Boron-doped Ultrananocrystalline Diamond Research Articles

Novel approach to produce 3D boron-doped diamond for pollutant removal from water

Diamond growth from Chemical Vapor Deposition (CVD) on foreign substrates can require different pretreatment not only to improve the film nucleation but also to assure its adhesion by decreasing the expected film/substrate interface stress. To improve boron-doped film nucleation, growth, and adherence, different substrate pretreatments have been used mainly from the seeding process with diamond powder at various particle sizes. Despite this, the development of diamond growth on a Ti mesh remains difficult because of the requirement of a cohesive film to cover a 3D macroporous sample with varying growth rates based on its distinct network geometry. Then, this work describes a novel approach to growing boron-doped diamond (BDD) and boron-doped ultrananocrystalline diamond (B-UNCD) on titanium dioxide nanotubes (TDNT) produced simultaneously on both sides of Ti mesh by an anodization process. The films were obtained from two-step growth processes by assuring the entire diamond overlay on both TDNT/Ti mesh sides, including their outer/inner surfaces, as a 3D sample. TiO2 - TiC conversion has dominated the renucleation process, facilitating the nanometric scale control. The film morphologies were systematically analyzed by FEG-SEM images at different sample planes and depths for both sample sides at different stages of film growth. The unique morphology of titania nanotubes associated with columnar and/or renucleation development of BDD, considering the film defects and valley, can systematically increase the electrode specific area. Raman spectra showed the film quality and its micro and/or ultrananodiamond structure and the boron doping features. Also, this growth process allowed a dopant-controlled adjustable conductivity. Then, the boron doping levels for both films were evaluated from Mott-Schottky plots at around 1019 Bcm−3, characterizing them with good conductivity. In addition, electrochemical measurements from Cyclic Voltammetry (CV) confirmed the expected diamond response on redox pair following the quasi-reversible criteria as high-performance diamond electrodes and in situ Raman spectroelectrochemical measurements assessed the stability of samples during electrochemical measurements, ensuring structural integrity. Finally, the samples were applied to the degradation of methylene blue, proving to be superior materials for electrochemical applications due to their advantages compared to those of similar 2D electrodes.

Electrochemical determination of ibuprofen by batch‐injection analysis using a BORON‐doped ultrananocrystalline diamond electrode

AbstractIn this paper, the evaluation of a boron‐doped ultrananocrystalline diamond (BD‐UNCD) electrode for the determination of ibuprofen (IBU) in pharmaceutical formulations using batch‐injection analysis with amperometric detection (BIA‐AD) is presented. The BD‐UNCD electrode was characterized by Raman spectroscopy and the electrochemical measurements were carried out before and after anodic pretreatment. An improved electrochemical response for IBU oxidation was observed using BD‐UNCD as compared to commercial boron‐doped diamond electrode. The optimized method based on the BIA‐AD system was carried out by using 2.0 V as the detection potential, a dispensing rate of 211.9 μL s−1, and an injection volume of 40 μL in an electrochemical cell containing 30.0 mL of 1.0 mol L−1 HClO4 as the supporting electrolyte. The proposed method provided an analytical curve within a linear dynamic range from 1.84 to 20.0 μmol L−1 (R2=0.9967) and a limit of detection of 0.55 μmol L−1. The intra‐day (n=10) and inter‐day (n=2) precisions for IBU concentrations of 5.0 and 10.0 μmol L−1 assessed as relative standard deviation (%RSD) ranged from 2.65 to 5.84 %. The accuracy of the method was assessed through the determination of IBU in pharmaceutical samples (tablets and solutions), yielding results that were consistent with those obtained through the comparative method (HPLC‐DAD).

Highly porous seeding-free boron-doped ultrananocrystalline diamond used as high-performance anode for electrochemical removal of carbaryl from water

Boron-doped diamond (BDD) electrodes are regarded as the most promising catalytic materials that are highly efficient and suitable for application in advanced electrochemical oxidation processes targeted at the removal of recalcitrant contaminants in different water matrices. Improving the synthesis of these electrodes through the enhancement of their morphology, structure and stability has become the goal of the material scientists. The present work reports the use of an ultranano-diamond electrode with a highly porous structure (B-UNCDWS/TDNT/Ti) for the treatment of water containing carbaryl. The application of the proposed electrode at current density of 75 mA cm−2 led to the complete removal of the pollutant (carbaryl) from the synthetic medium in 30 min of electrolysis with an electric energy per order of 4.01 kWh m−3 order−1. The results obtained from the time-course analysis of the carboxylic acids and nitrogen-based ions present in the solution showed that the concentrations of nitrogen-based ions were within the established maximum levels for human consumption. Under optimal operating conditions, the proposed electrode was successfully employed for the complete removal of carbaryl in real water. Thus, the findings of this study show that the unique, easy-to-prepare BDD-based electrode proposed in this study is a highly efficient tool which has excellent application potential for the removal of recalcitrant pollutants in water.

