Hydrogen-terminated Boron-doped Diamond Research Articles

Study of Quinine Hydrochloride Detection Using Boron-Doped Diamond Electrodes

This study investigates the electrochemical properties of quinine hydrochloride (QH) using boron-doped diamond (BDD) electrodes. The redox behavior of QH was analyzed and compared in phosphate buffer solution (PBS) and potassium perchlorate (KClO4) electrolyte, observing an increase in current response with hydrogen-terminated BDD (H-BDD) electrodes. A cyclic voltammogram of QH in 0.1M PBS and 0.1M KClO4 shows a reduction peak at -1.14V (vs. Ag/AgCl). The scan rate dependence was examined to understand the reduction mechanism involving two electrons. A linear calibration curve was noted from 2μM to 25μM range (R2 = 0.99) with detection limits of 0.18μM in PBS and 0.16μM in KClO4. The BDD electrodes demonstrated good selectivity in tonic water with sharp oxidation potentials for QH, confirming their stability for QH detection.

Electrochemical reduction of nitrate on boron-doped diamond electrodes: Effects of surface termination and boron-doping level

This study is among the first to systematically study the electrochemical reduction of nitrate on boron-doped diamond (BDD) films with different surface terminations and boron-doping levels. The highest nitrate reduction efficiency was 48% and the highest selectivity in the production of nitrogen gas was 44.5%, which were achieved using a BDD electrode with a hydrogen-terminated surface and a B/C ratio of 1.0%. C–H bonds served as the anchor points for attracting NO3− anions close to the electrode surface, and thus accelerating the formation of NO3−(ads). Compared to oxygen termination, hydrogen-terminated BDD exhibited higher electrochemical reactivity for reducing nitrate, resulting from the formation of shallow acceptor states and small interfacial band bending. The hydrophobicity of the hydrogen-terminated BDD inhibited water electrolysis and the subsequent adsorption of atomic hydrogen, leading to increased selectivity in the production of nitrogen gas. A BDD electrode with a boron-doping level of 1.0% increased the density of acceptor states, thereby enhancing the conductivity and promoting the formation of C–H bonds after the cathodic reduction pretreatment leading to the direct reduction of nitrate.

Electrochemically modified boron-doped diamond electrode with Pd and Pd-Sn nanoparticles for ethanol electrooxidation

The modification of hydrogen terminated boron-doped diamond (HBDD) electrode with pure palladium (Pd) and Pd-Sn (tin) nanoparticles is described in this study. For synthesis of Sn/HBDD and Pd-Sn/HBDD electrode, a potentiostatic two-step electrochemical method involving the electrodeposition of Sn followed by Pd was used, respectively. The modification of the HBDD electrode with Sn and noble metal Pd by forming bimetallic Pd-Sn nanoparticle leads to a higher electrocatalytic activity. The electrocatalytic activity of the bimetallic Pd-Sn nanoparticles was evaluated towards the electrooxidation of ethanol in alkaline media and compared with that of the Pd nanoparticles alone. The bimetallic Pd-Sn nanoparticles modified HBDD electrode exhibits higher current densities and less poisoning effects during ethanol electrooxidation compared to Pd/HBDD. The proper tuning of the Pd loading on a foreign metal along with the surface termination effects of the BDD electrode plays a crucial role in achieving a high mass (4.26×106mA/g) and specific (12.37mA/cm2) electrocatalytic activity of Pd towards ethanol electrooxidation. The aforementioned catalysts of this research possess a high poisoning resistance (If/Ib=1.63) and stability towards ethanol electrooxidation in alkaline media.

Polycrystalline boron-doped diamond with an oxygen-terminated surface channel as an electrolyte-solution-gate field-effect transistor for pH sensing

A polycrystalline boron-doped diamond (BDD) electrolyte solution-gate field effect transistor (SGFET) for use as a pH sensor was developed. The polycrystalline diamond films with a boron-doped layer possessed semiconducting properties that were comparable to hydrogen-terminated non-doped diamond. The hydrogen-terminated BDD surface was successfully transferred to a partially oxygen-terminated surface by ozone exposure, and its SGFET current–voltage (I–V) characteristics were evaluated with bias voltages within the potential window of diamond. The drain-source current(Ids)–drain-source voltage(Vds) characteristics showed pinch-off and saturation. In addition, they stably operated in electrolyte solutions with pH values from 2 to 12. The transfer characteristics exhibited a pH sensitivity of approximately 30mV/pH, which is comparable with the pH sensitivity of the conventional oxygen-terminated non-doped SGFET and the single-crystal BDD SGFET investigated in our previous work. Furthermore, the BDD SGFET exhibited improved long-term stability, and the coefficient of variation (CV) of Ids for 10 months was up to 10%.

