Surface Modification Of Glassy Carbon Research Articles

Covalent modification of glassy carbon surface via radical-induced grafting from electrochemical oxidation of imine derivatives

The selective surface modification and functionalization methods through organic or inorganic grafting are a permanent challenge for constructing custom-made molecular interfaces with high performance as part of electroactive surfaces. We report the novel use of imine derivatives as a source of radical species for modifying a glassy carbon (GC) surface using electrochemical grafting. Based on the above work related to imine compounds, we designed and synthesized two structural isomers, ferrocenyl-nitro imine derivatives. These electroactive ferrocenyl and nitro functional groups served as redox signaling. In order to identify which part of the imine derivatives was grafted on the GC surface, they were subjected to electrolysis at a constant potential to monitor changes in its imine fragment response. Electrochemical and spectroelectrochemical results suggested that just one of two synthesized isomers (η5-C5H4-CH=N-C6H4-NO2)Fe(η5-C5H5) produced a radical species by electrochemical oxidation of the imine with bond cleavage. After the electrolysis process, the cyclic voltammetry and spectroscopic studies showed that a covalent modification of GC surfaces took place via forming a new bond from a nitro-aryl species on the GC surface. Due to imine bond cleavage, the ferrocenyl scissioned fragment was lost far from the electrode surface.

Electrochemical Sensing Platform Based on Renewable Carbon Modified with Antimony Nanoparticles for Methylparaben Detection in Personal Care Products

This paper describes for the first time the surface modification of glassy carbon (GC) electrodes with bamboo-based renewable carbon (RC) and antimony nanoparticles (SbNPs) for the determination of methylparaben (MePa) in personal care products (PCPs). The synthesized RC-SbNP material was successfully characterized by scanning electron microcopy, energy-dispersive X-ray spectroscopy and cyclic voltammetry. The proposed sensor was applied in the detection of MePa using the optimized parameters by differential pulse voltammetry (DPV). The analytical range for detection of MePa was 0.2 to 9.0 µmol L−1, with limits of detection and quantification of 0.05 µmol L−1 and 0.16 µmol L−1, respectively. The determination of MePa in real PCP samples was performed using the proposed GC/RC-SbNP sensor by DPV and UV-vis spectrophotometry as comparative methodology. The use of RC-SbNP material for the development of electrochemical sensors brings a fresh approach to low-cost devices for MePa analysis.

Modification of glassy carbon surface using L-cysteine-capped Mn-doped ZnS quantum dots and multi wall carbon nanotube nanocomposite: application to determine hydrazine in water samples

Modification of glassy carbon surface using L-cysteine-capped Mn-doped ZnS quantum dots and multi wall carbon nanotube nanocomposite: application to determine hydrazine in water samples

Surface Modification of Solid Electrodes with Gliadin Biopolymer Film: A Permselective Membrane in Electrochemical Studies

The application of natural materials films for the surface modification of glassy carbon and gold electrodes to enhance their selective sense in the electrochemical detection of organic and inorganic species is a major challenge. In this study, gliadin was extracted from wheat flour and, for the first time, applied as a novel biocompatible permselective modifier film on gold and glassy carbon electrodes for the electrochemical detection of various compounds. The structure and surface morphology of the extracted gliadin were investigated by Fourier transform infrared (FT-IR) spectroscopy and atomic force microscopy (AFM) techniques. AFM and scanning electron microscopy (SEM) showed that porous structures with high nanometric roughness were present in gliadin membranes prepared from the casting solution of gliadin in ethanol. Compared to hydrophobic ions, the capacitance (C) values of electrical double layers of gliadin film modified electrodes for hydrophilic ions were very high. The findings of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) proved high performance of gliadin membrane as permselectcive film for nominated cationic compounds with fast electrochemical kinetics responses in aqueous solutions (PBS, pH = 7). This behavior was verified by circulating solutions containing model compounds from a home-made continuous cell equipped with gliadin-modified polyamide membranes.

