Electrocatalytic Oxidation Of Ascorbic Acid Research Articles

Reduced Graphene Oxide Decorated Titanium Nitride Nanorod Array Electrodes for Electrochemical Applications

This work describes the fabrication and characterization of a new high surface area nanocomposite electrode containing reduced graphene oxide (rGO) and titanium nitride (TiN) for electrochemical applications. This approach involves electrochemically depositing rGO on a high surface area TiN nanorod array electrode to form a new nanocomposite electrode. The TiN nanorod array was first formed by the glancing angle deposition technique in a DC (Direct Current) sputtering system. GO flakes of ~1.5 μm in diameter, as confirmed by Dynamic Light Scattering (DLS), were electrodeposited on the nanostructured TiN electrode via the application of a fixed potential for one hour. The surface morphology of the as-prepared rGO/TiN electrode was evaluated by scanning electron microscopy (SEM) and the presence of rGO on TiN was confirmed by Raman Microscopy. The CV shows an increase in the capacitive current at rGO/TiN as compared to TiN. The rGO decorated TiN electrode was then used for analyzing the electrocatalytic oxidation of ascorbic acid and dopamine, and the reduction of nitrate by CV and linear sweep voltammetry (LSV), respectively. CV or LSV show that the electrochemical kinetics of these three analytes are significantly faster on rGO/TiN than TiN itself. Overall, the rGO/TiN electrode showed better electrochemical behavior for biomolecules like ascorbic acid and dopamine as well as another target analyte, nitrate ions, compared to TiN by itself.

Modification of Glassy Carbon Electrodes with Complexes of Manganese(II) with Some Phenanthroline Derivatives Immobilized in Nafion Layer.

Manganese(II) complexes with phenanthroline derivatives modified with different substituents were synthesized and incorporated into Nafion layers covering the surfaces of glassy carbon electrodes and were studied electrochemically. Formal potentials and apparent diffusion coefficients were calculated and discussed. The suitability for electrocatalytic oxidation of ascorbic acid and glycolic acid was examined. The surfaces of modified electrodes were characterized using atomic force microscopy.

Green synthesis of silver nanoparticles using Salvia fruticosa Mill. extract and the effect of synthesis parameters on their formation, antioxidant, and electro-catalytic activity

Among green synthesis methods, which are an eco-friendly, non-toxic, simple, and safe approach for the synthesis of silver nanoparticles (AgNPs), using plant extract is the most efficient method. Salvia fruticosa Mill. which was not used formerly was selected for this research. By changing the synthesis parameters (the amount of extract, extract concentration, and silver ion concentration in precursors), their effects on the formation and structure of nanoparticles were investigated by UV-visible spectroscopy, transmission electron microscopy and Fourier transform infrared spectroscopy techniques. The antioxidant activity of extracts and AgNPs was evaluated by performing DPPH assay. It is observed that the phytosynthesized nanoparticles also possess antioxidant potentials. Finally, AgNPs were used as modifiers for carbon paste electrode (CPE) and their effect on charge transfer resistance and the ascorbic acid signal was investigated by using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and square wave voltammetry (SWV). E1-1/CPE showed good electro-catalytic oxidation of ascorbic acid and can be utilized for the development of the new sensors. According to results, in the process of green synthesis of AgNPs, synthesis parameters are vital as they change not only the size and size distribution of the AgNPs but also their antioxidant activity and electrochemical properties.

Sea-urchin-structured NiCo2O4 decorated nitrogen-doped graphene for enhanced electrochemical detection of ascorbic acid

Developing high-performance electro-catalyst for detection of ascorbic acid is greatly desirable. A convenient and cost-effective route for the synthesis of sea-urchin-structured NiCo2O4 decorated nitrogen-doped graphene was demonstrated. The morphology, composition, and electrochemical properties of the obtained products were characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and cyclic voltammetry. The electrocatalytic behaviors of sea-urchin-structured NiCo2O4 decorated nitrogen-doped graphene-modified glass carbon electrodes were investigated by cyclic voltammetry and chronoamperometry. The as-prepared electrode exhibited distinguished electrocatalytic oxidation of ascorbic acid. The linear response relationship for ascorbic acid was obtained ranging from 2.0 μM to 6 mM with a rapid response time of less than 2 s and a low detection of the limit of 0.39 μM (signal/noise = 3), which could be attributed to the high conductivity, high electroactivity for electrocatalytic oxidation of ascorbic acid, as well as high specific surface area of sea-urchin-structured NiCo2O4 decorated nitrogen-doped graphene. In addition, the modified electrode showed good anti-interference ability, long-term stability, and high reproducibility. The excellent electrocatalytic behavior of sea-urchin-structured NiCo2O4 decorated nitrogen-doped graphene may make it promising for applications in electrochemical analysis.