Achievement and electrochemical responsiveness of advanced boron-doped ultrananocrystalline diamond on highly ordered titanium dioxide nanotubes

Boron-doped ultrananocrystalline diamond grown on titanium dioxide nanotubes without seeding pre-treatment (B-UNCDWS/TDNT/Ti), as a porous composite, was successfully achieved. Innovative approaches concerning the highly ordered TDNT production as well as its singular diamond formation by hot filament chemical vapor deposition (CVD) were explored. The B-UNCD homogeneous cluster progress on the TDNT porous walls as a function of the growth times from 1 to 7 h led to remarkable composite morphologies, keeping the TDNT porosity, where the TiO2 – TiC conversion dominated the renucleation process facilitating the nanometric scale control. Scanning electron microscopy images confirmed the continuous ultrananocrystalline formation as nanoclusters on the TDNT walls with their size evolution as a function of growth time also showing an increase in the CVD diamond ballas clusters. Raman spectra and X-Ray patterns exhibited the diamond characteristics with defined peaks and TiC formation, as expected. The ID(220)/(111) and ID(311)/(111) ratio intensities pointed out the films governed by (220) diamond phase, due to their high renucleation process. Besides, the intensity ratios for both TiC (111) and TiC (200) phases with D(111) peak showed a carbon atoms competition between surface and bulk diffusion on the TiC layer. The electrode reversibility evaluated from cyclic voltammetry curves followed the quasi-reversible criteria for all samples, confirming their promising performance. Mott-Shottky plots are in good agreement with Raman spectra for boron-doped films from 1018 to 1019 B.cm−3 where the highest doped diamond was obtained for the thickest films of 5 and 7 h.

Performance testing of mesh anodes for in situ electrochemical oxidation of PFAS

Groundwater remediation technologies that can destroy per- and polyfluoroalkyl substances (PFAS) in situ are in high demand. To address this need, using flow-through electrochemical reactors we compared the performance of three mesh electrode materials that may be implemented in the subsurface as permeable reactive barriers. A Magnéli-phase titanium suboxides TinO2n-1 anode achieved higher perfluorooctane sulfonate (PFOS) oxidation rates and lower energy consumption than boron-doped ultrananocrystalline diamond and IrO2-Ta2O5 mixed metal oxides, and was thus selected for more detailed testing regarding the impacts of varying current density, flow velocity, electrolyte conductivity, and PFOS concentration. Over 99% of PFOS removal was achieved under continuous flow conditions. The fluorine mass balance showed that most PFOS-bonded F was released as fluoride, while no organic intermediates were detected in the aqueous phase. Each ∼2% of fluorine was recovered as HF and organofluorine intermediates in the gas phase. A comparison of 10 PFAS revealed a hydrophobicity-driven increase in oxidation rate with increasing perfluoroalkyl chain length as well as faster oxidation kinetics for perfluoroalkyl carboxylic acids compared to perfluoroalkane sulfonic acids, likely due to contributions from electrochemically activated sulfate. The energy consumption of PFAS treatment under simulated slow-flow groundwater conditions was substantially higher than in ex situ electrochemical systems optimized for enhanced mass transfer. Consequently, future work should focus on in situ treatment design optimization with an emphasis on power requirements. Collectively, our investigations demonstrate that among the few water treatment technologies capable of breaking the carbon-fluorine bond, electrochemical treatment is a promising approach for in situ destruction of PFAS in the subsurface.

Nafion and Multiwall Carbon Nanotube Modified Ultrananocrystalline Diamond Microelectrodes for Detection of Dopamine and Serotonin.

