Glassy Carbon Electrode Substrate Research Articles

Enzalutamide-human serum albumin interaction: Electrochemical exploration of complex formation and binding parameters

This research investigation employed electrochemical methods to explore the interaction between the anti-cancer drug Enzalutamide (ENZ) and Human Serum Albumin (HSA). Cyclic Voltammetry (CV), Differential Pulse Voltammetry (DPV), and Electrochemical Impedance Spectroscopy (EIS) techniques were used via a glassy carbon electrode (GCE) substrate. The interaction between ENZ and HSA was examined based on the changes in the electrochemical behavior of [Fe(CN)6]3−/4− redox species under physiological pH conditions. Electrochemical and kinetic parameters of the redox probe in the presence of HSA, ENZ, and the ENZ-HSA complex were calculated. The results showed significant differences in these parameters due to the formation of an electro-inactive complex between the protein and the drug. Binding parameters of ENZ-HSA, such as the binding constant and complex stoichiometry, were found, revealing the formation of a robust drug-albumin complex with a binding constant value of 2.7 × 108 M−1. A molecular docking study was conducted to examine the possible binding mode of ENZ and its interactions with HSA. This research provides valuable insights and can serve as a reference for future studies to enhance drug delivery systems.

Novel solid-contact ion-selective electrode based on a polyaniline transducer layer for determination of alcaftadine in biological fluid.

Fabrication of a novel ion selective electrode for determining alcaftadine was achieved. The glassy carbon electrode (GCE) was utilized as a substrate in fabrication of an electrochemical sensor containing polyaniline (PANI) as an ion-to-electron transducer layer. A PVC polymeric matrix and nitrophenyl-octyl-ether were employed in designing the ion-sensing membrane (ISM). Potential stability was improved and minimization of electrical signal drift was achieved for inhibition of water layer formation at the electrode interface. Potential stability was achieved by inclusion of PANI between the electronic substrate and the ion-sensing membrane. The sensor's performance was evaluated following IUPAC recommendations. The sensor dynamic linear range was from 1.0 × 10-2 to 1.0 × 10-6 mol L-1 and it had a 6.3 × 10-7 mol L-1 detection limit. The selectivity and capabilities of the formed alcaftadine sensor were tested in the presence of its pharmaceutical formulation excipients as well as its degradation products. Additionally, the sensor was capable of quantifying the studied drug in a rabbit aqueous humor. Method's greenness profile was evaluated by the means of Analytical Greenness (AGREE) metric assessment tool.

Design & Characterization of Pb Electrode for Sensing Trichloroethylene in Ionic Liquid/Acetonitrile Co-Solvents

Design & Characterization of Pb Electrode for Sensing Trichloroethylene in Ionic Liquid/Acetonitrile Co-Solvents

Carbon Electrocatalysts for High Performance Bromine and Iodine Redox Flow Battery Electrodes