Accurate determination of the valence band edge in hard x-ray photoemission spectra using GW theory

We introduce a new method for determining accurate values of the valence-band maximum in x-ray photoemission spectra. Specifically, we align the sharpest peak in the valence-band region of the experimental spectrum with the corresponding feature of a theoretical valence-band density of states curve from ab initio GW theory calculations. This method is particularly useful for soft and hard x-ray photoemission studies of materials with a mixture of valence-band characters, where strong matrix element effects can render standard methods for extracting the valence-band maximum unreliable. We apply our method to hydrogen-terminated boron-doped diamond, which is a promising substrate material for novel solar cell devices. By carrying out photoemission experiments with variable light polarizations, we verify the accuracy of our analysis and the general validity of the method.

Surface Modification of Boron-Doped Diamond with Microcrystalline Copper Phthalocyanine: Oxygen Reduction Catalysis.

Surface modification of boron-doped diamond (BDD) with copper phthalocyanine was achieved using a simple and convenient dropcast deposition, giving rise to a microcrystalline structure. Both unmodified and modified BDD electrodes of different surface terminations (namely hydrogen and oxygen) were compared via the electrochemical reduction of oxygen in aqueous solution. A significant lowering of the cathodic overpotential by about 500 mV was observed after modification of hydrogen-terminated (hydrophobic) diamond, while no voltammetric peak was seen on modified oxidised (hydrophilic) diamond, signifying greater interaction between copper phthalocyanine and the hydrogen-terminated BDD. Oxygen reduction was found to undergo a two-electron process on the modified hydrogen-terminated diamond, which was shown to be also active for the reduction of hydrogen peroxide. The lack of a further conversion of the peroxide was attributed to its rapid diffusion away from the triple phase boundary at which the reaction is expected to exclusively occur.

Electrochemical determination of bisphenol A using a boron-doped diamond electrode

An electrochemical method was developed for the determination of bisphenol A (BPA) at an unmodified boron-doped diamond (BDD) electrode using differential pulse voltammetry (DPV). The sensitivity of the DPV measurements was significantly improved by using a predominantly hydrogen-terminated BDD electrode obtained by a cathodic pretreatment. A highly linear analytical curve was obtained for BPA determination in the range of 0.44–5.2μmolL−1, with quantification and detection limits of 0.71μmolL−1 and 0.21μmolL−1, respectively. After assuring that the results obtained with the developed DPV method did not change in the presence of possible interferents, the method was successfully applied to monitor the concentration of BPA as it was electrooxidized in a flow reactor with an Nb/BDD anode. As far as it could be verified, the proposed electroanalytical method is the first one based on the use of an unmodified electrode.

Sensitive Electrochemical Detection of Glucose at Glucose Oxidase-Cobalt Phthalocyanine-Modified Boron-Doped Diamond Electrode

Electrochemical detection of glucose was achieved at a glucose oxidase (GOx)-cobalt phthalocyanine (CoPc)-modified boron-doped diamond (BDD) electrode without any additional electron mediator in the electrolyte solution. The surface of the hydrogen-terminated BDD thin film prepared by microwave plasma-assisted CVD was modified with 4-vinylpyridine (4VP) via photochemical modification. The 4VP-BDD was then immersed in a CoPc solution to obtain CoPc-BDD. A poly(p-phenylenediamine) (PPD) thin film containing GOx was coated on the CoPc-BDD electrode surface via electropolymerization. At the GOx/PPD-CoPc-BDD electrode, anodic current for glucose oxidation was observed with a sigmoidal voltammetric curve, indicating successful electron mediation of H2O2generated as the result of glucose oxidation at GOx. The signal-to-background ratio for voltammetric current of glucose detection was larger at the GOx/PPD-CoPc-BDD electrode than at the GOx/PPD-modified platinum electrode due to the smaller background current of the modified BDD electrode.

