Boron-doped Nanocrystalline Diamond Electrodes Research Articles

Effect of Surface Oxygen on the Wettability and Electrochemical Properties of Boron-Doped Nanocrystalline Diamond Electrodes in Room-Temperature Ionic Liquids.

This paper reports on how the surface chemistry of boron-doped nanocrystalline diamond (BDD) thin-film electrodes (H vs O) affects the wettability and electrochemical properties in two room-temperature ionic liquids (RTILs): [BMIM][PF6] and [HMIM][PF6]. Comparative measurements were made in 0.5 mol L-1 H2SO4. The BDD electrodes were modified by microwave or radio-frequency (RF) plasma treatment in H2 (H-BDD), Ar (Ar-BDD), or O2 (O-BDD). These modifications produced low-, medium-, and high-oxygen surface coverages. Atomic O/C ratios, as determined by X-ray photoelectron spectroscopy (XPS), were 0.01 for H-BDD, 0.08 for Ar-BDD, and 0.17 for O-BDD. The static contact angle of ultrapure water on the modified electrodes decreased from 110° (H-BDD) to 41° (O-BDD) with increasing surface oxygen coverage, as expected as the surface becomes more hydrophilic. Interestingly, the opposite trend was seen for both RTILs as the contact angle increased from 20° (H-BDD) to 50° (O-BDD) with increasing surface oxygen coverage. The cyclic voltammetric background current and potential-dependent capacitance in both RTILs were largest for BDD electrodes with the lowest O/C ratio (H-BDD) and smallest contact angle. Slightly larger voltammetric background currents and capacitance were observed in [HMIM][PF6] than in [BMIM][PF6]. Capacitance values ranged from 8 to 16 μF cm-2 over the potential range for H-BDD and from 4 to 6 μF cm-2 for O-BDD. The opposite trend was observed in H2SO4 as the voltammetric background current and capacitance were largest for BDD electrodes with the highest O/C ratio (O-BDD) and smallest contact angle. In summary, reducing the surface oxygen on BDD electrodes increases the wettability to two RTILs and this increases the voltammetric background current and capacitance.

A Comparative Study on Electrochemical Treatment of Wastewater By Using BDD Electrodes with Different Sizes of Crystals

Boron doped diamond (BDD) electrode has been widely used in wastewater treatment, due to its wide potential windows, low background current, high stability and corrosion resistance [1]. Typical BDD electrode is always referred to microcrystalline diamond, which is mainly composed of sp3 carbon and has little sp2 carbon in the film [2]. Thus the electrochemical oxidation ability of this type of BDD electrode can be attributed to the effect of sp3 carbon. When the diamond grain size reduces to the degree of nanometer, its characteristics will certainly change. Nanocrystalline diamond film can be divided into two parts, named grain and grain boundary, grain is made of sp3 diamond, while grain boundary is mainly consist of sp2 carbon, including graphite, hydrocarbon and amorphous carbon et al [3]. The unique structure of the nanocrystalline diamond film makes it has many excellent properties, including high hardness, low surface roughness, high thermal conductivity and electron emission et al. Recently, many researchers try to focus on the study of the role of sp3/sp2 ratio on the influence of electrochemical oxidation efficiency. And they do have some discoveries. Araújo et al. studied the influence of sp3/sp2 ratio on the performance of electrochemical oxidation of Rhodamine B [4]. They found that higher diamond content in the film favored the greater TOC and COD removal rates as well as the oxidation of organic compounds to CO2. Souza et al. studied the effect of the sp3/sp2 ratio on the electrochemical oxidation of 2,4-dichlorophenoxyacetic acid [5]. They found that higher sp3/sp2 ratio would lead to a more rapid and efficient oxidation. Besides, they also found that with the increase of sp3 content in the film, the maximum concentration of chlorinated compounds would decrease. It has shown that sp2 content in the diamond film has significant influence on the performance of electrochemical oxidation. Thus, in this paper, comparative study of electrochemical oxidation of artificial humidity condensate and artificial human urine using boron doped nanocrystalline diamond electrode (BDNCD) and boron doped microcrystalline diamond electrode (BDMCD) respectively was carried out. TOC removal efficiency as well as the variation of the organic and inorganic compounds are investigated. Finally, the accelerated lifetime test was measured to comparison the lifetime of both electrodes. The results showed that the degradation rates were in good agreement with the pseudo first order kinetic model, with the degradation rate constant of 1.33h-1 and 1.02h-1 for BDMCD and BDNCD anode respectively. The degradation rate in BDMCD anode was 1.3 times faster than BDNCD anode, this was mainly due to different carbon phases in BDMCD and BDNCD electrode. BDMCD film was mostly composed of sp3 carbon, the concentration of sp2 carbon was negligible, while BDNCD film had a relatively large amount of sp2 carbon in grain boundary together with sp3 carbon in grain. It was found that NO2- and NO3- were the main intermediate products, and NO3- was the final product for two kinds of electrodes. Compared with BDMCD system, the oxidation of nitrogen compounds also show a lagging behind. In summary, both electrode had the same mineralization efficiency in the enough treatment time, but BDMCD anode has a higher degradation rate. That means high sp3 content in the film favors high degradation rate. The comparative study of the accelerated lifetime test of both electrodes showed that the lifetime of BDNCD electrode was 32.8% higher than BDMCD electrode. So it means high sp2 content in the film will lead to a higher lifetime of diamond electrode due the low surface roughness of electrode. Reference [1] Panizza M, Cerisola G., Journal of Electroanalytical Chemistry, 2010, 638(1): 28–32. [2] Guo L, Chen G., Diamond and Related Materials, 2007, 16(8): 1530–1540. [3] Williams O A., Diamond and Related Materials, 2011, 20(5-6): 621–640 [4] De Araújo D M, Cañizares P, Martínez-Huitle C A, et al., Electrochemistry Communications, 2014, 47: 37–40. [5] Souza F L, Saéz C, Lanza M R V, et al., Electrochimica Acta, 2016, 187: 119–124.