Neurochemicals play a critical role in the function of the human brain in healthy and diseased states. Here, we have investigated three types of microelectrodes, namely boron-doped ultrananocrystalline diamond (BDUNCD), nafion-modified BDUNCD, and nafion–multi-walled carbon nanotube (MWCNT)-modified BDUNCD microelectrodes for long-term neurochemical detection. A ~50 nm-thick nafion–200-nm-thick MWCNT-modified BDUNCD microelectrode provided an excellent combination of sensitivity and selectivity for the detection of dopamine (DA; 6.75 μA μM−1 cm−2) and serotonin (5-HT; 4.55 μA μM−1 cm−2) in the presence of excess amounts of ascorbic acid (AA), the most common interferent. Surface stability studies employing droplet-based microfluidics demonstrate rapid response time (<2 s) and low limits of detection (5.4 ± 0.40 nM). Furthermore, we observed distinguishable DA and 5-HT current peaks in a ternary mixture during long-term stability studies (up to 9 h) with nafion–MWCNT-modified BDUNCD microelectrodes. Reduced fouling on the modified BDUNCD microelectrode surface offers significant advantages for their use in long-term neurochemical detection as compared to those of prior-art microelectrodes.

Precise ultrananocrystalline diamond nanowire arrays for high performance gas sensing application

We report that the boron-doped Ultrananocrystalline diamond (UNCD) nanowires with extremely high length to diameter ratio and oxygen functional groups possess an intrinsic nature capable of adsorbing carbon monoxide (CO) molecules. The purpose is to develop high performance of UNCD nanowire arrays gas sensor. Highly flat UNCD thin film with thickness of 70 nm was firstly grown on Si substrate. The film main consists of a large amount of UNCD grain with size smaller than 10 nm. Successive processes were performed afterward to fabricate three groups of UNCD nanowire arrays. Then the sensing performances of the fabricated devices with different structures including serial connection and parallel connection of the nanowires were evaluated. Furthermore, corresponding kinetic model and sensing mechanism have also been discussed. Small grain size, high length to diameter ratio and the existence of oxygen functional groups have been ascribed as the key factors for promoting CO gas adsorption that largely enhances device gas sensing performances.

Lab‐on‐a‐Chip for hydrogen sulphide detection—Part II: Integrated with screen‐printed electrode

AbstractThe measurement of hydrogen sulphide (H2S) has held the attention of the analytical community due to its unique physiological and pathophysiological roles in biological systems. This work reports fabrication and characterization of screen‐printed electrode (SPE) integrated lab‐on‐a‐chip (LOAC) for H2S detection. The device has been designed to detect all forms of H2S present in the plasma; however, current work is a proof of concept of device operation for free sulphide. The device consists of three distinct layers for H2S separation and SPE to detect H2S. It operates with pH‐dependent liberation and trapping from samples introduced. The first layer, the releasing layer, consists of a releasing chamber for the liberation of H2S. The second layer, a silicone membrane, is where gas diffuses from the sample layer to the third layer. The third layer, the trapping layer, is integrated with SPE to determine the concentration of H2S. The device uses an electrochemical technique. First, electrode performances are tested on the cell vial to establish suitability for subsequent LOAC incorporation. Common metal electrodes are compared with boron‐doped ultra‐nano‐crystalline diamond (BDUNCD) electrode and SPE. The range of detection, detection limit, and sensitivity of the electrode are characterized. In conclusion, a proof of concept of an electrochemical sensing of H2S in a LOAC is reported. The device is portable, robust and can easily be fabricated. Transfer data indicated that 10% sulphide detected into the trapping chamber in a reproducible manner at 20 min. The SPE integrated LOAC shows a huge advantage over conventional techniques.

Nanoplasmonic 1D Diamond UV Photodetectors with High Performance

Diamond nanowires have recently drawn substantial attention because of their unique physical and chemical properties for electrochemical sensors, optoelectronics, and nanophotonics applications. However, diamond nanowire-based ultraviolet photodetectors have not been reported because of the challenges involved in synthesizing crystalline diamond nanowires with controllable morphologies and, more fundamentally, the material's high carrier concentration with low mobilities that limits the obtainable photoresponsivity. The synergetic integration of ultrananocrystalline diamond (UNCD) nanowires with nanoplasmonic enhancement by noble metal nanoparticles is a very promising approach to overcome these shortcomings. Here we report the fabrication of boron-doped ultrananocrystalline diamond nanowires functionalized with the platinum nanoparticles to form self-powered ultraviolet photodetectors that exhibit an ultrahigh photoresponsivity of 388 Amp/Watt at 300 nm wavelength, a fast response time around 20 ms, and a good UV/visible rejection ratio of about 5 orders of magnitude under zero-bias condition.