Electrochemical detection of surfactant cetylpyridinium bromide using boron-doped diamond as electrode

An octanethiolate gold particle modified boron-doped diamond (OT-Au-BDD) electrode has been developed for the determination of a surfactant, cetylpyridinium bromide (CPB) with K 3Fe(CN) 6 as a probe. The gold nanoparticles were first deposited on the hydrogen-terminated boron-doped diamond (BDD) surface with electrochemical method and producing gold particle modified BDD (Au-BDD). The octanethiol was subsequently self-assembled onto the Au-BDD surface to form the OT-Au-BDD electrode. The prepared electrode gave a linear response range of 5 × 10 − 7 –10 − 4 M and a detection limit of 0.2 μM to cetylpyridinium bromide, it also displayed better reproducibility and stability than the self-assembled octanethiol monolayer modified gold (OT-Au) electrode due to the outstanding electrochemical properties of BDD.

A novel multicommutation stopped-flow system for the simultaneous determination of sulfamethoxazole and trimethoprim by differential pulse voltammetry on a boron-doped diamond electrode

A method based on a multicommutation stopped-flow system was developed and applied in the simultaneous determination of sulfamethoxazole (SMX) and trimethoprim (TMP) in pharmaceutical formulations by differential pulse voltammetry (DPV) using a cathodically pre-treated hydrogen-terminated boron-doped diamond (HT-BDD) electrode. The obtained analytical curves were linear from 1.0 to 8.0 mg L−1 and 0.20 to 1.6 mg L−1 for SMX and TMP, respectively. The calculated LOD and LOQ values for SMX were 16.5 μg L−1 and 55.1 μg L−1 (or 65.1 nmol L−1 and 218 nmol L−1), respectively; for TMP, they were 18.3 μg L−1 and 61.1 μg L−1 (or 63.0 nmol L−1 and 210 nmol L−1), respectively. The optimization and application of the multicommutation stopped-flow system in the simultaneous electrochemical determination of SMX and TMP by DPV on the HT-BDD electrode yielded an excellent sample throughput (30 h−1). Addition and recovery studies indicated that the matrix effect did not present any significant interference in the determinations. Thus, the proposed method was successfully applied in the determination of SMX and TMP in two different commercial pharmaceutical formulations with results similar (at 95% confidence level) to those obtained using the USP method (HPLC). The obtained performance allowed concluding that the proposed method is quite advantageous and that its total automation can lead to rapid, sensitive, precise, and accurate results, with an excellent sample throughput.

The electron transfer behavior of the hydrogen-terminated boron-doped diamond film electrode

To clarify the electron transfer behavior of the hydrogen-terminated boron-doped diamond film electrode in an electrolytic solution, its detailed electronic structures were investigated by using scanning probe microscopy and ab initio methods. The interface structure of the hydrogen-terminated diamond electrode and the electrolyte was also studied by means of cyclic voltammetry and AC impedance spectroscopy. The results showed that there exist shallow acceptors in the band gap of the hydrogenated diamond films. Neither the surface hydrogen alone nor the subsurface hydrogen could induce the shallow acceptors, though they interact strongly with the surface carbon atoms or subsurface carbon and boron atoms in the diamond film. It is the interaction of the surface adsorbates and the surface C–H bonding that gives rise to the shallow acceptors in the band gap of the hydrogenated diamond film. The surface shallow acceptors in the band gap of the hydrogenated diamond film could lower the energy barrier of the electron transfer between the diamond electrode and the electrolytic solution. Thus, electrochemical window for the hydrogenated diamond film is narrower and, its film resistance and capacitance are also smaller than those of the oxygenated one. In our work, the experimental data obtained by using scanning probe microscopy are in good agreement with the calculation results.