Redox flow battery (RFB) electrodes act as bi-directional electrocatalysts, improving the kinetics of the electrolyte redox reactions of interest without being consumed in the reaction itself. This property of flow battery electrodes allows for the power and energy densities of RFBs to be uncoupled and designed separately. The power density is largely dependent on the activity of the electrocatalyst, whereas the energy density is determined by the solubility and volume of the electroactive species in the external electrolyte tank. Due to the advantages of RFBs, they have been heavily studied and implemented for applications in large-scale energy storage and are often used in tandem with renewable energy stations. Zinc-bromine flow batteries have arguably become the most promising and common flow battery technology behind that of the all-vanadium RFB, but are held back by low power densities that result from the slower Br2/Br- half-cell kinetics compared to that of the Zn2+/Zn half-cell. Fabrication of low-cost, high activity bromine electrodes will help increase the viability of this technology. Analogous zinc-iodine flow batteries have also been proposed for identical applications, as the electrolyte is much less toxic and corrosive to common battery materials than bromine, and a high solubility of electroactive species due to the formation of the triiodide ion (I3 -) (up to ~12 M). In addition, some scientific research has shifted towards flow batteries constructed from heteropolyhalides (such as I2Br- or Br2Cl-) by combining different halogen electrolytes.We investigated a variety of different carbon electrocatalysts for low-cost and durable electrodes for the I2/I-, Br2/Br, and mixed heteropolyhalide electrodes in RFB technology. A variety of carbon blacks, graphenes, and phosphorus-doped graphitic carbons (PCx) were drop-casted onto a glassy carbon electrode substrate and their electrocatalytic performance was assessed via a variety of techniques including cyclic voltammetry, rotating disc studies, and impedance spectroscopy. Phosphorus-doped graphitic carbon (PCx) was synthesized via the reaction of phosphorus chloride and benzene in different volumes ratios to obtain samples with variable amounts of phosphorus content (PC, PC3, PC5, PC8), characterized by X-ray diffraction analysis and 31P NMR.The electrochemical performance of various carbon blacks and graphenes were observed to have a strong dependence on their surface area and porosity. The electrocatalytic activity of the phosphorus-doped catalysts was seen to exhibit a volcano plot relationship with the degree of phosphorus-doping, where PC5 and PC3 exhibited higher electrocatalytic behaviour towards the halogen/halide redox reactions than PC and PC8. These observations can be explained by P31 NMR indicating an increased amount of P-O bonds with increasing amounts of doping, with the oxygen containing functional group being catalytic. Excessive doping leads to faults in the lattice structure of the P-doped graphite. The surface area of the electrocatalyst material had the largest impact overall on the electrocatalytic performance of the electrode.

Carbon Electrocatalysts for High Performance Bromine and Iodine Redox Flow Battery Electrodes

Redox flow battery (RFB) electrodes act as bi-functional electrocatalysts, improving the kinetics of the redox reactions of interest without being consumed in the reaction itself. This property of flow batteries allows them to be fully discharged without damaging the electrode, and also allows for the power and energy densities of RFBs to be uncoupled and designed separately. The power density is largely dependent on the activity of the electrocatalyst, whereas the energy density is determined by the solubility of the electroactive species in the external electrolyte tank. Due to the advantages of RFBs, they have been heavily studied and implemented for applications in large-scale energy storage and are often used in tandem with renewable energy sources. Zinc-bromine hybrid flow batteries have arguably become the most promising and common flow battery technology behind that of the all-vanadium RFB, but are held back by low power densities that result from the slower Br2/Br- half-cell kinetics compared to that of the Zn2+/Zn half-cell. Analogous zinc-iodine based flow batteries have recently become the subject of much scientific interest as well, as the electrolyte is less toxic and corrosive to common battery materials compared to bromine, and a high concentration of electroactive species can be achieved due to the formation of the triiodide ion (I3 -) (up to ~12 M). In addition, some scientific research has recently shifted towards flow batteries constructed from heteropolyhalides (such as I2Br-or Br2Cl-) by combining different halogen-based electrolytes. Flow batteries constructed with Br2/Br-and I2/I-half-cells have been able to achieve some of the highest energy densities reported for aqueous flow batteries to date, but improvements still need to be made to the electrode materials.We investigated a variety of different carbon electrocatalysts for fabrication of low-cost and durable electrodes for the I2/I-, Br2/Br-, and heteropolyhalide redox couples in RFB technology. A variety of carbon blacks and phosphorus-doped graphitic carbons (PCx) were drop-casted onto a glassy carbon electrode substrate and their electrocatalytic performance was assessed via a variety of techniques including cyclic voltammetry, rotating disc electrode studies, and electrochemical impedance spectroscopy. Phosphorus-doped graphitic carbon was synthesized via the reaction of phosphorus chloride and benzene in different volumes ratios to obtain samples with variable amounts of phosphorus content (PC, PC3, PC5, PC8), characterized by X-ray diffraction analysis and 31P NMR.The electrocatalytic activity of various carbon blacks had a strong dependence on their surface area and porosity. The electrocatalytic activity of the phosphorus-doped graphitic carbons exhibit a bell curve relationship with the degree of phosphorus-doping, where PC5 and PC3 exhibited higher electrocatalytic behaviour towards the halogen/halide redox reactions than PC and PC8. These observations can be explained by 31PNMR indicating an increased amount of P-O bonds with increasing amounts of doping, with the oxygen containing functional group being catalytic. Excessive doping leads to faults in the lattice structure of the P-doped graphite. The surface area of the electrocatalyst material had the largest impact overall on the electrocatalytic performance of the electrode.