Advancing Electrochemical Microsensor Technologies Using Carbon Nanomaterials for Chronic Dopamine Detection

Analytical microsensors that can reliably detect (bio)molecules in real-time long-term represent one of the greatest challenges for health and environmental monitoring. Developing such microsensors with high sensitivity and selectivity in minimally prepared complex samples is especially difficult. In recent years, the application of nanomaterials and advanced fabrication methods to microsensing has demonstrated major enhancements in key microsensor performance metrics and their ease of integration into miniaturized microelectrode microarray sensor platforms. In this work, we report the electrochemical response of a boron-doped ultrananocrystalline diamond (BDUNCD) microelectrode during long-term dopamine (DA) detection. Specifically, changes to its electrochemical activity and electroactive area due to DA-by products and surface oxidation are studied via scanning electron microscopy, energy dispersive spectroscopy, electrochemical impedance spectroscopy and silver deposition imaging (SDI). The fouling studies with amperometry (AM) and fast scan cyclic voltammetry (FSCV) methods suggest that the microelectrodes are heavily fouled due to poor DA-dopamine-o-quinone cyclization rates followed by a combination of polymer formation and major changes in their surface chemistry. SDI data confirms the presence of the insulating polymer with sparsely-distributed tiny electroactive regions. This resulted in severely distorted DA signals and a 90% loss in signal starting as early as 3 hrs for AM and a 56% loss at 6.5 hrs for FSCV. This underscores the need for cleaning of the fouled microelectrodes if they have to be used long-term. Out of the three in vivo suitable electrochemical cycling cleaning waveforms investigated, the standard waveform (-0.4 V to +1.0 V) provides the best cleaned surface with a fully retained voltammogram shape, no hysteresis, no DA signal loss (a 90±0.72 nA increase) and the smallest charge transfer resistance value of 0.4±0.02 MW even after 6.5 hrs of monitoring. Most importantly, this is the same waveform that is widely used for in vivo detection with carbon fiber microelectrodes. Future work to test these microelectrodes for more than 24 hrs of DA detection is anticipated.

Surface Fouling of Ultrananocrystalline Diamond Microelectrodes during Dopamine Detection: Improving Lifetime via Electrochemical Cycling.

In this work, we report the electrochemical response of a boron-doped ultrananocrystalline diamond (BDUNCD) microelectrode during long-term dopamine (DA) detection. Specifically, changes to its electrochemical activity and electroactive area due to DA byproducts and surface oxidation are studied via scanning electron microscopy, energy dispersive spectroscopy, electrochemical impedance spectroscopy, and silver deposition imaging (SDI). The fouling studies with amperometry (AM) and fast scan cyclic voltammetry (FSCV) methods suggest that the microelectrodes are heavily fouled due to poor DA-dopamine- o-quinone cyclization rates followed by a combination of polymer formation and major changes in their surface chemistry. SDI data confirms the presence of the insulating polymer with sparsely distributed tiny electroactive regions. This resulted in severely distorted DA signals and a 90% loss in signal starting as early as 3 h for AM and a 56% loss at 6.5 h for FSCV. This underscores the need for cleaning of the fouled microelectrodes if they have to be used long-term. Out of the three in vivo suitable electrochemical cycling cleaning waveforms investigated, the standard waveform (-0.4 V to +1.0 V) provides the best cleaned surface with a fully retained voltammogram shape, no hysteresis, no DA signal loss (a 90 ± 0.72 nA increase), and the smallest charge transfer resistance value of 0.4 ± 0.02 MΩ even after 6.5 h of monitoring. Most importantly, this is the same waveform that is widely used for in vivo detection with carbon fiber microelectrodes. Future work to test these microelectrodes for more than 24 h of DA detection is anticipated.

