon-Rich CH4/H2/Ar/B2H6 Source Gas Mixture

Spatially heterogeneous electrical and electrochemical properties were observed for hydrogen-terminated, boron-doped nanocrystalline diamond thin-film electrodes by conducting-probe atomic force microscopy (CP-AFM) and scanning electrochemical microscopy (SECM). CP-AFM was used to simultaneously map the topography and electrical conductivity of the film as a function of the boron-doping level and bias voltage. The electrode was characterized by areas of high electrical conductivity separated by regions of low conductivity. The fraction of a particular film's area that exhibited high conductivity remained invariant with the polarity and magnitude of the bias voltage, while the current flow at any of the conductive regions increased proportionally with the bias voltage indicative of metal-like electronic properties. The fraction of highly conductive area increased with the doping level. One possible cause for the differential conductivity across a film is a nonuniform distribution of boron dopant, which leads to a nonuniform charge carrier concentration. SECM was also used to spatially interrogate the electrochemical activity of the diamond film using three redox systems: Ru(NH3)6+3/+2, Fe(CN)63-/4-, and IrCl62-/3-. Isolated regions of high electrochemical activity were found for all three systems, and interestingly, the active regions on a given thin-film electrode were different for each. It is concluded that current flow through this doped nanocrystalline film occurs through a fixed number of conductive sites and all of these sites appear to be electrochemically active for the redox systems tested. The results have important implications for understanding how boron-doped diamond functions as an electrochemical electrode.

Electrochemical degradation of 17β-estradiol (E2) at boron-doped diamond (Si/BDD) thin film electrode

Electrochemical degradation of aqueous solutions containing 17β-estradiol (E2), concentrations range of 250–750 μg dm −3, has been extensively studied using boron-doped diamond (BDD) anode with a working solution volume of 250 ml under galvanostatic control. Cyclic voltammetric experiments were performed to examine the redox response of E2 as a function of cycle number. The effect of operating variables such as initial concentration of E2, applied current density, supporting medium (Na 2SO 4, NaNO 3, and NaCl) and initial pH of the electrolyte (pH 2–10) were systematically examined and discussed. Electrolysis at high anodic potential causes complex oxidation of E2 that leads to form the final sole product as CO 2. A pseudo first-order kinetics for E2 decay was found against varying applied current density. Also, kinetic analysis suggests that electrooxidation reaction of E2 undergo the control of applied current density. It was observed that electrolyte pH and supporting medium have a vital role on E2 degradation. From a comparison study with other anode materials such as platinum (Pt) and glassy carbon (GC), the superiority of the BDD anode was proved. Total organic carbon results have shown that almost complete mineralization could be accomplished at higher applied current density with specific electrical charge 22.5 × 10 −2 A h dm −3. Mineralization current efficiency was comparatively lower with increasing applied current density.

Deposition of clusters and nanoparticles onto boron-doped diamond electrodes for electrocatalysis

Metal and metal oxide particles and nanoparticles, differing from each other by their nature and synthesis technique, were deposited onto boron-doped diamond (BDD) thin film electrodes. The applicability in electrocatalysis of thermally decomposed IrO2 and Au nanoparticles, electrodeposited Pt particles, dendrimer-encapsulated Pt nanoparticles (Pt DENs) and microemulsion-synthesized Pt/Ru nanoparticles was studied, once deposited on BDD substrate. In all cases, the electrochemical response of the composite electrodes could be solely attributed to the supported particles. All the particles, with the exception of Pt DENs, exhibited electrocatalytic activity. Pt DENs inactivity has been attributed to insufficient removal of the dendrimer polymer matrix. It was concluded that the BDD electrode is a suitable substrate for the electrochemical investigation of supported catalytic nanoparticles.

A comparison of boron-doped diamond thin-film and Hg-coated glassy carbon electrodes for anodic stripping voltammetric determination of heavy metal ions in aqueous media