A functionalized renewable carbon-based surface for sensor development

This paper describes the surface modification of glassy carbon (GC) electrodes with a bamboo-based renewable carbon (RC) before and after an acid functionalization procedure with a sulfonitric solution (1:3 HNO3/H2SO4). The morphology and structural characterization indicate an increase of functional groups in the functionalized renewable carbon (RCF) surface. The enhanced electroanalytical properties of RC and RCF were evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in two different setups, in the presence of the redox couple ([Fe(CN)6]3−/4−) and escitalopram (EST). The results revealed an enhancement for the electrochemical responses of both inorganic and organic compounds in the electrolyte. Therefore, the use of new carbon-based materials such as renewable carbon for development of electrochemical sensors brings a fresh approach to low-cost device development.

Determination of Tryptophan at Carbon Nanomaterials Modified Glassy Carbon Sensors: A Comparison

The effect of surface modification of glassy carbon (GC) by single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs) and graphene has been studied for the determination of tryptophan (Trp). The surface morphology of the unmodified and modified sensors was characterized by Field Emission Scanning Electron Microscopy(FE-SEM), Electrochemical Impedance Spectroscopy (EIS), square wave voltammetry (SWV) and cyclic voltammetry (CV). The unmodified GCE exhibited an oxidation peak for Trp at 846 mV at pH 7.4, whereas after the modification with SWCNTs/GCE the oxidation peak shifted to less potential at 685 mV. At MWCNTs/GCE and Graphene/GCE, a well-defined anodic peak was observed at 669 mV and 769 mV, respectively for the oxidation of Trp. Under optimum conditions, a linear calibration curve was observed at unmodified GCE in the concentration range of 10–100 μM of Trp with a detection limit of 190 nM. At SWCNTs/GCE, Graphene/GCE and MWCNTs/GCE the detection limits observed were 15.5 nM, 10.3 nM and 4.6 nM, respectively. The oxidation of Trp involved equal number of proton and electron at all the sensors, which was confirmed by pH studies. A comparison of limit of detection indicated that the modified MWCNTs/GCE sensor exhibited best catalytic response for the sensitive determination of Trp.

Electrochemical Surface Modification of Glassy Carbon by Using Mediated Oxidation of Palmitate Anion in Acetonitrile

In this work, it is presented recent advances in modification of carbon surfaces with long alkyl groups by using the mediated oxidation of carboxilates, in this case it was used palmitate (hexadecanoate anion) as substrate and ferrocene as redox catalyst in acetonitrile solutions. It was observed the occurrence of chemical modification of glassy carbon surface in working solutions containing palmitate during the scan rate experiments. The grafting process was confirmed by doing scan cycling in working solution containing 10 mM of palmitate and 1 mM of ferrocene. It was also evidenced the occurrence of physical absorption of electrochemical products by considering slightly changes between the voltammetric current responses of modified carbon electrodes with and without sonication. Additionally, it was recorded the effect of liposomes on the voltametric response of ferrocene on the modified electrode in which the current oxidation of ferrocene is clearly affected by the presence of these macromolecules.

Electrochemical determination of malondialdehyde biomarker in exhaled breath condensate using poly arginine functionalized by graphene quantum dots and chitosan

