Reticulated Vitreous Carbon Electrode Research Articles

Enhanced electrochemical activity of boron-doped nanocarbon functionalized reticulated vitreous carbon structures for water treatment applications

An extraordinary charge transfer kinetics and chemical stability make a boron-doped diamond (BDD) a promising material for electrochemical applications including wastewater treatment. Yet, with flat geometrical surfaces its scaling options are limited. In this study, the reticulated Vitreous Carbon (RVC) served as a substrate for boron-doped diamondized nanocarbons (BDNC) film growth resulting with complex heterogeneity carbon structures with different morphologies defined by using electron microscopy, microtomography, activation energy studies, and Raman spectroscopy.The proposed modification significantly boosted the electrochemical Fe(CN)63−/4− redox activity. The voltammetry and impedimetric studies revealed its origin as a significantly higher share of electrochemically active sites at the BDNC@RVC electrode (increased by 114 %) combined with enhanced heterogeneous rate constant (2× increase up to 8.24·10−4 cm s−1). Finally, to establish its applicability for water treatment, the BDNC@RVC was studied as the anode in electrochemical paracetamol decomposition. Boron-enriched nanoarchitecture formed at the RVC electrode surface substantially reduced the oxidation energy barrier manifested as a decrease in activation overpotential by 212 mV, which gave a consequence in a 78 % removal rate (in 4 h, at 0.7 mA cm−2), 12 % higher than bare RVC and yielding lower amounts of APAP decomposition intermediates.

Electrochemical Characteristics of Shewanella loihica PV-4 on Reticulated Vitreous Carbon (RVC) with Different Potentials Applied.

The current output of an anodic bioelectrochemical system (BES) depends upon the extracellular electron transfer (EET) rate from electricigens to the electrodes. Thus, investigation of EET mechanisms between electricigens and solid electrodes is essential. Here, reticulated vitreous carbon (RVC) electrodes are used to increase the surface available for biofilm formation of the known electricigen Shewanella loihica PV-4, which is limited in conventional flat electrodes. S. loihica PV-4 utilizes flavin-mediated EET at potential lower than the outer membrane cytochromes (OMC), while at higher potential, both direct electron transfer (DET) and mediated electron transfer (MET) contribute to the current output. Results show that high electrode potential favors cell attachment on RVC, which enhances the current output. DET is the prevailing mechanism in early biofilm, while the contribution of MET to current output increased as the biofilm matured. Electrochemical analysis under starvation shows that the mediators could be confined in the biofilm. The morphology of biofilm shows bacteria distributed on the top layer of honeycomb structures, preferentially on the flat areas. This study provides insights into the EET pathways of S. loihica PV-4 on porous RVC electrodes at different biofilm ages and different set potential, which is important for the design of real-world BES.

The soluble lead flow battery: Image-based modelling of porous carbon electrodes

A novel numerical modelling framework coupling physics-based model equations and image-based input parameters is developed to simulate the behaviour of the soluble lead flow battery when reticulated vitreous carbon (RVC) electrodes are used. Experimental results are presented to validate the model. Open-source software OpenImpala is used to predict the macro-homogeneous properties of RVC from computed tomography scans of various grades of RVC. The process is repeated on manipulated datasets where a voxel dilation technique has been used to estimate the geometry of RVC electrodes with a range of thicknesses of electrodeposited material. The model predicts that with a region of free electrolyte dividing the electrodes, the electrolyte velocity is low within the electrodes. This is exacerbated by a build-up of deposit close to the inlet. By dividing the electrodes with only a porous separator, a deposit build-up is no longer seen, and the concentration within the electrodes is shown to be far more even. Finally, with an applied current density of 50 mA cm−2, the overpotential is predicted to be reduced by over 100 mV when 100 ppi RVC electrodes are used instead of 10 ppi electrodes. An experimentally validated voltage efficiency of over 80% is achieved.