The performance of boron-doped diamond (BDD) for the anodic stripping voltammetric (ASV) determination of heavy metal ions (Zn 2+, Cd 2+, Pb 2+, Cu 2+, Ag +) was compared with that of Hg-coated glassy carbon (Hg-GC). Hg has historically been the electrode of choice for ASV but there is an ongoing search for alternate electrodes and diamond is one of these. Despite the fundamentally different nature of the metal reduction and oxidation reactions on these two electrodes, BDD provides as good or superior analytical detection figures of merit when compared to Hg. The stripping peak potentials for all the metals studied were similar at both electrodes indicating that BDD is as active as Hg for metal phase formation and oxidation. Due to the more heterogeneous chemical and electrical properties across the BDD surface, the stripping peaks were broader and more asymmetric than they were for Hg-GC. The linear dynamic range for BDD was three to four orders of magnitude ( r 2 > 0.995), similar to Hg-GC, but the sensitivity for BDD was three to five times lower. However, the lower background current and noise for BDD enabled detection limits as low as those seen for Hg-GC. The minimum concentration of each metal ion detectable (S/N ≥ 3) with BDD was in the mid to low ppb range (e.g., 50 ppb Zn 2+, 1.0 ppb Cd 2+, 5.0 ppb Pb 2+, 10 ppb Cu 2+ and 1.0 ppb Ag +). BDD exhibited an electrode-to-electrode and run-to-run variability of less than 5%, which is comparable to that for Hg-GC. The possibility of incomplete metal oxidation and metal phase detachment from BDD was investigated using double step chronoamperometry. Neither of these processes was found to occur to any appreciable extent. The results demonstrate that BDD is a viable alternate electrode to Hg for ASV.

Pulsed Amperometry for Anti-fouling of Boron-doped Diamond in Electroanalysis of β-Agonists: Application to Flow Injection for Pharmaceutical Analysis

This work presents the construction and application of boron-doped diamond(BDD) thin film electrode as sensor for the determination of three β-agonists, viz.salbutamol, terbutaline and clenbuterol. Although well-known as a chemically inertmaterial, BDD film however shows fouling in detection of these compounds using fixedpotentialmode amperometry. A suitable waveform for pulsed amperometric detection(PAD) was developed and used to determine the agonist compounds. It was seen that thedeveloped PAD significantly refreshed the BDD surface for long-term detection in flowinjection analysis. Linear working ranges were 0.5-100 μM, 1.0-100 μM and 0.5-50 μM forsalbutamol, terbutaline and clenbuterol, respectively. The developed PAD-BDD system wasapplied to successfully determine salbutamol and terbutaline in commercial pharmaceuticalproducts. The methods were validated with a capillary electrophoresis method.

Cost-Effective Flow Cell for the Determination of Malachite Green and Leucomalachite Green at a Boron-Doped Diamond Thin-Film Electrode

An electrooxidation and a cost-effective flow-based analysis of malachite green (MG) and leucomalachite green (LMG) were investigated at a boron-doped diamond thin-film (BDD) electrode. Cyclic voltammetry as a function of the pH of the supporting electrolyte solution was studied. Comparison experiments were performed with a glassy carbon electrode. A well-defined cyclic voltammogram, providing the highest peak current, was obtained when using phosphate buffer at pH 2. The potential sweep-rate dependence of MG and LMG oxidation (peak currents for 1 mM MG and LMG linearly proportional to v 1/2, within the range of 0.01 to 0.3 V/s) indicates that the oxidation current is a diffusion-controlled process on the BDD surface. In addition, hydrodynamic voltammetry and amperometric detection using the BDD electrode combined with a flow injection analysis system was also studied. A homemade flow cell was used, and the results were compared with a commercial flow cell. A detection potential of 0.85 V was selected when using a commercial flow cell, at which MG and LMG exhibited the highest signal-to-background ratios. For the homemade flow cell, a detection potential of 1.1 V was chosen because MG and LMG exhibited a steady response. The flow analysis results showed linear concentration ranges of 1-100 microM and 4-80 microM for MG and LMG, respectively. The detection limit for both compounds was 50 nM.

Use of nickel implanted boron-doped diamond thin film electrode coupled to HPLC system for the determination of tetracyclines

The electrochemical analysis of tetracyclines was investigated using nickel-implanted boron-doped diamond thin film electrode (Ni-DIA) by cyclic voltammetry and high performance liquid chromatographic with amperometry. Cyclic voltammetry was used to study the electrochemical oxidation of tetracyclines. Comparison experiments were carried out utilizing as-deposited BDD and glassy carbon electrodes. Ni-DIA electrode provided well-resolved oxidative irreversible cyclic voltammograms and the highest current signals among the electrode studied. High performance liquid chromatography (HPLC) with amperometric detection was also studied. The chromatography was performed using a commercially available Inertsil C18 column, with the mobile phase being: 80% phosphate buffer (pH 2.5)–20% acetonitrile and detected at 1.55 V. The methods were validated over the concentration range 0.05–100 ppm with the overall average recoveries from 83.3 to 102.5% and R.S.D. of less than 10%. The proposed method was further applied to analyse shrimp samples.