Background: Lipid peroxidation is a prominent manifestation of free radical activity in biological systems, and it is involved in the development of different diseases such as cancer or cardiovascular and liver diseases. Malondialdehyde (MDA) is globally recognized as a scientifically accepted biomarker of oxidative stress. Due to the significance of MDA as a marker of lipid peroxidation and because of its elevations in various diseases, the assessment of MDA with new and reliable assays, the development of a fast, sensitive, and selective method to detect MDA with simple instruments is necessary. Methods: This study used the electro polymerization of a low toxic and biocompatible polymer with entitle poly arginine-graphene quantum dots-chitosan (PARG-GQDs-CS) as a novel strategy for surface modification of glassy carbon (GC) surface and preparation a new interface for measurement of MDA in human exhaled breath condensate (EBC). Nanocomposite PARG/CS/GQDs the method of precipitation out of place (ex situ) on the electrode surface was prepared. To verify sequestration nanobiopolymer synthesized Scanning electron microscope images (SEM) were recorded. To identify and study the behavior of malondialdehyde electrochemical methods such as cyclic voltammetry and differential pulse voltammetry were used. Results: The scanning electron microscopy (SEM) images indicated immobilization of uniformly CS and GQDs onto PARG film. The modified electrode appeared as an effective electro activity for detection of MDA. Under the optimized analysis conditions and physiological pH, the prepared sensor showed one oxidation processes for MDA at potentials about 1 V vs. Ag/AgCl with a low limit of quantification (LLOQ) 5.94 nM. Conclusion: The Glassy carbon electrod modified by poly-arginine/chitosan/graphene quantum dots, has good electrical activity for Electro-oxidation malondialdehyde that could be due to synergistic effect poly-arginine, graphene quantum dots and chitosan to create many active sites for this purpose.

Electrochemical monitoring of malondialdehyde biomarker in biological samples via electropolymerized amino acid/chitosan nanocomposite.

This study reports on the electropolymerization of a low toxic and biocompatible nanopolymer with entitle poly arginine-graphene quantum dots-chitosan (PARG-GQDs-CS) as a novel strategy for surface modification of glassy carbon surface and preparation of a new interface for measurement of malondialdehyde (MDA) in exhaled breath condensate. Electrochemical deposition, as a well-controlled synthesis procedure, has been used for subsequently layer-by-layer preparation of GQDs-CS nanostructures on a PARG prepolymerized on the surface of glassy carbon electrode using cyclic voltammetry techniques in the regime of -1.5 to 2V. The modified electrode appeared as an effective electroactivity for detection of MDA by using cyclic voltammetry, linear sweep voltammetry, and differential pulse voltammetry. The prepared modified electrode demonstrated a noticeably good activity for electrooxidation of MDA than PARG. Enhancement of peak currents is ascribed to the fast heterogeneous electron transfer kinetics that arise from the synergistic coupling between the excellent properties of PARG and semiconducting polymer, GQDs as high density of edge plane sites and subtle electronic characteristics and unique properties of CS such as excellent film-forming ability, high permeability, good adhesion, nontoxicity, cheapness, and a susceptibility to chemical modification. The prepared sensor showed 1 oxidation processes for MDA at potentials about 1V with a low limit of quantification 5.94nM. Finally, application of new sensor for determination of MDA in exhaled breath condensate was suited. In general, the simultaneous attachment of GQDs and CS to structure of poly amino acids provides new opportunities within the personal healthcare.

Covalent Modification of Glassy Carbon Surfaces by Electrochemical Grafting of Aryl Iodides.

The reduction of an aryl iodide is generally believed to involve a clean-cut two-electron reduction to produce an aryl anion and iodide. This is in contradiction to what is observed if a highly efficient grafting agent, such as an aryldiazonium salt, is employed. The difference in behavior is explained by the much more extreme potentials required for reducing an aryl iodide, which facilitates the further reduction of the aryl radical formed as an intermediate. However, in this study we disclose that electrografting of aryl iodides is indeed possible upon extended voltammetric cycling. This implies that even if the number of aryl radicals left unreduced at the electrode surface is exceedingly small, a functionalization of the surface may still be promoted. In fact, the grafting efficiency is found to increase during the grafting process, which may be explained by the inhibiting effect the growing film exerts on the competing reduction of the aryl radical. The slow buildup of the organic film results in a well-ordered structure as shown by the well-defined electrochemical response from a grafted film containing ferrocenylmethyl groups. Hence, the reduction of aryl iodides allows a precisely controlled, albeit slow, growth of thin organic films.