Recent advances on modified reticulated vitreous carbon for water and wastewater treatment – A mini-review

Recently, modifications on reticulated vitreous carbon (RVC) have attracted attention as a promising strategy to produce low-cost, stable, and highly active electrodes leading to significant advances in the water/wastewater treatment field compared with raw RVC. Modified RVC materials have been used as cathode, anode, and membrane. Improvements on physical and electrocatalytic properties are achieved by RVC modification via diverse strategies, including the deposition of metal oxides, the introduction of surface functional groups, and the formation of composites, which were used to remove organic contaminants and pathogens from water matrices, as summarized in this mini-review. This mini-review mainly focused on papers published from 2015 to 2020 that reported modified RVC electrodes to eliminate pollutants and pathogens from water matrices by electrochemical advanced oxidation processes. Likewise, news challenges and opportunities are discussed, and perspectives for the ongoing and future studies in this research field are also given.

Growth of cobalt hexacyanoferrate particles through electrodeposition and chemical etching of cobalt precursors on reticulated vitreous carbon foams for Na-ion electrochemical storage

In the present work, particles of cobalt hexacyanoferrate (CoHCF) were deposited on reticulated vitreous carbon (RVC) foam surface to overcome the lack of conductivity of CoHCF and take advantage of their capacity for Na+ ions storage. The deposition was carried out through direct formation of the CoHCF by cyclic voltammetry, and the chemical transformation of cobalt hydroxide and cobalt hydroxide carbonate films obtained by electrochemical and hydrothermal synthesis, respectively, to CoHCF by immersion in an aqueous solution containing [Fe(CN)6]3- ions. The prepared composites were characterized through FTIR, Raman, XRD and SEM-EDS techniques to obtain information about their morphology, composition and structure. The results indicated that the employ of RVC foam leads to well-distributed CoHCF particles connected to its surface, offering abundant sites for ion-storage. Moreover, their electrochemical performance was evaluated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). Benefiting from the highly conductive substrate, the charge storage mechanism of CoHCF and RVC, and the lower impedance originated at the CoHCF/RVC interface, the composites exhibited an enhanced performance at high potential scan rates or charge and discharge rates. Notably, improved electrochemical utilization of CoHCF was reached through the methods based on cobalt precursors, such composites displayed higher storage capacity. The CoHCF(-1.1 V)/RVC electrode synthesized by electrochemical-chemical synthesis exhibits a high specific capacity of 816 mC cm−3 at 0.25 mA cm−3 and 36% (296 mC cm−3) of its initial capacity was maintained at 5 mA cm−3, which improves 2.8 times the capacity achieved by CoHCF(50 mVs−1)/RVC through electrochemical strategy and the 19% of capacity retention from CoHCF(1 mmol)/RVC composite prepared by the hydrothermal-chemical method. Therefore, the CoHCF(-1.1 V)/RVC electrode can be potentially employed as a cathode in the recent sodium-ion batteries technology.

Alkyl-group grafting onto glassy carbon cathodes by reduction of primary monohaloalkanes: electrochemistry and X-ray photoelectron spectroscopy studies

Surface alkylation of glassy carbon (GC) and reticulated vitreous carbon (RVC) cathodes can occur when a primary alkyl monohalide is present in solution and when the electrode is polarized at potentials more negative than those required for reductive cleavage of the carbon–halogen bond, leading to the grafting of alkyl moieties onto the surface of the carbon cathode. Examination of electrode surfaces by means of X-ray photoelectron spectroscopy (XPS) has revealed that surface sp2:sp3 carbon ratios are approximately 4:1 for both pristine GC and RVC electrode materials that are commercially available. Further XPS analysis of these electrodes before and after reduction of perfluorobutyl iodide (C4F9I) provides substantial supporting evidence for a previously proposed mechanism for the grafting process that involves an SN2-like reaction between sp2-hybridized carbon (nucleophile) of the cathode and primary alkyl halides (electrophile) leading to conversion of sp2 sites to sp3 sites, with final surface sp2:sp3 carbon ratios that fall below 1:1. At the end of this paper, we discuss (mainly in qualitative terms) the ramifications of this surface modification of GC and RVC electrodes with respect to (a) bulk reduction of primary alkyl halides and (b) use and behavior of a well-known catalyst precursor (1,2,4,5-tetracyanobenzene).