Photochemical Modification of a Boron-doped Diamond Electrode Surface with Vinylferrocene

Boron-doped diamond (BDD) surfaces were photochemically modified with vinylferrocene (VFC), and the modified surfaces were analyzed both qualitatively and quantitatively by electrochemical techniques. VFC-modified BDD (VFC-BDD) was prepared by ultraviolet (254 nm) irradiation of hydrogen-terminated BDD in mesitylene, acetonitrile, or n-alkane solutions of VFC. Cyclic voltammetry (CV) results indicated facile electron transfer between ferrocenyl groups and the BDD substrate. The surface coverage of VFC-modified polycrystalline and single-crystal (100) BDD was also estimated by CV and was found to reach saturation at a value possibly corresponding to monolayer coverage by ferrocenyl groups. The electrochemical stability of VFC-BDD to successive potential cycling in acetonitrile was found to be much higher than that of a self-assembled ferrocenylalkanethiol monolayer on an Au electrode surface. This study is the first to show that appropriate solutions of a terminal alkene can be used in the photochemical modification of diamond, yielding monolayer coverage of the surface.

Influence of the surface termination on the electrochemical properties of boron-doped diamond (BDD) interfaces

The paper reports on the electrochemical study of heavily boron-doped diamond (BDD) in aqueous media. Cyclic voltammetry and Mott-Schottky analysis were used to evaluate the influence of the surface termination on the electrochemical properties of BDD electrodes. The behavior of aminated BDD (NH 2–BDD) interfaces, prepared from hydrogen-terminated BDD using NH 3 plasma and from photochemically oxidized BDD (HO–BDD) using 3-aminopropyltrimethoxysilane (APTMES), are investigated and compared to those of H–BDD and HO–BDD. While H–BDD and HO–BDD electrodes show classical semiconductor behavior, amine-terminated BDD interfaces exhibit metallic behavior at pH < 10 and a semiconductor behavior at more basic pH.

Solvent-free chemical functionalization of hydrogen-terminated boron-doped diamond electrodes with diazonium salts in ionic liquids

This paper reports on green chemical functionalization of hydrogen-terminated boron-doped diamond (BDD) surfaces with aryldiazonium salts in the presence of ionic liquids. The reaction takes place at room temperature in air without any external bias in either hydrophobic (1-butyl-3-methylimidazolium hexafluorophosphate) or hydrophilic (1-butyl-3-methylimidazolium methyl sulfate) ionic liquids. The resulting surfaces were characterized using X-ray photoelectron spectroscopy and electrochemical measurements.

Anodic Deposition of RuOx ∙ nH2O at Conductive Diamond Films and Conductive Diamond Powder for Electrochemical Capacitors

Cyclic voltammetry was used in order to directly deposit hydrous ruthenium oxide on conductive diamond substrates. It was found that, at the hydrogen-terminated boron-doped diamond (BDD) surface, the overall deposition process is rather slow compared to the case of metal substrates. Nevertheless, the values estimated for the specific charge and specific capacitance by cyclic voltammetric and chronopotentiometric experiments, respectively, compare favorably to those reported in the literature. Additional advantages of using a BDD support are the excellent stability of the response, the extreme robustness even under severe functioning conditions, and, importantly, negligible substrate effects. It was also observed that deposition at a BDD powder surface greatly enhanced both the specific charge and the specific capacitance. These features strongly recommend the use of conductive diamond powder as a substrate for hydrous ruthenium oxide, particularly in view of possible electrochemical capacitor applications.

Peptide Immobilization on Amine-Terminated Boron-Doped Diamond Surfaces

This paper reports on the formation and characterization of semicarbazide termination on aminated boron-doped diamond (BDD) surfaces, and further preparation of peptide microarray through site-specific alpha-oxo semicarbazone ligation. Hydrogen-terminated BDD electrodes were first aminated using NH3 plasma treatment and then reacted with triphosgene and Fmoc-protected hydrazine to yield a protected semicarbazide termination. Subsequent deprotection and chemical reaction with glyoxylyl peptides led to the covalent immobilization of the peptides on the surface through site-specific ligation. The resulting surfaces were characterized using X-ray photoelectron spectroscopy (XPS) and fluorescence measurements.