Poly arginine-graphene quantum dots as a biocompatible and non-toxic nanocomposite: Layer-by-layer electrochemical preparation, characterization and non-invasive malondialdehyde sensory application in exhaled breath condensate

This study reports on the electropolymerization of a low toxic and biocompatible polymer with entitle poly arginine-graphene quantum dots (PARG-GQDs) as a novel strategy for surface modification of glassy carbon (GC) surface and preparation a new interface for biomedical application. The fabrication of PARG-GQDs on GCE was performed using Layer-by-layer regime. Scanning electron microscopy (SEM) was confirmed dispersion of GQDs on the surface of PARG which lead to increase of surface coverage of PARG. The redox behavior of prepared sensor was then characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CHA), square wave voltammetry (SWV), linear sweep voltammetry (LSV). The electroactivity of PARG-GQDs coating towards detection and determination of malondialdehyde (MDA) as one of the most common biomarkers of oxidative stress, was then studied. Then, application of prepared sensor for the detection of MDA in exhaled breath condensate (EBC) is described. Electrochemical based sensor shows the lower limit of quantification (LLOQ) were 0.329nanomolar. This work is the first report on the integration of GQDs to poly amino acids. Further development can lead to monitoring of MDA or other exhaled breath biomarkers by GQDs functionalized poly amino acids in EBC using electrochemical methods.

Boron ion irradiation induced structural and surface modification of glassy carbon

The incorporation of boron into glassy carbon was achieved by irradiating two different types of targets: glassy carbon polymer precursor and carbonized glassy carbon. Targets were irradiated with a 45keV B3+ ion beam in the fluence range of 5×1015–5×1016ionscm−2. For both types of targets, the implanted boron was located in a narrow region under the surface. Following irradiation, the polymer was carbonized under the same condition as the glassy carbon samples (at 1273K) and examined by Raman spectroscopy, temperature programmed desorption, hardness and cyclic voltammetry measurements. Structural analysis showed that during the carbonization process of the irradiated polymers, boron is substitutionally incorporated into the glassy carbon structure, while for irradiated carbonized glassy carbon samples, boron irradiation caused an increase of the sp3 carbon fraction, which is most pronounced for the highest fluence irradiation. Further analyses showed that different nature of boron incorporation, and thus changed structural parameters, are crucial for obtaining glassy carbon samples with modified mechanical, chemical and electrochemical properties over a wide range.

One-step modification of carbon surfaces with ferrocene groups through a self-mediated oxidation of ferroceneacetate ions

This work describes a one-step method to modify covalently carbon surfaces with ferrocene moieties. The method is based on the oxidation of tetrabutylammonium ferroceneacetate in acetonitrile on glassy carbon electrodes. It is shown that covalent modification of glassy carbon surfaces is possible through a self-mediated electron transfer process. The first step of the mechanism consists in the oxidation of the ferrocene moiety to give rise to a transient ferroceniumacetate zwitterion, which, depending on the concentration, decomposes by either an intramolecular or an intermolecular electron transfer reaction where the carboxylate functional group is oxidized while the ferrocenium group is reduced. As a result of this reaction, carbon dioxide and ferrocenylmethyl radical are formed. In the forthcoming step, this radical reacts with the carbon surface, a reaction which is evidenced by the well behaved oxidation wave of adsorbed ferrocene in a solution containing only the solvent and the supporting electrolyte. Another interesting feature of the process is the fact that the ferrocene layer does not inhibit the electrode surface but this one acts as a surface redox catalyst of the oxidation and decarboxylation processes.