Improvement in Electrode Performance of Novel SWCNT Loaded Three-Dimensional Porous RVC Composite Electrodes by Electrochemical Deposition Method.

The three-dimensional (3D) composite electrodes were prepared by depositing different amounts of acid-functionalized single-walled carbon nanotubes (a-SWCNTs) on porous reticulated vitreous carbon (RVC) through the electrochemical deposition method. The SWCNT was functionalized by the reflux method in nitric acid and was proven by Raman and visible spectra. The optimum time for sonication to disperse the functionalized SWCNT (a-SWCNT) in dimethyl formamide (DMF) well was determined by UV spectra. The average pore size of RVC electrodes was calculated from scanning electron microscopy (SEM) images. Moreover, the surface morphology of composite electrodes was also examined by SEM study. All 3D electrodes were evaluated for their electrochemical properties by cyclic voltammetry. The result showed that the value of specific capacitance of the electrode increases with the increase in the amount of a-SWCNT in geometric volume. However, the value of specific capacitance per gram decreases with the increase in scan rate as well as the amount of a-SWCNT. The stability of the electrodes was also tested. This revealed that all the electrodes were stable; however, lower a-SWCNT-loaded electrodes had excellent cyclic stability. These results suggest that the a-SWCNT-coated RVC electrodes have promise as an effective technology for desalination.

A Strategy to Enhance the Electrode Performance of Novel Three-Dimensional PEDOT/RVC Composites by Electrochemical Deposition Method.

In this article, three-dimensional (3D) microstuctured poly(3,4-ethylenedioxythiophene) (PEDOT)/reticulated vitreous carbon (RVC) composite electrodes with varying amount of PEDOT loadings were successfully prepared by electrochemical deposition method. The composites were characterized by Raman spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and cyclic voltammetry. Raman spectra suggest that there is a strong interaction between the RVC and backbone of PEDOT chain. It is revealed from the SEM images that the PEDOT amount, thickness, surface roughness, porosity, and globular structure on RVC electrode are increased with the increase in polymerization time. The capacitance of PEDOT/RVC electrode has increased by a factor of 2230 compared to a bare RVC electrode when polymerization is carried out for 120 min. Moreover, the capacitance of PEDOT was found to be very high compared with other PEDOT studies. The electrodes also show good cyclic stability. This substantial increase in capacitance of RVC electrode is due to the rough, highly porous, and honeycomb-like fine structure of PEDOT coating, which shows a flower-like morphology, consisting of numerous thin flakes with numbers of macropores and micropores. This interesting morphology has enhanced the performance of PEDOT because of increased electrode surface area, specific capacitance, and macroporous structure of RVC electrode.

Electrochemical degradation of RB-5 dye by anodic oxidation, electro-Fenton and by combining anodic oxidation–electro-Fenton in a filter-press flow cell

This paper reports the removal of a recalcitrant and toxic dye, Reactive Black 5 (RB-5) by three methods; 1) anodic oxidation (AO) on Boron-Doped Diamond (BDD), 2) by electro-Fenton (EF) process where hydrogen peroxide was produced by oxygen reduction on reticulated vitreous carbon (RVC) electrodes and 3) by the combination of AO–EF. The BDD and RVC electrodes were fitted in a filter-press flow cell in recycle batch mode of operation. The experimental set-up for the AO and EF processes consisted of two electrolyte compartments separated by a Nafion membrane with the dye contained in the anolyte and the catholyte, respectively. The combined AO–EF process used only one electrolyte compartment. The colour and total organic carbon (TOC) removal were more efficient when the AO and EF processes were used separately than the combined process, AO–EF. The influence of current density and initial concentration of ferrous ions were examined. The lowest energy efficiency (208kWhkg−1) with the EF process was found when −0.4V vs. Ag/AgCl was applied to a RVC electrode and the concentration of Fe2+ was 1.0×10−4moldm−3 achieving total colour and 74% of TOC removals in less than 90min electrolysis. All proposed processes were able to promote high percentages of TOC removal following a pseudo-first order kinetic oxidation. The BDD electrode was the most effective material to remove RB-5 dye within 7.5min and presented the highest apparent rate constant (0.835min−1) with 82% TOC removal within 30min at an energy consumption of 291kWhkg−1 and 41.1mAcm−2 current density. In the case of the combined process AO–EF the electrodegradation rate of RB-5 was at least three times lower, apparent rate constant (0.269min−1), and 32% of TOC was removed with a high EC (682kWhkg−1). Therefore oxidation process applied separately was more efficient.