Thermal oxidation induced high electrochemical activity of boron-doped nanocrystalline diamond electrodes

Thermal oxidation treatment was executed on boron-doped nano-crystalline diamond (B-NCD) films to change both the microstructure and the terminal groups of grains and grain boundaries. Their contributions to the electrochemical activity and electrical properties were investigated. The grain boundaries become narrowing, with ordered graphite phase firstly, and then they become disordered for long time oxidized treatment. This causes that the mobility of the B-NCD electrodes increases to 84.97cm2/Vs after 30min oxidation and then it decreases obviously with oxidation time further increasing. Nanocrystalline diamond grains with high carrier concentration are growing larger and naked on the B-NCD electrode’s surface after oxidization. Also, part of the terminal CH groups on the grain phases turn to CO groups with positive electron affinity, which is prone to attract electrons from nearby anions. These results lead to larger electrochemical activity area with quick charge transfer rate in the surface of B-NCD electrode. The silane is used to shield the OH sites from electrochemical activity. The covered area become less with the oxidized time, further confirming that the electrochemical reaction mainly occurs on the grain phases and the OH groups is mainly growing in grain boundaries.

Diamond microelectrode arrays for in vitro neuronal recordings

A novel microfabrication technique for microelectrode arrays (MEAs) with a full diamond-cell interface is demonstrated. Boron-doped nano-crystalline diamond (BNCD) is used as a conductive electrode material on metal tracks insulated by intrinsic NCD. MEAs successfully recorded spontaneous electrical activity in rat primary cortical neuronal cultures. Patch-clamp measurements show no alterations to cell membrane passive properties or active firing response, for cell developing ex vivo on diamond. Impedance analysis revealed low impedance magnitude of BNCD electrodes, suitable for multi-unit neuronal recordings. Additionally, the impedance phase of the fabricated electrodes shows a high degree of capacitive coupling, ideal for neuron stimulation.

From micro to nanocrystalline boron doped diamond applied to cadmium detection

Cadmium detection was investigated by Square Wave Anodic Stripping Voltammetry (SWASV) measurements by using boron doped diamond electrodes with different morphologies from micro to nanocrocrystalline grains as Boron Doped Diamond (BDD) and Boron Doped Nanocrystalline Diamond (BDND), respectively. The argon concentrations, in the argon/hydrogen ratio, used were 0, 50, 60, 70, and 80vol.%. SWASV technique was applied in 4×10−4mol L−1 ammonium acetate buffer pH4.2. The peak currents were measured for Cd2+ concentration ranging from 1 to 20μgL−1. This change in film grain size and roughness affected how cadmium was deposited on the electrode surfaces, thus affecting its electroanalytical response from SWASV measurements as well as its selectivity. For all electrodes cadmium detection limits (DL) were lower than 1μgL−1 while for BDND electrode DL reached 0.016μgL−1. These values are lower than that required by the Brazilian Health Ministry for potable water (1μgL−1) and confirm that diamond electrodes are a suitable mercury-free method to determine cadmium trace levels in water. A strong correlation between the electrode selectivity and its grain size also confirmed the best performance of BDND electrode.