Electroanalysis of Tetracycline Using Nickel-implanted Boron-doped Diamond Thin Film Electrode Applied to Flow Injection System

The electrochemical analysis of tetracycline was investigated using nickel-implanted boron-doped diamond thin film electrode by cyclic voltammetry and amperometry with a flow injection system. Cyclic voltammetry was used to study the electrochemical oxidation of tetracycline. Comparison experiments were carried out using as-deposited boron-doped diamond thin film electrode (BDD). Nickel-implanted boron-doped diamond thin film electrode (Ni-DIA) provided well-resolved oxidation irreversible cyclic voltammograms. The current signals were higher than those obtained using the as-deposited BDD electrode. Results using nickel-implanted boron-doped diamond thin film electrode in flow injection system coupled with amperometric detection are presented. The optimum potential for tetracycline was 1.55 V versus Ag/AgCl. The linear range of 1.0 to 100 microM and the detection limit of 10 nM were obtained. In addition, the application for drug formulation was also investigated.

Analysis of Tetracycline Antibiotics Using HPLC with Pulsed Amperometric Detection

The analysis of tetracycline, oxytetracyline, chlortetracycline and doxycycline by high-performance liquid chromatography with pulsed amperometric detection using an anodized boron-doped diamond thin film (BDD) electrode is originally reported. The analyses were carried out using the mobile phase, phosphate buffer (0.01 M, pH 2.5)-acetonitrile (80:20; v/v), on a C18 column (250 x 4.6 mm i.d., 5 microm) at a flow rate of 1.0 mL/min. The optimal PAD waveform parameters at the anodized BDD were 1.5 V (versus Ag/AgCl) detection potential (E(det)) for 290 ms (200 ms delay time and 90 ms integration time), 2.0 V (versus Ag/AgCl) oxidation potential (E(oxd)) for 200 ms oxidation time (t(oxd)) and 0.4 V (versus Ag/AgCI) reduction potential (E(red)) for 200 ms reduction time (t(red)). The proposed method showed the simultaneous determination of tetracycline, oxytetracyline, chlortetracycline and doxycycline with a linear range of 0.1 - 100 microg/mL, detection limits of 0.05 - 0.1 microg/mL and recoveries of 70.8 - 96.0%. The application of this method to real samples was demonstrated and validated using a shrimp sample.

Electroanalysis of lincomycin using boron-doped diamond thin film electrode applied to flow injection system

The electroanalysis of lincomycin was investigated using boron-doped diamond thin film (BDD) electrodes. First, the electrochemistry of lincomycin was studied by cyclic voltammetry as a function of pH of the solution, scan rate and the concentration of lincomycin. Comparison experiments were carried out using glassy carbon electrode. Boron-doped diamond thin film electrode provided well-resolved oxidation irreversible cyclic voltammogram. It was found that the peak position was 1.2 V (versus Ag/AgCl reference electrode). Second, the amperometric detection with BDD electrode was coupled with the flow injection analysis for the determination of lincomycin. The linear range of 0.5–125 μM and the detection limit of 0.02 μM were obtained. The percent recovery was shown in a range of 96–103. This purposed method was also applied to a drug formulation sample. It was found that the results (293 mg mL −1) were comparable to those labeled (300 mg mL −1).

Preparation of boron-doped semiconducting diamond films using BF 3 and the electrochemical behavior of the semiconducting diamond electrodes

Boron-doped semiconducting diamond films were prepared using BF 3 by microwave plasma assisted chemical vapor deposition. B-doping was confirmed by SIMS and Raman spectroscopic measurements and the B-doping levels were estimated. Electrochemical behaviors of boron-doped diamond thin-film electrodes prepared using B 2H 6 and BF 3 were studied by measuring cyclic voltammograms for anodic oxidation of 1,4-difluorobenzene in the liquid electrolyte, neat Et 4NF·4HF. The results of the direct thermal interaction of elemental fluorine with hydrogenated and oxidized diamond surfaces are also presented.