Nanostructured Poly(Phenazine)/Fe2O3 nanoparticle film modified electrodes formed by electropolymerization in ethaline - Deep eutectic solvent. Microscopic and electrochemical characterization

Electropolymerization in ethaline deep eutectic solvent (DES) was carried out to prepare three different electroactive polymers on iron oxide nanoparticle modified glassy carbon electrode substrates: poly(neutral red), poly(methylene green), and poly(Nile blue). The electrochemical properties of the novel nanocomposites were studied by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy, and their morphologies were examined using scanning electron microscopy. Electrochemical characterization of the polymer films demonstrated similar voltammetric current response and impedance properties. Analysis of the cyclic voltammograms showed that the electrochemical processes at the polymer film coated electrodes are limited by surface reactions. Scanning electron microscopy images confirmed the results obtained by cyclic voltammetry and electrochemical impedance and showed more uniform and smooth polymer film surfaces produced in ethaline than those prepared in aqueous media, which can give important benefits for sensor and biosensor applications. Catalase enzyme was immobilized on the nanocomposite films, and the resulting biosensors were successfully used for the detection of H2O2, presenting low limits of detection with high repeatability and stability.

Silver nanoparticle-functionalized poly (3, 4-ethylenedioxythiophene): Polystyrene film on glass substrate for electrochemical determination of nitrite

Abstract A high-performance electrochemical sensor based on silver-nanoparticle-functionalized poly (3, 4-ethylenedioxythiophene): polystyrene (PEDOT:PSS) film on the common glass (Ag-CSA-PEDOT:PSS) was constructed by simple electrodeposition. The concentrated sulfuric-acid-treated PEDOT:PSS polymeric (CSA-PEDOT:PSS) film on common glass can be used as an electrode substrate to replace an expensive glassy carbon electrode (GCE). The unique properties of the Ag-CSA-PEDOT:PSS film were investigated using X-ray photoelectron spectroscopy, atomic-force microscopy, X-ray diffractometry, cyclic voltammetry and amperometric i-t. The Ag-CSA-PEDOT:PSS film electrode provides a highly sensitive determination of nitrite compared with indium tin oxide or the GCE substrate. Additional time was not required to polish the GCE surface. The Ag-CSA-PEDOT:PSS film electrode exhibited a broad linear range of 0.5–3400 μM, and had a lower detection limit of 0.34 μM (S/N = 3) in phosphate buffer solutions. Ag-CSA-PEDOT:PSS film electrodes can be used for sample detection of nitrite because they have a strong anti-interference ability, high reproducibility and high long-term stability. The fabrication strategy would provide a promising route to construct the novel electrochemical sensors.

Ammonia-induced synergistic construction of Co3O4@CuO microsheets: An efficient electrocatalyst for oxygen evolution reaction

Copper-based materials have attracted increasing attention for their earth-abundant and cheap characters for water splitting application. In the present work, a combined structure of Co3O4 nanoparticles and CuO microsheets was constructed in an aqueous system and studied as an efficient oxygen evolution reaction (OER) electrocatalyst. NH3 molecules as the ligand of metal ions (Cu2+ and Co2+) played vital roles for the uniform growth of Co3O4@CuO microsheets. The synergetic contribution of the two components made the composite samples behave excellent OER activity and fast kinetics both on glassy carbon electrode (GCE) and nickel foam (NF) substrates in alkaline medium. The remarkable small overpotentials (310 and 394 mV) can be obtained for CuO-Co-0.2/GCE sample at current densities of 1 and 10 mA/cm2 in 1.0 mol L−1 KOH (pH = 13.6). The in-situ deposited CuO-Co-0.2/NF achieved in the aqueous synthetic system demonstrates superior (structural and electrochemical) stability for 20 h-OER performance.