Boron-Doped Nanocrystalline Diamond Electrodes for Neural Interfaces: In vivo Biocompatibility Evaluation.

Boron-doped nanocrystalline diamond (BDD) electrodes have recently attracted attention as materials for neural electrodes due to their superior physical and electrochemical properties, however their biocompatibility remains largely unexplored. In this work, we aim to investigate the in vivo biocompatibility of BDD electrodes in relation to conventional titanium nitride (TiN) electrodes using a rat subcutaneous implantation model. High quality BDD films were synthesized on electrodes intended for use as an implantable neurostimulation device. After implantation for 2 and 4 weeks, tissue sections adjacent to the electrodes were obtained for histological analysis. Both types of implants were contained in a thin fibrous encapsulation layer, the thickness of which decreased with time. Although the level of neovascularization around the implants was similar, BDD electrodes elicited significantly thinner fibrous capsules and a milder inflammatory reaction at both time points. These results suggest that BDD films may constitute an appropriate material to support stable performance of implantable neural electrodes over time.

Electrochemical decolorization of dye wastewater by surface-activated boron-doped nanocrystalline diamond electrode

Complex organics contained in dye wastewater are difficult to degrade and often require electrochemical advanced oxidation processes (EAOPs) to treat it. Surface activation of the electrode used in such treatment is an important factor determining the success of the process. The performance of boron-doped nanocrystalline diamond (BD-NCD) film electrode for decolorization of Acid Yellow (AY-36) azo dye with respect to the surface activation by electrochemical polarization was studied. Anodic polarization found to be more suitable as electrode pretreatment compared to cathodic one. After anodic polarization, the originally H-terminated surface of BD-NCD was changed into O-terminated, making it more hydrophilic. Due to the oxidation of surface functional groups and some portion of sp2 carbon in the BD-NCD film during anodic polarization, the electrode was successfully being activated showing lower background current, wider potential window and considerably less surface activity compared to the non-polarized one. Consequently, electrooxidation (EO) capability of the anodically-polarized BD-NCD to degrade AY-36 dye was significantly enhanced, capable of nearly total decolorization and chemical oxygen demand (COD) removal even after several times of re-using. The BD-NCD film electrode favored acidic condition for the dye degradation; and the presence of chloride ion in the solution was found to be more advantageous than sulfate active species.

Effects of dynamic polarization on boron-doped NCD properties and on its performance for electrochemical-analysis of Pb (II), Cu (II) and Hg (II) in aqueous solution via direct LSV

Boron-doped diamond films electrode has been effectively applied in electroanalysis to detect numerous kinds of electroactive chemicals including heavy metals. The success of this application not only depends on the original quality of the films, but more than that, surface treatment or activation and analytical method applied play important role. Fabricated boron-doped nanocrystalline diamond (BD-NCD) in this work were electrochemically pretreated prior to the measurement of heavy metal ions in the solution. The surface properties of the films were evaluated with FE-SEM, AFM, Raman spectroscopy and XPS. The technique chosen for heavy metal measurement was linear sweep voltammetry (LSV) after comparing with differential pulse and square wave voltammetry. In this study, dynamic polarization applied on the BD-NCD electrode was proven to enhance its surface properties. The result of XPS analysis shows that polarized electrode exhibits diminution of Csp2 and possess minimum adventitious carbon content on its surface. This leads to an increase of electrode kinetic and promotes its capability for Pb, Cu and Hg ions measurements in the aqueous solution using LSV technique without pre-concentration step. The linearity of current response with increasing heavy metals concentration in an acetate buffer is ranging from 1 to 22.5 μM for Pb and Cu ions and 1 to 10 μM for Hg ion. The detection limit and sensitivity are 1.339, 0.102 and 0.666 μM, and 0.014, 0.104 and 0.057 μA μM−1 mm2 for Pb, Cu and Hg, respectively. The BD-NCD electrode also exhibits capability in simultaneous multi-metals determination although the presence of Cu ion was found to be a disturbance in the system as well. On the other hand, the high content of organics in the real water sample such as lake water also demonstrated to hinder heavy metals measurement. Thus, this study confirms that the BD-NCD after undergoing dynamic polarization are capable of direct determination of Pb, Cu and Hg ions both individually and simultaneously either in the acetate buffer solution or natural water system, within μM level.