A flow injection method for the analysis of tetracycline antibiotics in pharmaceutical formulations using electrochemical detection at anodized boron-doped diamond thin film electrode

A method using flow injection (FI) with amperometric detection at anodized boron-doped diamond (BDD) thin films has been developed and applied for the determination of tetracycline antibiotics (tetracycline, chlortetracycline, oxytetracycline and doxycycline). The electrochemical oxidation of the tetracycline antibiotics was studied at various carbon electrodes including glassy carbon (GC), as-deposited BDD and anodized BDD electrodes using cyclic voltammetry. The anodized BDD electrode exhibited well-defined irreversible cyclic voltammograms for the oxidation of tetracycline antibiotics with the highest current signals compared to the as-deposited BDD and glassy carbon electrodes. Low detection limit of 10 nM (signal-to-noise ratio = 3) was achieved for each drug when using flow injection analysis with amperometric detection at anodized BDD electrodes. Linear calibrations were obtained from 0.1 to 50 mM for tetracycline and 0.5–50 mM for chlortetracycline, oxytetracycline and doxycycline. The proposed method has been successfully applied to determine the tetracycline antibiotics in some drug formulations. The results obtained in percent found (99.50–103.01%) were comparable to dose labeled.

Effect of sp2-Bonded Nondiamond Carbon Impurity on the Response of Boron-Doped Polycrystalline Diamond Thin-Film Electrodes

The physical and electrochemical properties of boron-doped polycrystalline diamond thin-film electrodes, prepared with varying levels of -bonded nondiamond carbon impurity, were systematically investigated. This impurity was introduced through adjustment of the methane-to-hydrogen (C/H) source gas ratio used for the deposition. Volumetric gas ratios of 0.3, 0.5, 1, 2, 3, and 5% were employed. Proportional increases in the fraction of grain boundary, the extent of secondary nucleation, and the -bonded carbon impurity content resulted in increasing C/H ratio. Variations in the morphology and microstructure were monitored using atomic force microscopy (AFM) and Raman spectroscopy, respectively. The electrode response was assessed using and 4-tert-butylcatechol (4-tBC). All were 1 mM in concentration and dissolved in either 1 M KCl or 0.1 M While increased -bonded carbon content had little effect on the cyclic voltammetric peak separation and peak current for the first two redox systems, the impurity had a significant impact on the latter two, as decreased proportionally with increased -bonded carbon content. The effect of the impurity on the reduction of oxygen in 0.1 M and 0.1 M NaOH was also investigated. A direct correlation was found between the relative amount of the impurity, as estimated from Raman spectroscopy, and the overpotential for oxygen reduction. The greater the nondiamond content, the lower the kinetic overpotential for the reduction reaction. Tafel plots yielded an apparent exchange current density that increased and a transfer coefficient that decreased with the increased nondiamond carbon content. The results demonstrate that the grain boundaries, and the carbon impurity presumably residing there, can have a significant impact on the electrode reaction kinetics for certain redox systems and little influence for others. © 2004 The Electrochemical Society. All rights reserved.

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.

Flow-injection determination of iodide ion in nuclear emergency tablets, using boron-doped diamond thin film electrode

The electrochemical determination of iodide was studied at boron-doped diamond thin film electrodes (BDD) using cyclic voltammetry (CV) and flow-injection (FI) analysis, with amperometric detection. Cyclic voltammetry of iodide was conducted in a phosphate buffer pH 5. Experiments were performed using glassy carbon (GC) electrode as a comparison. Well-defined oxidation waves of the quasi-reversible cyclic voltammograms were observed at both electrodes. Voltammetric signal-to-background ratios (S/B) were comparable. However, the GC electrode gives much greater in the background current as usual. The potential sweep rate dependence exhibited that the peak current of iodide oxidation at 1 mM varied linearly ( r 2 = 0.998) with the square root of the scan rate, from 0.01 to 0.30 V s −1. This result indicates that the reaction is a diffusion-controlled process with negligible adsorption on BDD surface, at this iodide concentration. Results of the flow-injection analysis show a highly reproducible amperometric response. The linear working range was observed up to 200 μM ( r 2 = 0.999). The detection limit, as low as 0.01 μM (3 σ of blank), was obtained. This method was successfully applied for quantification of iodide contents in nuclear emergency tablets.

Electrochemical Treatment of 4-Nitrophenol-Containing Aqueous Wastes Using Boron-Doped Diamond Anodes

The electrochemical oxidation of aqueous wastes containing 4-nitrophenol (4-NP) using a boron-doped diamond thin-film electrode has been studied. Within the parameter ranges used (150−4000 mg of 4-NP dm-3, pH 2−12, 30−60 mA cm-2, 25−60 °C), the complete treatment of the organic waste was achieved. The maximum current efficiencies were obtained under kinetic control. On the basis of the results of voltammetric and galvanostatic electrolysis studies, a simple mechanistic model was proposed. The first stage in the treatment of 4-NP-containing aqueous wastes is the release of the nitro group from the aromatic ring. As a consequence, phenol or quinones are formed. These organic compounds are oxidized first to carboxylic acids (maleic and oxalic) and later to carbon dioxide. On the cathode, the reduction of the 4-NP to 4-aminophenol takes place. In alkaline media, this compound can be polymerized and transformed into a dark brown solid.