Cold Plasma as an Innovative Construction Method of Voltammetric Biosensor Based on Laccase.

Development of new, faster methods of biosensor construction is a huge challenge for current science and industry. In this work, biosensor construction was carried out using a new soft plasma polymerization (SPP) method in which a bio-recognition layer of laccase enzyme was polymerized and bonded to a glassy carbon electrode (GCE) substrate under atmospheric pressure with a corona discharge jet. Laccase belongs to the oxidoreductase enzyme group with four copper atoms in its active center. Application of the corona SPP plasma method allows reduction of the time needed for biosensor construction from several hours to minutes. The presented work includes optimization of the laccase bio-recognition layer deposition time, structural studies of the deposited laccase layer, as well as study of the fabricated biosensor applicability for the determination of Rutin in real pharmaceutical samples. This method produces a biosensor with two linear ranges from 0.3 μmol/dm3 to 0.5 μmol/dm3 and from 0.8 μmol/dm3 to 16 μmol/dm3 of Rutin concentration. Results shown in this work indicate that application of the one-step, corona SPP method enables biosensor construction with comparable analytical parameters to biosensors fabricated by conventional, multi-step, wet methods.

One-step preparation of microporous Pd@cPIM composite catalyst film for triphasic electrocatalysis

Triphasic microporous materials (containing solid, liquid, and gas) are of interest in electrocatalysis. In this exploratory study, a polymer of intrinsic microporosity (PIM-EA-TB) is impregnated with PdCl42− metal precursor and vacuum‑carbonised to give an electrically conductive microporous heterocarbon with embedded Pd nanoparticles of typically 10–30nm diameter. This microporous composite catalyst is formed (via spin-coating) as “flakes” of typically 100nm thickness and 1 to 20μm diameter that are readily re-deposited onto glassy carbon electrode substrates. Due to the triphasic conditions, Pd@cPIM electrocatalytic reactivity is high but only for gases (H2 oxidation or O2 reduction). This selectivity is observed even in the presence of excess formic acid fuel in the aqueous/liquid phase. The potential for application in membrane-less micro-fuel cells is discussed.

(Keynote) Biofilm-Supported Redox-Polymer-Type Materials for Electrocatalytic Oxygen Reduction of Importance to Biosensing and Bioenergetics

Unique properties of biofilms, which include possibility of extracellular electron transport, specific redox activity and capability to form stable polymeric or hydro-gel like microorganism aggregates adhering to common surfaces (including the glassy carbon electrode substrate), were explored here to form systems analogous to redox-polymer modified electrodes. Growth of biofilms was demonstrated with use of Yersinia enterocolitica, a robust Gram-negative rod-shaped bacteria known to be resistive to pH changes (4-10) and temperature variations (0-40oC). The dynamics of bioelectronic transfers originating from the presence of c-type cytochromes, i.e. heme-containing proteins within the biofilm, were further enhanced by introduction of multi-walled carbon nanotubes. Long-term stability of the biofim-based materials was achieved by impregnating them with porous but rigid conducting polymer, poly(3,4-ethylenodioxythiophene) or PEDOT. The fact that carbon nanotubes were derivatized with the carboxyl-group containing 4-(pyrrole-l-yl) benzoic acid facilitated the materials integrity through electrostatic attractive interactions between anionic carboxyl sites and positively charged domains of conducting polymer (PEDOT) structures. In neutral media, the biofilm-based composite (hybrid) matrices exhibited themselves electrocatalytic activity toward reduction of hydrogen peroxide (with possibility of sensing in the broad range of concentrations) and some activity during electroreduction of oxygen. By immobilization of additional catalytic (cobalt porphyrin) sites, a truly bifunctional electrocatalytic interface capable of significantly enhancing oxygen electroreduction currents was produced. Apparently, the reduction of oxygen (to hydrogen peroxide) was initiated at cobalt porphyrin centers and the further reaction (decomposition of hydrogen peroxide intermediate to water) was continued at c-cytochrome–containing biofilm matrix. These features are of importance to bioenergetics, i.e. to the development of cathodes for biofuel cells or biobatteries.