Preparation of Boron-Doped Nanocrystalline Diamond Electrode and Its Wastewater Treatment Performance

Boron-doped nanocrystalline diamond (BDND) films were prepared on Ti substrate by hot filament chemical vapor deposition (HFCVD) method. The morphology, phases and quality of the BDND films were characterized by Scanning electron microscopy, X-Ray diffraction, and Raman spectroscopy. Cyclic voltammograms indicated that the BDND electrodes had wide electrochemical window, low background current and good electro-oxidation performance of phenol solution. The effects of operative parameters like current density and pH initial were investigated. The results show that both of the two variables have significant influence on the degradation performance of the organic pollutants. High COD removal can be achieved using high current density in acid solutions, and there exists optimal values of both parameters considering the current efficiency and operation economics.

Boron Doped Nanocrystalline Diamond Grown on Reticulated Vitreous Carbon: Morphological, Structural, and Electrochemical Characterizations

Reticulated vitreous carbon (RVC) is a macroporous material with high surface area, rigid structure, low resistance to fluid flow and high thermal and electrical conductivities. RVC has a wide range of applications as porous electrodes, high temperature insulation, filters, storage batteries, among others. Composites formed from diamond grown on sp2 bonded carbonaceous materials have already been studied, but there are still few publications about the electrochemical properties of this material. Then, the study of new hybrid nanomaterials is very important for understanding and promoting new technologies. In this work, boron-doped nanocrystalline diamond (BDND) films were deposited on RVC heat treated until 1000 °C and 1700 °C in order to evaluate the influence of different structural organization indexes of RVC on the nanocrystalline diamond grains formation as well as on their electrochemical performance. RVC was processed using poly(furfuryl) alcohol and polyurethane foams with 70 ppi (pores per inch) as mold. RVC substrates surfaces were prepared using seeding treatment in which samples are dipped in a 10 wt% solution of Poly diallyldimethylammonium chloride (PDDA) during 30 min followed by immersion in a nanodiamond (4nm) seeding dispersion for 10 min. The seeding step is necessary to improve diamond growth on carbon fiber in order to keep the surface carbon in sp3 configuration dominant over sp2 bond etching during diamond film growth. BDND films were grown on RVC heat treated until 1000 °C and 1700 °C using a hot-filament chemical vapor deposition (HFCVD) reactor. The boron doping was performed by dissolving B2O3 in methanol in a bubbler attached to the reactor. The solution was prepared with a concentration of B2O3 dissolved in CH3OH that correspond to B/C ratio of 30000 ppm. Hydrogen gas was used as a carrier with a constant flow of 30 sccm. The composites were evaluated by Scanning Electron Microscopy (SEM), Raman spectroscopy and cyclic voltammetry. Raman spectra and SEM images confirmed the BDND films achievement showing the RVC completely covered by a diamond coating. The electrochemical measurements were made by using Autolab PGSTAT 302 equipment with a three-electrode cell. The BDND/RVC composites obtained with different RVC heat treatment temperature (HTT), were used as working electrode. A platinum coil wire served as the counter electrode and Ag/AgCl was used as the reference electrode. The voltammetric curves (VC) were taken in H2SO4 0.5 mol.L-1 and showed a standard wide potential window as expected for BDND electrodes. In order to characterize the electrochemical kinetic we have applied CV using the redox couple of Fe(CN)6 3-/4- with different scan rates. This redox system includes reactions that depend on the specific interactions with the surface electrode. Besides, the electrode kinetics for this kind of redox couple tends to be more sensitive to the surface functionalities on sp2-bonded carbon electrodes. The BDND grown on RVC with higher HTT demonstrated the fast kinetics attributed to the better conductivity of such substrate.