Surface Modification of GC and HOPG with Diazonium, Amine, Azide, and Olefin Derivatives

Surface modification of glassy carbon (GC) and highly oriented pyrolytic graphite (HOPG) was carried out with diazonium, amine, azide, and olefin derivatives bearing ferrocene as an electroactive moiety. Features of the modified surfaces were evaluated by surface concentrations of immobilized molecule, blocking effect of the modified surface against redox reaction, and surface observation using cyclic voltammetry and electrochemical scanning tunneling microscope (EC-STM). The measurement of surface concentrations of immobilized molecule revealed the following three aspects: (i) Diazonium and olefin derivatives could modify substrates with the dense-monolayer concentration. (ii) The surface concentration of immobilized amine derivative did not reach to the dense-monolayer concentration reflecting their low reactivity. (iii) The surface modification with the dense-monolayer concentration was also possible with azide derivative, but the modified surface contained some oligomers produced by the photoreaction of azides. Besides, the blocking effect against redox reaction was observed for GC modified with diazonium derivative and for HOPG modified with diazonium and azide derivatives, suggesting fabrication of a densely modified surface. Finally, the surface observation for HOPG modified with diazonium derivative by EC-STM showed a typical monolayer structure, in which the ferrocene moieties were packed densely at random. On the basis of those results, it was demonstrated that surface modification of carbon substrates with diazonium could afford a dense monolayer similar to the self-assembled monolayer (SAM) formation.

Covalent Modification of Glassy Carbon Surfaces by Using Electrochemical and Solid-Phase Synthetic Methodologies: Application to Bi- and Trifunctionalisation with Different Redox Centres

Glassy carbon electrodes functionalised with two redox centres have been prepared by using electrochemical and solid-phase synthetic methodologies. Initially the individual coupling of anthraquinone, nitrobenzene and dihydroxybenzene to a glassy carbon electrode bearing an ethylenediamine linker was optimised by using different coupling agents and conditions. Bifunctionalisation was then carried out, either simultaneously, with a mixture of nitrobenzene and dihydroxybenzene, or sequentially, with anthraquinone then nitrobenzene and with anthraquinone then dihydroxybenzene. Characterisation of these electrodes by cyclic voltammetry and differential pulse voltammetry clearly proved the attachment of the pairs of redox centres to the glassy carbon electrode. Their partial surface coverages can be controlled by varying the coupling agent or by controlling the substrate concentration during the solid-phase coupling process. Trifunctionalisation was also realised according to this methodology.

Spontaneous modification of glassy carbon surface with anthraquinone from the solutions of its diazonium derivative: An oxygen reduction study

The spontaneous grafting of anthraquinone (AQ) to glassy carbon (GC) from solutions of its diazonium derivative and the resulting electrocatalytic properties are reported. Surface modification was performed in acetonitrile and in aqueous solutions of various pH and a strong bonding of AQ to the surface is in evidence as the modified electrodes withstand long-term sonication in acetonitrile. The dependence of AQ coverage on immersion time was studied by cyclic voltammetry. The attached AQ showed a quasi-reversible redox-behaviour in 0.1 M KOH. The electrocatalytic properties of these electrodes and the corresponding kinetic parameters for oxygen reduction were determined using rotating disk electrode (RDE) voltammetry and the results were analysed using a surface redox catalytic cycle model for quinone modified electrodes. O 2 reduction reaction parameters were compared with those obtained with electrochemically grafted electrodes. It is concluded that the two grafting methods give similar results and in particular, the rate constant of the reaction between the semiquinone and molecular oxygen was very close for electrografted to spontaneously modified electrodes. The different possible heterogeneous reaction mechanisms are discussed by comparison with dediazoniation reactions in solution and the involvement of the Gomberg–Bachmann dediazoniation mechanism in the generation of aryl radical for surface functionalisation is proposed.