Glassy Carbon Electrode As a Promising Sensor for Healthcare and Environmental Monitoring

Glassy carbon electrode (GCE) has been explored in the present investigations and applied thereafter for biomedical applications and environmental monitoring. A novel electrochemical approach for the quantitative analysis of methylglyoxal as a biomarker in human plasma has been developed. An electrochemical sensor employing a single walled carbon nanotube modified GCE for the sensitive detection of methylglyoxal is delineated for the first time employing square wave voltammetry. This modified electrode exhibits potent and sustained electron-mediating behavior and a well-defined reduction peak in response to methylglyoxal was observed. The interfering effect of common coexisting metabolites in human whole blood has also been investigated. The developed assay was shown to be specific and sensitive for the analysis of plasma levels of methylglyoxal in healthy volunteer and diabetic patients. A simple, rapid and highly selective method for the determination of the most abundant α-dicarbonyl compound in wine and beer has been developed for the first time by employing square wave voltammetry. A novel electrochemical sensor, based on the electrodeposition of platinum nanoparticles onto single wall carbon nanotubes that were casted on a GCE substrate has been developed. This modified electrode was successfully applied for the quantitative analysis of methylglyoxal in wine and beer samples. The developed sensor possesses advantageous properties such as a high active surface area, stability, and a rapid electron transfer rate, which cumulatively demonstrate high performance toward the electrocatalytic reduction and detection of methylglyoxal. A promising direct and simultaneous electrochemical determination method of phenolic pollutants in wastewater samples was constructed successfully on GCE with advantages being rapid, simple, convenient, sensitive, in situ and inexpensive. The electrochemical characteristics of multi-component phenolic pollutants, such as phenol and 4-nitrophenol were investigated on GCE employing square wave voltammetry technique. Each of them displayed good linear relationship between their oxidation peak currents and their corresponding concentrations in a rather wide range coexisting with the other phenolic pollutant. The effect of different experimental and instrumental parameters such as solution pH and square wave frequency were examined. Square wave voltammetry was employed to investigate the electrochemical characteristic of phenol and 4-nitrophenol at GCE and successfully realize the electrochemical separation and simultaneous determination of multi-component phenols at GCE without any modification for the first time.

Trace level voltammetric determination of lead and cadmium in sediment pore water by a bismuth-oxychloride particle-multiwalled carbon nanotube composite modified glassy carbon electrode

Two multiwalled carbon nanotubes-based composites modified with bismuth and bismuth-oxychloride particles were synthesized and attached to the glassy carbon electrode substrate. The resultant configurations, Bi/MWCNT-GCE and BiOCl/MWNT-GCE, were then characterized with respect to their physicochemical properties and electroanalytical performance in combination with square-wave anodic stripping voltammetry (SWASV). Further, some key experimental conditions and instrumental parameters were optimized; namely: the supporting electrolyte composition, accumulation potential and time, together with the parameters of the SWV-ramp. The respective method with both electrode configurations has then been examined for the trace level determination of Pb2+ and Cd2+ ions and the results compared to those obtained with classical bismuth-film modified GCE. The different intensities of analytical signals obtained at the three electrodes for Pb2+ and Cd2+ vs. the saturated calomel reference electrode had indicated that the nature of the modifiers and the choice of the supporting electrolyte influenced significantly the corresponding stripping signals. The most promising procedure involved the BiOCl/MWCNT-GCE and the acetate buffer (pH 4.0) offering limits of determination of 4.0μgL−1 Cd2+ and 1.9μgL−1 Pb2+ when accumulating for 120s at a potential of −1.20V vs. ref. The BiOCl/MWCNT electrode was tested for the determination of target ions in the pore water of a selected sediment sample and the results agreed well with those obtained by graphite furnace atomic absorption spectrometry.