Optimization of Actinides Trace Precipitation on Diamond/Si PIN Sensor for Alpha-Spectrometry in Aqueous Solution

We report here on a new approach for the detection and identification of actinides ( 239 Pu, 241 Am, 244 Cm, etc). This approach is based on the use of a novel device consisting of a boron doped nanocrystalline diamond film deposited onto a silicon PIN diode alpha particle sensor. The actinides concentration is probed in situ in the measuring solution using a method based on electro-precipitation that can be carried out via the use of a doped diamond electrode. The device allows probing directly both alpha-particles activity and energy in liquid solutions. In this work, we address the optimization of the actinides electro-precipitation step onto the sensor. The approach is based on fine tuning the pH of the electrolyte, the nature of the supporting electrolytes (Na 2 SO 4 or NaNO 3 ), the electrochemical cell geometry, the current density value, the precipitation duration as well as the sensor surface area. The deposition efficiency was significantly improved with values reaching for instance up to 81.5% in the case of electro-precipitation of 5.96 Bq 241 Am on the sensor. The diamond/silicon sensor can be reused after measurement by performing a fast decontamination step at high yields ≥99%, where the 241 Am electro-precipitated layer is quickly removed by applying an anodic current (+2 mA · cm -2 for 10 minutes) to the boron doped nanocrystalline diamond electrode in aqueous solution. This study demonstrated that alpha-particle spectroscopic measurements could be made feasible for the first time in aqueous solutions after an electrochemical deposition process, with theoretical detections thresholds as low as 0.24 Bq · L -1 . We believe that this approach can be of very high interest for alpha-particle spectroscopy in liquids for actinides trace detection.

Lead detection using micro/nanocrystalline boron-doped diamond by square-wave anodic stripping voltammetry

Monitoring heavy metal ion levels in water is essential for human health and safety. Electroanalytical techniques have presented important features to detect toxic trace heavy metals in the environment due to their high sensitivity associated with their easy operational procedures. Square-wave voltammetry is a powerful electrochemical technique that may be applied to both electrokinetic and analytical measurements, and the analysis of the characteristic parameters of this technique also enables the mechanism and kinetic evaluation of the electrochemical process under study. In this work, we present a complete optimized study on the heavy metal detection using diamond electrodes. It was analyzed the influence of the morphology characteristics as well as the doping level on micro/nanocrystalline boron-doped diamond films by means of square-wave anodic stripping voltammetry (SWASV) technique. The SWASV parameters were optimized for all films, considering that their kinetic response is dependent on the morphology and/or doping level. The films presented reversible results for the Lead [Pb (II)] system studied. The Pb (II) analysis was performed in ammonium acetate buffer at pH 4.5, varying the lead concentration in the range from 1 to 10μgL−1. The analytical responses were obtained for the four electrodes. However, the best low limit detection and reproducibility was found for boron doped nanocrystalline diamond electrodes (BDND) doped with 2000mgL−1 in B/C ratio.

Biocompatibility and electrochemical assessment of boron doped nanocrystalline diamond electrodes for neural stimulation