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

Composites formed from diamond grown on carbonaceous materials have been showed special attention due to their remarkable properties for electrochemical applications. In this sense, boron-doped nanocrystalline diamond (BDND) films were grown on reticulated vitreous carbon (RVC) substrates produced from poly(furfuryl alcohol) at two heat treatment temperatures (HTT) of 1000 °C and 1700 °C. The films were produced from hot filament chemical vapor deposition reactor with an in-situ doping process in the gas phase. Scanning electron microscopy and Raman spectroscopy analyses confirmed that both RVC electrodes were totally covered by good quality nanodiamond coatings with acceptor concentrations at around 1020 B.cm-3, evaluated by Mott-Shottky measurements. Both RVC/BDND composites presented good electrochemical response in redox couple. Nonetheless, RVC/BDND1700 showed the best conductivity due to its lowest variation of ΔEp value as well as its highest electrochemical area. These results demonstrate that RVC/BDND1700 is a very promising electrode material.

Treatment of Reticulated Vitreous Carbon by Dielectric Barrier Discharge Plasma for Electrodes Production

This paper deals with the surface modification of reticulated vitreous carbon (RVC) by dielectric barrier discharge (DBD) for electrodes production. RVC samples were exposed to air-DBD plasma for 5.0 and 10.0 min. Following the treatment, the specimens were characterized by scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), contact angle measurements, and electrochemical analyses [cyclic voltammetry (CV)]. The SEM images show an alteration of the RVC surface morphology because of the surface etching during the DBD processing. This finding is in agreement with the enhanced specific electrochemical surface area of RVC electrodes, which is related to an increase of its surface roughness. In addition, a slight increase of the oxygen content on the surface was confirmed by XPS analysis. Therefore, the RVC surface became more hydrophilic as detected by water contact angle measurements. For corroborating this statement, a solid monolithic vitreous carbon was used for this test. An increase in the anodic charge of the RVC electrodes due to the surface oxidation was also observed. Raman spectra showed insignificant changes in the material crystalline structure.

Quantitative Measurement of Electrochemically Induced DNA Damage Using Capillary Electrophoresis

Exposure of mammalian cells to oxidative stress can result in DNA damage that adversely affects many cell processes. We used bulk electrolysis in an electrochemical system and capillary electrophoresis (CE) to control and measure the effect of oxidative stress on DNA. Calf thymus DNA and a fluorescently labeled DNA sizing ladder were subjected to fixed oxidizing potentials using a reticulated vitreous carbon electrode (RVC) and their fragmentation was measured with the use of CE. The resulting electropherograms showed that the oxidative treatment resulted in DNA fragmentation. Poly adenosine (Poly A) 40mer and poly guanosine (Poly G) 40-mer oligonucleotides were exposed to a controlled oxidative environment at constant potential values E = 0.5 V, 1.0 V, 1.5 V, and 2 V (vs Ag/AgCl) for 1 hour in 0.1 mol/L potassium phosphate buffer pH 7.3. The treated DNA fragments were analyzed by CE. The areas of the CE peaks were measured and the percentage of DNA fragmentation was calculated. Only minor fragmentation was observed when oligonucleotides were exposed to E = 0.5 V, with strand scission starting at electrode potentials E > 1.0 V. The E = 2.0 V treatment resulted in approximately 50% fragmentation of Poly A, compared to approximately 15% for the Poly G. These results, using DNA as a test model, demonstrate that controlled-potential electrolysis can be used to produce desired levels of oxidative damage to biomaterials without the need to use oxidative chemicals, which are difficult to control and relate to thermodynamic models.