Covalent modification of glassy carbon surface with organic redox probes through diamine linkers using electrochemical and solid-phase synthesis methodologies

Various mono-Boc-protected diamines have been covalently grafted to glassy carbon electrodes by electrochemical oxidation of the free amine. After deprotection of the Boc group, anthraquinone and nitrobenzene probes were coupled to the linkers using solid-phase coupling reactions. X-Ray photoelectron spectroscopy and cyclic voltammetry were used to monitor the coupling efficiency, effect of linker length on the surface coverage and electron transfer between the attached redox probes and electrode. The anthraquinone surface coverage was found to decrease as the chain length of alkyl diamine linker increased and the electron transfer kinetics were found to be faster for the lower coverages and the longer, more flexible linkers. In the case of nitrobenzene, there was only a slightly change in coverage with increasing linker length. This electrochemical attachment of protected diamine linkers followed by solid-phase coupling provides a very versatile methodology for attaching a wide range of molecular architectures onto glassy carbon surfaces.

Modification of Glassy Carbon Surfaces by Atmospheric Pressure Cold Plasma Torch

The effect of plasma treatment on glassy carbon (GC) surfaces was studied with adhesion improvement in mind. A newly constructed remote plasma source was used to treat GC plates. Pure He and a dilute NH3/He mixture were used as feed gases. Optical emission spectroscopy was performed for plasma torch diagnostics. The treatment resulted in surface etching, substantially enhanced by NH3, as well as a roughening of the surface as measured by atomic force microscopy. Furthermore, the treated area showed an increased wettability indicating the addition of polar functional groups to the surface. X-ray photoelectron spectroscopy confirmed the introduction of several oxygen and nitrogen containing surface functional groups. The adhesion to epoxy was dramatically improved after exposure to either plasma, the effect being largest when NH3 was present in the feed gas.

Surface Modification of Glassy Carbon by Pulsed Laser Irradiation with Several Wavelengths

Glassy carbon is one of several types of amorphous carbon and has a complicated network structure made up of multilayers consisting of sp2 hybridized carbon. We briefly reported the phenomenon of the hardening of glassy carbon induced by KrF excimer laser (λ=248 nm) irradiation. In this study, ArF, KrF, XeCl, fundamental generation and 2nd harmonic generation waves of Nd:YAG lasers were applied on the glassy carbon target directly under the atmospheric pressure of argon to confirm the appropriate conditions for the hardening of glassy carbon. Surface hardening was observed with variations of the surface morphology and the structure of the modified layer.

Effects of Plasma Composition Elements on the Surface Modification of Carbon Materials by Nitrogen Plasma.

This investigation was conducted on the surface modification of Glassy carbon(GC) material by R.F. glow discharge plasmas with the aim of investigating the surface nitriding for the GC materials with the nitrogen plasma. The contact angles for water to GC surface after the plasma treatment was measured. And their surfaces were analyzed by using Raman spectroscopy and ESCA. Nitrogen-plasma treatment makes the GC surface hydrophilic. The difference Δθ of the contact angles between those before the treatment (80°) and those at 30minutes after the treatment was investigated. Δθ is considered the effects of plasma treatment. As input power increased from 10W to 70W, the difference Δθ increased (on power electrode : from 46° to 63°, on earth electrode: from 32° to 58°). The composition ratios, O/C and N/C on the untreated GC surfaces were 0.0 and 0.0, respectively. Upon treatment with N2 plasma, this ratio increased to 0.12(O/C) and 0.18(N/C) for the GC surface. Nitrogen atoms and oxygen atoms, namely, were introduced to the GC surface. Introduction of nitrogen atoms was caused by the nitrogen radicals and nitrogen ions. The oxygen atoms were introduced by nitrogen ions. Nitrogen ions were accelerated by the sheath voltage and bombarded the GC surface at high energy. As the result, the active and long life-time radicals were generated. The reaction between these radicals and the oxygen in the air took place when they were taken out from the treatment chamber to the air after plasma treatment.The contact angle decreased by introducing the functional groups having nitrogen atoms and oxygen atoms onto the GC surface with nitrogen plasma. The surface nitriding of the carbon materials can be made easily with the short-time treatment of nitrogen plasma.