Anodic electrodeposition of iridium oxide particles on glassy carbon surfaces and their electrochemical/SEM/XPS characterization

In this study an electrodeposition procedure of hydrated Ir(III) and Ir(IV) oxyhydroxide species operating under anodic conditions and directly from aged alkaline solution containing 6mM IrCl63− and 20mM Cl− a ligand specie was defined for the surface modification of the glassy carbon electrode substrates. Optimum efficiency of iridium oxide deposition was obtained by cycling the potentials (100mVs−1) between −0.7V and 1.0V vs. SCE. The SEM analysis reveals that the iridium oxide is uniformly distributed on the entire electrode surface with particles having a globular form. All particles, appear isolated or in aggregated structures with an average diameter comprised between 0.03μm and 0.4μm. The XPS curve fitting analysis reveals that the surface deposit is formed of hydrated Ir(III) and Ir(IV) oxyhydroxide species. The electrocatalytic activity of the GC/IrOx electrode toward the oxidation of semicarbazide under acidic condition (i.e., 50mM HClO4) using cyclic voltammetry and chronoamperometry, was also investigated.

Redox-induced solid-solid state transformation of tetrathiafulvalene (TTF) microcrystals into mixed-valence and π-dimers in the presence of nitrate anions

Tetrathiafulvalene (TTF), when dissolved in an organic solvent, can be electrochemically oxidized to the cation radical TTF+• and the dication TTF2+. In aqueous Co(NO3)2 electrolyte media, TTF chemically modified electrodes undergo a very different TTF to TTF+•pathway to give two solid-solid state conversion reactions. Initially, the mixed-valent (TTF)2NO3, containing (TTF-TTF+•) as a dimeric cation, is formed, which in turn can be oxidized to (TTF)2(NO3)2, containing the (TTF+•)2 dimeric cation. These processes occur by nucleation-growth mechanisms on glassy carbon, platinum, gold and indium-tin oxide electrode substrates containing adhered TTF solid. The products have been characterized by spectroscopic and voltammetric methods and (TTF)2(NO3)2 also has been synthesized by reaction of TTF+•, prepared by bulk electrolysis in acetonitrile with (Bu4N)NO3, using the appropriate stoichiometric molar ratios.

Simultaneous determination of hydrazine and phenyl hydrazine using 4′-(4-carboxyphenyl)-2,2′:6′,2″ terpyridine diacetonitrile triphenylphosphine ruthenium(II) tetrafluoroborate complex functionalized multiwalled carbon nanotubes modified electrode

A nanocomposite based on the incorporation of the complex 4′-(4-carboxyphenyl)-2,2′:6′,2″ terpyridine triphenylphosphine diacetonitrile ruthenium(II) tetrafluoroborate with multiwalled carbon nanotubes and ionomer supported upon a glassy carbon electrode substrate is reported and characterized with scanning electron microscopy, transmission electron microscopy and infrared spectroscopy. The electrochemical behavior and stability of the composite electrode was investigated via cyclic voltammetry. The modified electrode exhibits an electro-catalytic activity towards the oxidation of both hydrazine and phenyl hydrazine in 0.1M phosphate buffer solution (PBS, pH 7.4). The oxidation of hydrazine and phenyl hydrazine occurs at 0.81V and 0.32V with limit of detection found to be 3.7×10−7M and 1.15×10−7M and having a linear range from 5×10−6M to 6.5×10−3M, and 5×10−6M to 0.2×10−3M, respectively.