Early detection of Candida albicans biofilms at porous electrodes

We describe the development of an electrochemical sensor for early detection of biofilm using Candida albicans. The electrochemical sensor used the ability of biofilms to accept electrons from redox mediators relative to the number of metabolically active cells present. Cyclic voltammetry and differential pulse voltammetry techniques were used to monitor the redox reaction of K3Fe(CN)6 at porous reticulated vitreous carbon (RVC) (238.7cm2) working electrodes versus Ag/AgCl reference. A shift in the peak potential occurred after 12h of film growth, which is attributed to the presence of C. albicans. Moreover, the intensity of the ferricyanide reduction peak first increased as C. albicans deposited onto the porous electrodes at various growth times. The peak current subsequently decreased at extended periods of growth of 48h. The reduction in peak current was attributed to the biofilm reaching its maximum growth thickness, which correlated with the maximum number of metabolically active cells. The observed diffusion coefficients for the bare RVC and biofilm-coated electrodes were 2.2×10−3 and 7.0×10−6cm2/s, respectively. The increase in diffusivity from the bare electrode to the biofilm-coated electrode indicated some enhancement of electron transfer mediated by the biofilm to the porous electrode. Verification of the growth of biofilm was achieved using scanning electron microcopy and laser scanning confocal imaging microscopy. Validation with conventional plating techniques confirmed that the correlation (R2=0.9392) could be achieved between the electrochemical sensors data and colony-forming units.

On-line removal of redox-active interferents by a porous electrode before amperometric blood glucose determination

A porous reticulated vitreous carbon (RVC) electrode and a disk electrode coupled in tandem in an electrochemical flow cell has been used for electrolytic removal of interferents before amperometric glucose detection. The electrolytic efficiency at the upstream RVC electrode is 100% at a flow rate of 0.1mLmin−1 or lower. Potential interferents such as acetaminophen, ascorbic acid, and uric acid can be completely eliminated by electrolysis at the RVC electrode. A mixed monolayer comprising glucose oxidase (GOD) and ferrocenyl-1-undecanethiol preformed at the downstream gold disk electrode was used as a mediator-based amperometric glucose sensor. The dependence of the amperometric current on the glucose concentration exhibits good linearity across over three orders of magnitude. The glucose measurements were also found to be reproducible (RSD<3.5%) and accurate. Unlike the chemiluminescence method, this device obviates the use of carcinogenic substrates and the glucose sensor performance is independent of the oxygen present in sample. On the basis that the RVC electrode requires minimal cleanup and the GOD-modified electrode remains stable for a week, the electrochemical flow cell should be amenable for automated on-line removal of redox interferents for other types of enzyme-based biosensors.

A mathematical model to predict the electrode potential profile inside a polyaniline-modified reticulate vitreous carbon electrode operating in the potentiostatic reduction of Cr(VI)

Hexavalent chromium compounds are very toxic and commonly found in the effluents of several industrial processes. Its reduction to the trivalent state is necessary in order to facilitate its removal from aqueous effluents using chemical precipitation or adsorption. The electrochemical process using conducting polymers deposited on reticulated vitreous carbon (RVC) has been considered as a promising alternative to chemical methods. In this work a polyaniline-modified RVC electrode was used in a potentiostatic process to reduce Cr(VI) to Cr(III). Two mathematical models considering a PFR and CSTR reactors were used to determine the mass transfer coefficients from the experimental concentration–time curves. The potential distribution was also measured and compared with the values obtained from a mathematical model. The effective conductivity and tortuosity were also determined. Approximately 80% of the Cr(VI) was reduced to its trivalent form during fifty minutes of electrolysis, giving an overall current efficiency and energy consumption of 0.71 and 4.4 kWh kg −1, respectively. The high correlation coefficients ( R 2 > 0.999) obtained using PFR and CSTR models confirmed that the assumption of limiting current ( I L ) kinetics can be effectively used to describe the potentiostatic reduction. Additionally, k m determined by CSTR, PFR and I L equations had practically the same value. However, the tortuosity must be considered in the mathematical model to accordingly predict the potential profile.