Electrochemical Incineration of Organic Pollutants on Boron-Doped Diamond Electrode. Evidence for Direct Electrochemical Oxidation Pathway

The electrochemical incineration of organic pollutants on a boron-doped diamond (BDD) thin film electrode was examined by bulk electrolysis, and the mechanism of oxidation was investigated. A compa...

Detection of Ascorbic Acid in an Ethanol–Water Mixed Solution on a Conductive Diamond Electrode

Abstract Conductive boron-doped diamond thin-film electrodes have been shown to be highly suitable as electrochemical detectors in flow injection analysis (FIA) due to the lack of electrode deactivation due to fouling and the ability to withstand highly positive electrochemical potentials. In the present work, a diamond electrode was applied to the detection of ascorbic acid (AA) in an alcohol–water mixed solution. During FIA of AA in an ethanol (EtOH)–water solution including 0.1 M NaClO4, the interference from EtOH oxidation that would have been observed with a Pt electrode was avoided, and the amperometric response for AA was observed with the use of a conductive diamond as the electrode material. Moreover, The detection limit for AA that could be observed was lower than that for a glassy carbon electrode, because diamond exhibits a lower background current, smaller background noise, and smaller injection noise. These findings suggest that the diamond electrode may be applied in the detection of other redox-active impurities and added substances in alcohol or alcohol–water solutions, such as chlorophyll, nicotinamide, caffeine, riboflavin, and dl-α-tocopherol.

Gradient liquid chromatography of leucine-enkephalin peptide and its metabolites with electrochemical detection using highly boron-doped diamond electrode

Boron-doped diamond thin film (BDD) electrodes have been used to study the oxidation reactions and to detect leucine-enkephalinamide (LEA) and its metabolites, tyrosine (T), tyrosyl-alanine (TA), tyrosyl-alanine-glycine (TAG) and leucine-enkephalin (LE) using cyclic voltammetry (CV), flow-injection analysis (FIA), and gradient liquid chromatography (LC) with amperometric detection. At diamond electrodes, well-defined and highly reproducible cyclic voltammograms were obtained with signal-to-background ( S/ B) ratios 5–10 times higher than those observed for glassy carbon (GC) electrodes. The analytical peaks of LC for LEA and its metabolites were well resolved. No deactivation of BDD electrodes was found after several experiments with standard as well as plasma samples, indicating high stability of the electrode. Calibration curves were linear over a wide range from 0.06 to 30 μ M with regression coefficients of 0.999 for all compounds. The limits of detection obtained based on a signal-to-noise ratio of 3:1 were 3, 2.2, 2.7, 20 and 11 n M for T, TA, TAG, LE and LEA, respectively. These values were at least one order lower than those obtained at GC electrodes, which has given limits of detection of 22.88, 20.64, 89.57, 116.04 and 75.67 for T, TA, TAG, LE and LEA, respectively. Application of this method to real samples was demonstrated and validated using rabbit serum samples. This work shows the promising use of conducting diamond as an amperometric detector in gradient LC, especially for the analysis of enkephalinamide and its metabolites.

Electron Transfer Kinetics of Ferrocene at Microcrystalline Boron‐Doped Diamond Electrodes: Effect of Solvent and Electrolyte

AbstractCyclic voltammetric measurements were made using well‐characterized microcrystalline boron‐doped diamond thin‐film electrodes to test the material's responsiveness for ferrocene as a function of scan rate, solvent, and electrolyte composition. Apparent heterogeneous electron transfer rate constants, k°app, of 0.042±0.015, 0.048±0.015, and 0.008±0.002 cm/s were observed in 0.1 M NaClO4/CH3CN, 0.1 M TBAClO4/CH3CN, and 0.1M TBAClO4/CH2Cl2, respectively. These rate constants, obtained using electrodes without any type of pretreatment, are similar to those observed for freshly polished glassy carbon. The results demonstrate that boron‐doped diamond is a viable material for the electrochemical analysis of nonaqueous analytes.