Influence of modified carbon substrate on boron doped ultrananocrystalline diamond deposition

Boron doped ultrananocrystalline diamond (B-UNCD) growth was studied on modified reticulated vitreous carbon (RVC) produced from poly(furfuryl alcohol) (PFA) resin with sodium hydroxide additions at two different heat treatment temperatures. The different amounts of NaOH in PFA (up to reaching pH values of around 3, 5, 7, and 9) aimed to neutralize the acid catalyst and to increase the PFA storage life. Besides, this procedure was responsible for increasing the oxygen content of RVC samples. Thus, the effect of carbon and oxygen coming from the substrates in addition to their different graphitization indexes on diamond morphology, grain size, preferential growth and boron doping level were investigated by FEG-SEM, x-ray diffraction and Raman spectroscopy. Therefore, B-UNCD films were successfully grown on RVC with pH values of 3, 5, 7, and 9 heat treated at 1000 and 1700 °C. Nonetheless, the higher oxygen amount during B-UNCD growth for samples with pH 7 and 9 heat treated at 1000 °C was responsible for the RVC surface etching and the decrease in the boron concentration of such samples. The cross section images showed that B-UNCD infiltrated at around 0.9 mm in depth of RVC samples while carbon nanowalls were observed mainly on RVC samples heat treated at 1000 °C for all pH range studied.

Detection of neurochemicals with enhanced sensitivity and selectivity via hybrid multiwall carbon nanotube-ultrananocrystalline diamond microelectrodes.

Abnormal neurochemical signaling is often the underlying cause of brain disorders. Electrochemical microsensors are widely used to monitor neurochemicals with high spatial-temporal resolution. However, they rely on carbon fiber microelectrodes that often limit their sensing performance. In this study, we demonstrate the potential of a hybrid multiwall carbon nanotube (MWCNT) film modified boron-doped ultrananocrystalline diamond (UNCD) microelectrode (250 μm diameter) microsensor for improved detection of dopamine (DA) in the presence of common interferents. A series of modified microelectrodes with varying film thicknesses were microfabricated by electrophoretic deposition (EPD) and characterized by scanning electron microscopy, x-ray photoelectron spectroscopy, electrochemical impedance spectroscopy (EIS) and silver deposition imaging. Using cyclic voltammetry, the 100-nm "thin" film microelectrode produced the most favorable combination of DA sensitivity value of 36 ±2% μA/μM/cm2 with a linear range of 33 nM to 1 μM and a limit of detection (LOD) of 9.5 ± 1.2% nM. The EIS spectra of these microelectrodes revealed three regions with inhomogeneous pore geometry and differing impedance values and electrochemical activity, which was found to be film thickness dependent. Using differential pulse voltammetry, the modified microelectrode showed excellent selectivity by exhibiting three distinct peaks for the DA, serotonin and excess ascorbic acid in a ternary mixture. These results provide two key benefits: first, remarkable improvements in DA sensitivity (>125-fold), selectivity (>2000-fold) and LOD (>180-fold), second, these MWCNTs can be selectively coated with a simple, scalable and low cost EPD process for highly multiplexed microsensor technologies. These advances offer considerable promise for further progress in chemical neurosciences.

Enhanced H2O2 Production at Reductive Potentials from Oxidized Boron-Doped Ultrananocrystalline Diamond Electrodes.

This work investigates the surface chemistry of H2O2 generation on a boron-doped ultrananocrystalline diamond (BD-UNCD) electrode. It is motivated by the need to efficiently disinfect liquid waste in resource constrained environments with limited electrical power. X-ray photoelectron spectroscopy was used to identify functional groups on the BD-UNCD electrode surfaces while the electrochemical potentials of generation for these functional groups were determined via cyclic voltammetry, chronocoulometry, and chronoamperometry. A colorimetric technique was employed to determine the concentration and current efficiency of H2O2 produced at different potentials. Results showed that preanodization of an as-grown BD-UNCD electrode can enhance the production of H2O2 in a strong acidic environment (pH 0.5) at reductive potentials. It is proposed that the electrogeneration of functional groups at oxidative potentials during preanodization allows for an increased current density during the successive electrolysis at reductive potentials that correlates to an enhanced production of H2O2. Through potential cycling methods, and by optimizing the applied potentials and duty cycle, the functional groups can be stabilized allowing continuous production of H2O2 more efficiently compared to static potential methods.

Boron-Doped Ultrananocrystalline Diamond Microelectrodes for Chronic Dopamine Monitoring