Surface Energy Band and Electron Affinity of Highly Phosphorous-doped Epitaxial CVD Diamond

The surface energy band diagrams and the electron affinity of hydrogen-terminated and oxygen-terminated highly phosphorous-doped single crystal diamond (111) surfaces have been studied by ultraviolet photoelectron spectroscopy, secondary electron spectroscopy, X-ray photoelectron spectroscopy and photoemission electron micro-spectroscopy. A hydrogen-terminated boron-doped diamond (001) surface was used as a reference of surface energy band diagram. The electron affinity of the H-terminated heavily P-doped diamond was determined to be 0.2 ± 0.15 eV, thus close to zero. The electron affinity of the O-terminated highly P-doped diamond was determined to be 0.0 ± 0.15 eV, thus can be negative. However, the surface energy bands for the two highly P-doped samples were found to have large amounts (3 eV) of upward bending toward surface. [DOI: 10.1380/ejssnt.2007.33]

Effect of electronic structures on electrochemical behaviors of surface-terminated boron-doped diamond film electrodes

In order to analyze the electrochemical behaviors of hydrogen-terminated and oxygen-terminated boron-doped diamond film electrodes, experiments of the cyclic voltammetry and AC impedance spectroscopy have been performed. For the purpose of clarifying the detailed electronic structures of these diamond films, current–voltage spectroscopy curves and XPS spectra have been investigated by scanning probe microscopy and X-ray photoelectron spectroscopy, respectively. For the hydrogen-terminated boron-doped diamond film electrode, its potential window is narrower than that of the oxygen-terminated boron-doped diamond. The impedance results indicate that the diamond film resistances and capacitances corresponding to different surface-terminated boron-doped diamond electrodes vary significantly. The surface band gap of hydrogen-terminated diamond film is narrow with empty surface states in it. In contrast, the surface band gap of oxygen-terminated diamond film is wide and clean. Compared with hydrogen-terminated diamond film, the surface energy bands of oxygen-terminated diamond film bend downwards. Based on their electronic structures, the electrochemical behaviors of the two boron-doped diamond film electrodes have been discussed.

Amperometric biosensor based on tyrosinase immobilized on a boron-doped diamond electrode

A novel method has been developed to immobilize tyrosinase onto the surface of boron-doped diamond (BDD) electrode. The hydrogen-terminated BDD (HBDD) surface was first functionalized by photochemically linking vinyl groups of allylamine, producing covalently linked amine-terminated active BDD (ABDD) surface. Then the tyrosinase was immobilized onto the ABDD surface by carbodiimide coupling reaction. The amperometric response was measured as a function of concentration of phenolic compounds in 0.1M phosphate buffer solution (pH 6.5). The tyrosinase-modified ABDD electrode gave a linear response range of 1-175, 1-200 and 1-200 microM and sensitivity of 80.0, 181.4 and 110.0 mA M(-1)cm(-2) for phenol, p-cresol, 4-chlorophenol, respectively. Moreover, selective detection of dopamine (DA) in the presence of ascorbic acid (AA) has been demonstrated with the tyrosinase-modified ABDD electrode. Linearity was observed within the range of 5-120 microM. The above enzyme electrode could maintain 90% of its original activity after intermittent use for 1 month when storing in a dry state at 4 degrees C.

Direct electrochemical detection of sodium azide in physiological saline buffers using highly boron-doped diamond electrodes

Direct detection of sodium azide was examined by using highly boron-doped diamond (BDD) electrodes in some physiological saline buffer solutions. Three important saline buffers, ADA buffer ( N-(2-acetamido) iminodiacetic acid), sodium EDTA and imidazole, were investigated. Hydrogen-terminated BDD was fixed for the investigation since it showed much better sensitivity for azide oxidation in comparison with the oxygen-terminated one. Wide range of buffer concentration was examined. A well-separated peak of sodium azide was observed in its mixture with the buffers, resulting in selective sodium azide detection. The current responses were exactly total addition of sodium azide and buffer current responses. The present method was evidenced to be available for direct detection of sodium azide in two samples of commercial diluents for cell counting. A standard addition method was applied. Sodium azide concentrations of 502 and 1355 μg mL −1 were detected in both samples with the R.S.D.s of 0.07 and 2.37%, respectively. Validation was achieved by the comparison with the sample concentrations given by the manufacturer. Simple, selective, good sensitivity and excellent reproducible detection make the diamond electrodes very attractive for numerous electroanalytical applications.