Event Abstract Back to Event Biocompatibility and electrochemical assessment of boron doped nanocrystalline diamond electrodes for neural stimulation Cristian P. Pennisi1*, Maria Alcaide1, Stavros Papaioannou1, Suzan Meijs2, Andy Taylor3, 4, Milos Nesladek5 and Vladimir Zachar1 1 Aalborg University, Dept. of Health Science and Technology, Denmark 2 Aalborg University, Dept. of Health Science and Technology, Denmark 3 ASCR, Institute of Physics, Czechia 4 NANO6, Czechia 5 University Hasselt, IMEC, Belgium Neural prostheses are devices that use electrical impulses to restore sensory or motor deficits following trauma or neurological diseases. In implanted devices, electrodes located in close proximity to the neural tissue are in charge of delivering the electrical impulses generated in a stimulation unit. The electrodes for neural stimulation possess one or various contact sites comprising a metal, such as platinum or iridium oxide, or a ceramic, such as titanium nitride (TiN). Although these are non-toxic materials with excellent electrochemical properties, many of the currently used designs display a compromised long-term performance as a result of the foreign body reaction. The growth of encapsulation tissue around the contact sites increases the distance between the electrode and neural cells over time. As a consequence, it is necessary to inject larger currents in order to achieve cell activation, which might exceed the potential at which oxidation and reduction of water takes place causing irreversible damage to the electrode and tissue. In recent years, nanocrystalline diamond (NCD) films have emerged as a unique class of biomaterials, which hold promise for the fabrication of neural electrodes due to their chemical inertness, biocompatibility and outstanding electrical properties (Pennisi and Alcaide, 2014). In this talk, a series of studies assessing the biocompatibility and electrochemical performance of boron doped NCD films for application in neural stimulation electrodes is described. The fabrication of boron doped NCD test substrates and electrodes by microwave chemical vapor deposition is presented. Furthermore, surface characterization of these substrates by Raman spectroscopy and atomic force microscopy is shown. Results of in vitro studies using the test substrates comprise protein adsorption, cytotoxicity, and cell proliferation and adhesion assays. These results are presented to describe the effects of the surface properties of the NCD films on the biological responses. We demonstrate that an increased surface roughness is crucial to significantly reduce adhesion and proliferation of fibroblasts on the NCD surfaces (Alcaide et al., 2014). The electrochemical performance and the in vivo biocompatibility of the boron doped NCD films are assessed using monopolar electrodes. It is shown that while electrical parameters such as impedance and charge injection capacity are similar to that of control TiN electrodes, NCD electrodes display a much wider water potential window, ranging from -1.7 to 1.4 V (Meijs et al.,2013). Data from the in vivo biocompatibility studies is also analyzed, consisting on the histological and histomorphometric assessment of the fibrous capsule after 2 and 4 weeks of subcutaneous implantation in a rat model. We show that implantation of NCD electrodes is associated with no signs of chronic inflammation and a very thin fibrous capsule, which after two weeks of implantation exhibit an average thickness of 25 μm. In summary, this talk presents data demonstrating that the proposed boron doped NCD electrodes can be safely operated within a wide potential window and cause a minimal foreign body reaction upon implantation. Taken together, these results indicate that boron doped NCD films represent a promising approach to mitigate the issues associated with fibrous encapsulation of neural stimulation electrodes Acknowledgements This work was supported by the EU through the project MERIDIAN (Micro and Nano Engineered Bi-Directional Carbon Interfaces for Advanced Peripheral Nervous System Prosthetics and Hybrid Bionics), contract n. 280778-02.

Boron‐Doped Nanocrystalline Diamond Microelectrode Arrays Monitor Cardiac Action Potentials

The expansion of diamond-based electronics in the area of biological interfacing has not been as thoroughly explored as applications in electrochemical sensing. However, the biocompatibility of diamond, large safe electrochemical window, stability, and tunable electronic properties provide opportunities to develop new devices for interfacing with electrogenic cells. Here, the fabrication of microelectrode arrays (MEAs) with boron-doped nanocrystalline diamond (BNCD) electrodes and their interfacing with cardiomyocyte-like HL-1 cells to detect cardiac action potentials are presented. A nonreductive means of structuring doped and undoped diamond on the same substrate is shown. The resulting BNCD electrodes show high stability under mechanical stress generated by the cells. It is shown that by fabricating the entire surface of the MEA with NCD, in patterns of conductive doped, and isolating undoped regions, signal detection may be improved up to four-fold over BNCD electrodes passivated with traditional isolators.

The Effect of pH on Electro-Oxidation of Phenolic Compounds at Boron-Doped Nanocrystalline Diamond Films (BDND)

The surface properties of boron-doped nanocrystalline diamond (BDND) films were investigated in regard to their electrochemical response to phenol, 4-chlorophenol and 4-nitrophenol. The films were produced using Hot Filament CVD technique on Si substrate with a gas mixture of CH4/H2/Ar. The morphology and quality of the BDND electrode were characterized by scanning electron microscopy and by Raman scattering spectroscopy. The BDND surface pre-treatment was carried out to evaluate the phenolic compounds detection efficiency induced by anodic polarization (AP) followed by cathodic polarization (CP) polarization in 1 mmol L−1 of these compounds in different pH range from 1 to 13.5. The use of cyclic and linear voltammetry with the BDND electrodes for the detection of these phenolics compounds is described.

Influence of the Doping Level at Boron Doped Nanocrystalline Diamond Films in the Electrochemical Determination of Nitrite

ABSTRACTIn this paper, the influence of the doping level at boron doped nanocrystalline diamond (BDND) films in the electrochemical determination of nitrite was reported. The morphology and the structure modifications as function of the boron doping level increase were observed. Two different doping levels were considered. A BDND film with a doping level of 30.000 ppm and one another with a doping level of 10.000 ppm was used. The columnar growth for the 30.000 ppm BDND led to a higher surface roughness and also to a greater grain size when compared to that 10.000 ppm BDND. The Raman spectra shown higher sp2-bonded carbon amount in grain boundary for the 10.000 ppm BDND film due to decrease of the grain size. The morphological and structural modifications of the BDND films were crucial for nitrite oxidation process. The 30.000 ppm BDND electrode presented a better sensitivity to the nitrite oxidation and a lower detection limit (DL) on the “as-grown” condition, while the 10.000 ppm BDND electrode presented a better analytical sensitivity and a lower DL after the surface pre-treatment with hydrogen plasma.