Understanding the role of neurochemicals in human brain function is challenging. Researchers have showed the importance of extracellular neurotransmitters (NTs) such as dopamine, glutamate, GABA, adenosine and serotonin in Epilepsy, Schizophrenia and Parkinson’s disease. Among these NTs, dopamine (DA) has significant impact on motor and cognitive functions. New age miniaturized prosthetic devices coupled with modern sensing and stimulation electrodes provide a unique opportunity to apply fast scan cyclic voltammetry (FSCV) for chronic DA monitoring with millisecond resolution in vivo. In addition to traditional carbon electrode materials such as glassy carbon and pyrolytic graphite, emerging carbon nanomaterials such as nanotubes, nanofibers and nanodiamonds have spurred immense interest due to their high signal sensitivity and adequate resistance to surface fouling in implant environments. Among carbon electrode materials, boron-doped diamond (BDD) has unique properties such as high thermal conductivity, chemical inertness, biocompatibility, high mechanical stability, and high corrosion and fouling resistance, which makes it an excellent electrode material. In this work, boron-doped ultrananocrystalline diamond (BDUNCD) with 3-5 nm diamond crystallites with wide electrochemical potential window, flexible surface chemistry, low capacitive background current and ultra-smooth conformal surface with minimal non-specific adsorption to biomolecules is used for chronic DA sensing in vitro. The current gold standard electrode for DA sensing is carbon fiber microelectrode (CFM) with ~5 – 10 μm diameters. But CFMs are susceptible to surface fouling and are limited mostly to acute studies (<4h). In this talk, we discuss the dimensional stability of BDUNCD microelectrodes during DA monitoring for ~8 million electrochemical cycles in PBS buffer solution. We developed a new protocol to study BDUNCD electrode fouling and conductive and nonconductive regions by depositing silver nanoparticles and mapping their growth and distribution. Custom-made microfluidics is used to precisely control the microenvironment around the BDUCND microelectrode array. The fouling rates in 100 µM DA solution is systematically studied at different electrochemical potential windows (-0.6 V to 1.2 V) at 60 Hz for up to 7 h. During high frequency FSCV cycling with high current density, severe oxidative fouling and passivation is observed. This results in ~56% fouling at ~1.4 million cycles, i.e. an overall monitoring time of 7 h. Finally, the effect of in situ electrochemical cleaning will be discussed.

Wastewater Disinfection Using Potential Switching Methods on Boron Doped Ultrananocrystalline Diamond Electrodes

Boron-doped diamond (BDD) has attracted considerable attention as an electrode material used for electrochemical disinfection of wastewater, due to its high oxygen evolution over-potential.[1], [2] This property enables the formation of highly reactive oxygen species (ROS) such as hydroxyl radicals, ozone, and hydrogen peroxide.[3]–[6] Despite the promise of BDD as a liquid disinfection electrode, there is little information in literature that details the optimal conditions for ROS generation. Effects of potential switching for inhibiting fouling of the electrode surface, evolving surface chemistry, and resultant energy efficiency in sanitizing wastewater are not widely reported. Knowledge of these conditions and their liquid disinfection properties would allow production of ROS with higher efficiency and therefore lower cost in real-world applications. The present work investigates the generation of ROS and subsequent liquid disinfection of wastewater using as-grown boron-doped ultrananocrystalline diamond (BD-UNCD) electrodes. Static and potential switching methods of generating ROS are compared to determine their effects on liquid disinfection, chlorine generation, energy expenditure, electrode fouling, and electrode surface chemistry. These results build on an evolving understanding of the electrochemical generation of ROS from BDD electrodes. Our results show that liquid disinfection of diluted wastewater can occur with negligible chlorination and efficient energy expenditure using potential switching methods. Comparison of potential switching to static potential methods show differences in energy expenditure, chlorination, and electrode scaling; as well as time needed for disinfection of liquid waste. It is proposed that the electrogeneration of functional groups at oxidative potentials of BD-UNCD allows for an increased current density during the successive electrolysis at reductive potentials, and that this electrogeneration correlates to an enhanced production of H2O2. Through potential switching, these functional groups can be stabilized and used continuously to more efficiently produce H2O2, and potentially other ROS, when compared to static potential methods at these same potentials by optimizing the applied potentials and duty cycle. Moreover, potential switching has been previously used to inhibit electrode fouling,[7]–[10] which is commonplace in liquid waste sanitation, and therefore offers a practical method for electrochemical disinfection of wastewater in large scale applications.

Boron-doped diamond nanowires for CO gas sensing application

Three groups of boron-doped ultrananocrystalline diamond (B-UNCD) nanowires (NWs) arrayed on a silicon substrate were prepared by the successive processes: microwave plasma chemical vapor deposition, electron-beam lithography and reactive ion etching. Au electrodes built on both ends of each group of B-UNCD NWs were combined with a basic electrical circuit to form high-performance gas sensor arrays for carbon monoxide (CO) sensing measurements. the B-UNCD with boundary grain size around few nanometers of has been successfully synthesized, and three groups of reasonable straight diamond NWs with the same diameter and different lengths were built on one single substrate. The heavily boron doping of boron ions in the UNCD induced the ohmic contact between diamond and Au electrodes.