Production of a bio-compatible metallic implant via electropolymetrization method by coating a synthetic hydrogel on a titanium alloy

Recently, titanium implants are used to solve many different health problems. Features of titanium, such as lightness, strength, high corrosion resistance and bio-compatibility have increased the usage of titanium in bio-materials. Titanium plates take an important role, especially in integrating bone fractures. Although titanium implants are essential materials for this purpose, to minimize the risks during healing period, bio-active titanium surfaces are desired. The aim of this study is to coat titanium alloy (Ti–6Al–4V) which is used as an implant material with a synthetic bio-compatible hydrogel, poly(HEMA–GDMA), by electropolymerization method in order to develop the functionality and the bio-compatibility of the material. In order to improve the adhesion of the coatings to the metal surface, first titanium working electrodes, were encapsulated in bakelite as circular plates and polished flat to a 3 μm finish. Then, each electrode was cleaned in an ultrasonic bath using ethanol for 10 min, rinsed with water and dried. All potentiostatic coating experiments were carried out using a potentiostat–galvanostat and an H-type glass cell. In the cell, (NH 4 ) 2 S 2 O 8 and H 2 SO 4 were used as the initiators of the electropolymerization where HEMA was the monomer and GDMA was the crosslinker. Na 2 SO 4 was also added to increase the conductivity of the solution as well as the thickness of the coatings. Titanium alloy (Ti 6 Al 4 V), reticulated vitreous carbon electrode (RVC) and saturated calomel electrode (SCE) were chosen as working electrode, counter electrode, and reference electrode, respectively. The electrochemical cell was purged with nitrogen for 30 min before any potential was applied. Then potential was ramped at 1 mV/s from 0 V (vs. SCE) to the desired potential and held for 30 min. During the electropolymerization, nitrogen purging was continued. First optimum coating conditions were determined in terms of applied potential, initiators, monomer and cross-linker concentrations. Then the surface morphologies of the coatings were examined by optical microscope and scanning electron microscope (SEM), the chemical characterizations were done using Fourier Transform Infrared Spectroscopy (FT-IR). Surface roughness and thickness of the coatings were obtained by the surface profilometer device. As a result, white and opaque coatings of poly(HEMA–GDMA) were produced uniformly on Ti 6 Al 4 V cathodes via electropolymerization method. Hazy surfaces of the coatings indicate the diffusion of light on reflectance as a result of rough surface morphology. Na 2 SO 4 addition is important as it increases the conductivity leading to thicker coatings.

The preparation of PbO2 coatings on reticulated vitreous carbon for the electro-oxidation of organic pollutants

The preparation of PbO2 coatings on reticulated vitreous carbon (RVC) has been carried out at constant current from electrolytic baths containing aqueous Pb(II) and methanesulfonic acid (MSA, CH3SO3H). The morphological and structural analysis of the RVC/PbO2 deposits carried out by scanning electron microscopy (SEM) and X-ray diffraction revealed that a thick (100μm), homogeneous, nanostructured β-PbO2 film can be successfully formed. As a result, three-dimensional β-PbO2 structures were obtained, being particularly interesting for their use as anodes in wastewater treatment. The high oxidation ability of these anodes has been verified by the electro-oxidation of Methyl Orange aqueous solutions. Quick decolourisation was achieved, with total colour removal in less than 60min at 600mA due to the production of large amounts of reactive OH radicals from the oxidation of water at high anodic potentials. The progressive mineralisation of the solutions was also ascertained from the total organic carbon (TOC) removal, which was much quicker at a higher applied current. All the coated RVC electrodes exhibited excellent long-term stability and remained unaltered after prolonged electrolyses. In addition, novel PbO2 composite coatings were prepared in the presence of hydrothermally synthesized titanate nanotubes (TiNT). The SEM images showed the presence of TiNT agglomerates along the PbO2 surface, which led to higher anodic current in the cyclic voltammetries carried out with Methyl Orange solutions. It is suggested that TiNT favour the adsorption of the organic molecules, facilitating the contact with the OH radicals and thus accelerating the electro-oxidation process. This was confirmed by the faster TOC removal compared to that yielded by the RVC/PbO2, being 45% instead of 24% at 120min.