Fabrication of boron doped diamond microband electrodes for electrochemical detection in a microfluidic channel

The manufacturing and electrochemical characterisation of an array of 20 boron doped nanocrystalline diamond (BNCD) microband electrodes for use in a poly(dimethylsiloxane) (PDMS) based microfluidic system are described. The electrodes were fabricated by plasma etching of a silicon oxide- and BNCD thin film coated silicon wafer and the resulting surface structured silicon wafer was subsequently bonded to the PDMS so that the BNCD microband electrodes were located within the PDMS microchannel. The electrochemical performance of the BNCD electrodes was studied and the electrodes were found to exhibit significantly better stability than previously employed gold microband arrays.

Detection of phenol at boron-doped nanocrystalline diamond electrodes

The phenol quantification using boron-doped nanocrystalline diamond (BDND) from electroanalytical technique of square wave voltammetry (SWV) is reported. BDND depositions were performed using Hot Filament Chemical Vapor Deposition reactor, where it was possible to grow films with statics substrate-holder (sample S1) or with spinning substrate-holder (sample S2). The variation of this growth parameter induced significant changes on the electrode properties. For example, the electrode S2 presented smoothness surface with low roughness in relation to that for electrode S1. Besides, Raman spectra showed different features for both electrodes that could be related to boron incorporation. Electrochemical measurements also presented differences between electrodes, showing the advantages of electrode S2, such as, rapid charge transfer, large electrochemical area and excellent phenol detection limit ∼0.1mgL−1. The phenol standard sample of 8.0mgL−1 was used to validate the application of this electrode as a nanosensor. Its concentration calculated from SWV using electrode S2 was 8.2±0.2mgL−1 while from Ion Chromatograph it was 7.9±0.1mgL−1. These results demonstrated the high potential of BDND electrodes for electroanalytical applications.

Electrochemical studies of ganciclovir at boron-doped nanocrystalline diamond electrodes

The electrochemical oxidation of ganciclovir was investigated at boron-doped nanocrystalline diamond (BDND) electrodes by the use of cyclic voltammetry and differential pulse voltammetry. The optimization of the experimental variables including supporting electrolyte and pH value was studied, and the 0.04-M Britton–Robinson buffer solution (pH 2.5) was selected. The relationship of the oxidation peak potential to scan rate and pH value was also investigated, and 2 electron transfer and 2 proton participation for the oxidation process of ganciclovir at BDND electrode were obtained. Compared with boron-doped microcrystalline diamond and glassy carbon electrodes, the BDND electrode demonstrated the wider linear range of 0.5–350μM, lower limit of detection of 0.2μM, and higher reproducibility and stability for the determination of ganciclovir under the optimum conditions. For the analysis of ganciclovir in human serum at the BDND electrodes, precision and accuracy were checked by recovery experiments.

A novel tyrosinase biosensor based on biofunctional ZnO nanorod microarrays on the nanocrystalline diamond electrode for detection of phenolic compounds

A novel tyrosinase biosensor based on biofuncational ZnO nanorod microarrays on the boron-doped nanocrystalline diamond (BDND) substrates was developed. The ZnO nanorod microarrays were firstly deposited on BDND thin film surfaces via a low-temperature solution method, and then ZnO nanorods were functionalized with the mixture of 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS) by a co-condensation approach, then tyrosinase was immobilized to amino-modification ZnO nanorod surfaces by the covalent binding. As-prepared tyrosinase biosensors were used for the detection of phenolic compounds. The tyrosinase-modified BDND electrode gave a linear response range of 1–175, 1–150 and 1–150 µM and sensitivity of 576.2, 339.3 and 287.1 µA mmol − 1 cm − 2 for p-cresol, 4-chlorophenol and phenol, respectively. The low detection limit was estimated to be 0.1, 0.25 and 0.2 µM ( s b/ m = 3), respectively. Therefore, the biofunctional ZnO nanorod arrays have potential applications as platforms to immobilize other enzymes and bioactive molecules in biosensors.