Enabling long term monitoring of dopamine using dimensionally stable ultrananocrystalline diamond microelectrodes

Chronic dopamine (DA) monitoring is a critical enabling technology to identify the neural basis of human behavior. Carbon fiber microelectrodes (CFM), the current gold standard electrode for in vivo fast scan cyclic voltammetry (FSCV), rapidly loses sensitivity due to surface fouling during chronic neural testing. Periodic voltage excursions at elevated anodic potentials regenerate fouled CFM surfaces but they also chemically degrade the CFM surfaces. Here, we compare the dimensional stability of 150 μm boron-doped ultrananocrystalline diamond (BDUNCD) microelectrodes in 1X PBS during ‘electrochemical cleaning’ with a similar-sized CFM. Scanning electron microscopy and Raman spectroscopy confirm the exceptional dimensional stability of BDUNCD after 40 h of FSCV cycling (∼8 million cycles). The fitting of electrochemical impedance spectroscopy data to an appropriate circuit model shows a 2x increase in charge transfer resistance and an additional RC element, which suggests oxidation of BDUNCD electrode surface. This could have likely increased the DA oxidation potential by ∼34% to +308 mV. A 2x increase in BDUNCD grain capacitance and a negligible change in grain boundary impedance suggests regeneration of grains and the exposure of new grain boundaries, respectively. Overall, DA voltammogram signals were reduced by only ∼20%. In contrast, the CFM is completely etched with a ∼90% reduction in the DA signal using the same cleaning conditions. Thus, BDUNCD provides a robust electrode surface that is amenable to repeated and aggressive cleaning which could be used for chronic DA sensing.

Toward a Boron-Doped Ultrananocrystalline Diamond Electrode-Based Dielectrophoretic Preconcentrator.

This paper presents results on immunobeads-based isolation of rare bacteria and their capture at a boron-doped ultrananocrystalline diamond (BD-UNCD) electrode in a microfluidic dielectrophoretic preconcentrator. We systematically vary the bead surface chemistry and the BD-UNCD surface chemistry and apply dielectrophoresis to improve the specific and the nonspecific capture of bacteria or beads. Immunobeads were synthesized by conjugating antibodies to epoxy-/sulfate, aldehyde-/sulfate, or carboxylate-modified beads with or without poly(ethylene glycol) (PEG) coimmobilization. The carboxylate-modified beads with PEG provided the highest capture efficiency (∼65%) and selectivity (∼95%) in isolating live Escherichia coli O157:H7 from cultures containing 1000 E. coli O157:H7 colony-forming units (cfu)/mL, or ∼500 E. coli O157:H7 and ∼500 E. coli K12 cfu/mL. Higher specificity was achieved with the addition of PEG to the antibody-functionalized bead surface, highest with epoxy-/sulfate beads (85-86%), followed by carboxylate-modified beads (76-78%) and aldehyde-/sulfate beads (74-76%). The bare BD-UNCD electrodes of the preconcentrator successfully withstood 240 kV/m for 100 min that was required for the microfluidic dielectrophoresis of 1 mL of sample. As expected, the application of dielectrophoresis increased the specific and the nonspecific capture of immunobeads at the BD-UNCD electrodes; however, the capture specificity remained unaltered. The addition of PEG to the antibody-functionalized BD-UNCD surface had little effect on the specificity in immunobeads capture. These results warrant the fabrication of electrical biosensors with BD-UNCD so that dielectrophoretic preconcentration can be performed directly at the biosensing electrodes.

同軸型アークプラズマ蒸着法により作製したホウ素添加超ナノ微結晶ダイヤモンド/アモルファス炭素混相膜の電気化学特性

Boron-doped ultrananocrystalline diamond (UNCD) amorphous carbon (a-C) composite films were fabricated by a coaxial arc plasma deposition (CAPD) method. Cyclic voltammetry measurements of deposited films showed wide electrical potential window and very low background current, which remarkably similar to conductive poly crystalline diamond (PCD) electrodes. In addition, it was confirmed that deposited films have removal effects of total organic carbon (TOC) in an ethanol water solution. Boron-doped UNCD/a-C films have potential for behaving as an electrode with wastewater treatment effects.