Bismuth‐Coated Reticulated Vitreous Carbon and Bismuth‐Coated Glassy Carbon Electrodes for On‐Line Coupling of ASV with ICP‐MS

AbstractAnodic stripping voltammetry (ASV) has been combined on‐line with inductively coupled plasma‐mass spectrometry (ICP‐MS) using both Bi‐coated reticulated vitreous carbon (RVC) and Bi‐coated glassy carbon (GC) disk electrodes. Because the same flow cell is used for the RVC and GC disk electrodes, the analytical performances between these two types of Bi‐coated electrodes can be accurately compared for their utilizations in the ASV‐ICP‐MS technique. Comparison of the performances includes signal enhancement, reproducibility, dynamic range, and hydrodynamic stability of the Bi coating. The results indicate that the signal enhancement produced by the Bi‐coated RVC electrode (in the flow‐through configuration) is greater, while the hydrodynamic stability of the Bi‐coated GC disk electrode is better. Both types of electrodes were found to be highly effective in eliminating the matrix effects that are detrimental to ICP‐MS analysis. For the purpose of metal preconcentration, Bi has similar properties to Hg (e.g., high hydrogen overpotential and ability to accumulate a range of analytes). However, the Bi film is more robust than the Hg film in a flow system and, unlike Hg2+, Bi3+ in the solution does not cause the memory effect (i.e., it does not adhere onto glass nebulizer and spray chamber of ICP over a long period of time). The nontoxicity of bismuth also makes it an environmentally friendly alternative to mercury for coupling ASV on‐line with ICP‐based techniques.

Copper deposition at segmented, reticulated vitreous carbon cathode in Hull cell

The electrodeposition of copper from an acid sulphate solution has been studied in a Hull cell fitted with four types of cathode; a carbon plate or a reticulated vitreous carbon (RVC) sheet was used either in a continuous or segmented form. The rates of mass transport to the planar plate and RVC electrodes have been compared in static and stirred electrolytes containing 50, 75 and 100 mmol dm–3 CuSO4 in 0·5 mol dm–3 Na2SO4 at pH 2 and 298 K. The cathodes were divided into 10 equal sections and current vs. potential curves were obtained for each section at a constant current up to 140 mA. The current distribution over the cathodes followed a logarithmic decay with distance along the cathode; segments nearest to the anode experienced the highest rate of copper deposition.

Evaluation of non-specific binding suppression schemes for neutravidin and alkaline phosphatase at the surface of reticulated vitreous carbon electrodes

Non-specific binding (NSB) of high-molecular-weight proteins onto electrode surfaces can complicate the application of electroanalytical techniques to clinical and environmental research, particularly in biosensor applications. We present herein various strategies to modify the surface of reticulated vitreous carbon (RVC) electrodes to suppress non-specific binding of biomolecules onto its surface. Non-specific binding and specific binding (SB) of two enzyme conjugates, neutravidin-alkaline phosphatase (NA-ALP) and biotinylated alkaline phosphatase (B-ALP), and also neutravidin itself, were studied using hydroquinone diphosphate (HQDP) as an enzyme substrate for ALP inside the pores of RVC electrodes that had been subjected to various modification schemes. The extent of NSB and SB of these biomolecules inside RVC pores was assessed by measuring the initial rate of generation of an electroactive product, hydroquinone (HQ), of the enzyme-catalyzed reaction, using linear scan voltammetry (LSV) for HQ detection. Electrodes functionalized with phenylacetic acid and poly(ethylene glycol) (PEG) showed low NSB and high SB (when biotin capture ligands were included in the modification scheme) in comparison with unmodified electrodes and RVC electrodes modified in other ways. A simple sandwich bioassay for neutravidin was performed on the RVC electrode with the lowest NSB. A concentration detection limit of 52+/-2 ng mL(-1) and an absolute detection limit of 5.2+/-0.2 ng were achieved for neutravidin when this assay was performed using a 100 microL sample size.