Comparative Studies on Electrocatalytic Activities of Electrochemically and Chemically Reduced Graphene Oxide Noncovalently Modified with Tetrathiafulvalene for Glucose Biosensing

Graphene, a two-dimensional nanomaterial, constitutes a new carbon comprising layers of carbon atoms arranged in six-membered rings [1]. It has attracted intense attention due to its unique electronic, thermal and mechanical properties. Graphene possesses a high ratio of surface area, a good conductivity and mechanical properties comparable with (or even better) than carbon nanotubes. Owing to its inert chemical property and highly hydrophobic surface, graphene is considered as an ideal support for redox mediators via π-π stacking interactions [2].Many chemical methods have been developed for the preparation of graphene, such as epitaxial growth on silicon carbide and chemical reduction of graphene oxide (GO). As the oxidized form of graphene, GO could be easily obtained via a simple chemical processing of graphite. GO contains a range of reactive oxygen containing functional groups, which endows it water solubility and possibility for further biological applications. However, excess of oxygen may break the sp2structure of graphene, as a result deteriorate its conductivity.In the present work, we have exploited unique characteristics of reduced graphene oxide (GO) (obtained by electrochemical treatments (ERGO) and chemical treatments with hydrazine (CRGO)) to construct the efficient anodic glucose oxidase based bioelectrocatalytic systems of potential utility for biofuel cells and biosensors. A noncovalent modification method of ERGO and CRGO conducting support with a mediator, tetrathiafulvalene (TTF), and the bioelectrocatalytic activities of ERGO-TTF and CRGO-TTF composites with immobilized glucose oxidase toward the oxidation of glucose have been demonstrated.The presence of TTF is expected to facilitate an effective flow of electrons from the redox centers of glucose oxidase to the glassy carbon electrode [3]. TTF and its derivatives constitute a group of redox molecules that were successfully used as redox mediators in enzyme electrochemistry. Due to the existence of hydrophilic cation-exchange domains within Nafion deposits on graphene, capable of retaining soluble TTF+, the overall stability of the our bioelectrocatalytic film has increased. As before, reduced graphene oxide have supported transport of electrons within the bio-electrocatalytic film. On the whole, combination of TTF-graphene and glucose oxidase within the film (deposited onto glassy carbon electrode substrate) has produced a catalytic system capable of effective oxidation of glucose in 0.1 M phosphate buffer (pH=8.0). The formation, morphology, and electrocatalytic reactivity of our bioelectrocatalytic films containing of TTF-modified graphene were examined using cyclic voltammetry, rotating disk voltammetry, FTIR spectroscopy, transmission and scanning electrochemical microscopy.

Nitrogen doped graphene and its derivatives as sensors and efficient direct electron transfer platform for enzyme biosensors

The performance of different sensor/biosensor architectures based on graphene (G), nitrogen doped graphene (NG) and their acidic/basic functionalized derivatives, as well as of polymer composites of NG have been compared, using ascorbate oxidation, and glucose enzymatic oxidation, as model reactions on glassy carbon electrode (GCE) substrates, which led to the choice of NG/GCE as the preferred modified electrode for further applications. Enzymatic and non-enzymatic sensing of hypoxanthine (Hx) and xanthine (X), two intermediates in purine metabolism, with relevance in clinical diagnostics and food chemistry, was investigated. Electrocatalytic oxidation of both Hx and X was achieved at NG/GCE, the sensor exhibiting sensitivities of 1.6 and 1.3mAcm−2mM−1 for Hx and X, respectively. Hx biosensing was carried out at −0.35V vs. Ag/AgCl, the enzymatic mechanism being based on direct regeneration of FAD at NG, the analytical characteristics comparing favorably with other reported XOx biosensors. Application to the analysis of biological samples was demonstrated.

Electrocatalytic Enhancement Effects at Platinized Nanoporous Substrates: Oxidation of Ethanol at PtRu Nanoparticles Dispersed over Rh-Containing ZrO2 Support

Nanostructured platinum is so far the best-known and the most active catalyst for the activation of small organic molecules via their specific adsorption and interfacial dissociation However, the ability of platinum to break effectively the C–C bonds is largely limited by side poisoning effects originating from the strong adsorption of COads on Pt surfaces at low (below 60 or even 80 oC). Several two-carbon containing molecules have been reported as undesirable intermediates during ethanol oxidation at polycrystalline Pt, most of them requiring relatively high potentials for complete oxidation.It is commonly accepted that the highest efficiency for electrooxidation of ethanol was achieved at carbon-supported PtSn (PtSn/C) catalysts and, more recently, very promising result were obtained with PtRh type systems. Despite the relatively good performance of the PtSn/C based anodes, the overall efficiency is still poor when compared to oxidation of hydrogen (at Pt) or even methanol (at PtRu). The main products remain acetaldehyde (2-electron oxidation) and acetic acid (4-electron oxidation) thus further modification of existing catalysts is necessary to obtain higher efficiency. There is a need to remove not only the poisoning CO adsorbates but also to activate the ethanol molecule and to break C-C bonds effectively. More recently, modification of the platinum-based surface is achieved by adding the second additive namely by introducing the second alloying metal.We propose a hybrid electrocatalytic material for oxidation of ethanol utilized PtRu nanoparticles dispersed over thin-films of rhodium-containing zirconia. The system is particularly active when it has been deposited onto such platinized nanoporous substrate as silica-nanosphere-layered solid-assembly. Morphologies of the resulting catalytic surfaces were characterized here using electrochemical techniques as well as transmission and scanning electron microscopies. The enhancement of activity of PtRu nanoparticles (in 0.5 mol dm-3 H2SO4 at room temperature in the presence of ethanol) has been evident from the comparative electrochemical (voltammetric, chronoamperometric) experiments performed with use of Rh-containing and Rh-free ZrO2 films deposited onto platinized nanoporous plates. It is apparent from additional diagnostic chronoamperometric experiments (executed at inert glassy carbon electrode substrates) that electrocatalytic currents measured at potentials as low as 0.3 V (vs. RHE) are significantly larger upon application of zirconia and, particularly, Rh-containing zirconia supports for dispersed PtRu nanoparticles. The results are also consistent with the strong enhancement effect originating from the use of platinized silica-nanosphere-layered solid-assemblies. The overall activation effect may have origin in the existence of large population of hydroxyl groups (from zirconia) in the vicinity of platinum (from PtRu alloy nanoparticles) capable of inducing oxidative removal of passivating CO adsorbates. The presence of rhodium within zirconia seems to not only enhance conductivity but also to interact specifically with the oxide and/or dispersed catalytic centers. By analogy to titania, zirconia may influence activity of ruthenium oxo species in the oxidative removal of passivating (e.g. CO) intermediates. High surface area platinized nanoporous substrates enlarge the overall catalytic active area and, most likely, provide reactive sites for C-C bond breaking in the ethanol molecule.

A graphene oxide/conducting polymer nanocomposite for electrochemical dopamine detection: origin of improved sensitivity and specificity.

Neuromodulatory dopamine (DA) acts as an essential signaling molecule in the central nervous system (CNS), and its dysfunction has been implicated in neurological disorders such as Parkinson's disease and schizophrenia. Due to its inherent redox properties, DA can be detected electrochemically by monitoring changes in current as the molecule is oxidized. Many electrode materials for electrochemical detection have been developed to monitor DA, but properties such as sensitivity and specificity must be optimized. We describe a conducting polymer (CP) nanocomposite of poly(3,4-ethylendioxythiophene) (PEDOT) doped with GO nanosheets, and report its superior DA detection performance over bare glassy carbon electrode (GCE) substrates. The GO/PEDOT electrode exhibits favorable electrical properties such as lowered impedance and increased charge storage capacity. The nanocomposite demonstrates improved sensitivity to the oxidation of DA at its surface. Meanwhile, interference from competing analyte, ascorbic acid (AA), is minimized. Mechanistic studies indicate that electrostatic interactions drive the increased sensitivity toward DA, and improved electrocatalysis of AA oxidation by the nanocomposite enables the selective discrimination of DA signals from those of AA. The described performance of the GO/PEDOT nanocomposite accentuates its promise for improving detection capabilities of electrochemical biosensors for the accurate and reliable detection of DA signals in biological samples.