Electrocatalytic oxidation of ascorbic acid in the basic medium over electrochemically functionalized glassy carbon surface

In a mild acidic medium (0.10 M H2SO4), a pristine glassy carbon electrode (GCE) has been electrochemically activated via electrochemical oxidation which has been used for efficient ascorbic acid (AA) direct oxidation. An oxidized GCE exhibits a well-defined redox pair in 0.10 M H2SO4 due to development of functional groups (C=O) on the surface of the GCE during the electrochemical oxidation process. Electrochemical and X-ray photoelectron spectroscopy (XPS) have been employed to characterize the GCE surface before and after functionalization. The resultant electrode surface was employed to execute electrochemical oxidation of ascorbic acid molecules in an alkaline medium. The voltametric measurements of AA oxidation at the oxidized GCE showed that the oxidized GCE exhibited better electrochemical performance in 0.10 M NaOH compared to the pristine GCE. It was observed that oxidation of AA followed 1st order and diffusion-controlled kinetics on the oxidized GCE surface. The hydrodynamic voltammogram analysis confirmed that oxidation of AA proceeds via a 2e− transfer pathway and followed a stepwise mechanism. It was found that, for the oxidation of AA, the standard rate constant (ko) has a value 4.47 × 10−3 cm s−1 with a Eo value of −0.29 V vs Ag/AgCl (sat. KCl). The proposed oxidized GCE successfully decreases AA oxidation overpotentials, which enhances the possibility of using it as an anode in ascorbic acid (AA) fuel cells.

Metal-directed two new Anderson-type polyoxometalate-based metal–organic complexes with different electrocatalytic sensing performance

Two new Anderson-type polyoxometalate (POM)-based metal–organic complexes, namely: H[Cd(L)(CrMo6(OH)6O18)]·2H2O (1) and H[Co(L)(CrMo6(OH)6O18)(H2O)2]·3H2O (2) (L = N, N'-bis(3-pyridinecarboxamide)-1,4 cyclohexane) have been successfully synthesized under hydrothermal condition and characterized in detail. For 1, the [CrMo6(OH)6O18]3- anion adopts hexadentate coordination pattern connecting with binuclear Cd2II unit to form a two-dimensional (2D) layer, which is further expanded into a three-dimensional framework by the L ligands. In 2, The CrMo6 anions exhibit tetradentate coordination mode to connect the metal ions constructing a 2D layer. The L ligand does not play a linkage role and only suspend on the 2D network, which is different from complex 1. The influence of central metal ions on the architectures was discussed. The electrocatalytic reduction of potassium bromate and the electrocatalytic oxidation of ascorbic acid by complexes 1 and 2 were investigated. These title complexes could be regarded as amperometric sensors for the detection of potassium bromate and ascorbic acid. In particular, complex 1 shows the lowest detection limit for these two substances, suggesting its better electrochemical performance.

Fabrication of IrOx immobilized glassy carbon surface for attaining electrocatalytic ascorbic acid oxidation reactions

The development of an efficient electrocatalyst for the direct oxidation of ascorbic acid (AA) has gained considerable interest since AA may be applied as an environment-friendly alternative renewable biofuel in fuel cells. In the present work, the electrocatalytic oxidation of AA was implemented at IrOx immobilized glassy carbon electrode (GC-IrOx) in an acidic medium. Prior to use, the physical properties of GC-IrOx surface were investigated by means of scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). The XPS analysis revealed that a film of IrOx formed on the GC surface while it was cycled between 0 and 1.0 V vs Ag/AgCl (sat. KCl) reference electrode in Ir2O3 colloidal solution. The voltammetric investigations of AA oxidation at the GC-IrOx electrode revealed 4-folds higher current compared to a pristine GC electrode suggesting an excellent electrocatalytic performance. The Ir(III)/Ir(IV) redox couple is assigned for catalyzing the reaction. It was found that AA oxidation followed first order kinetics on the GC-IrOx electrode surface. The heterogeneous electron transfer (ET) kinetic study unveiled that AA oxidation reaction followed stepwise mechanism at potentials below 0.38 V and concerted mechanism above this potential with respect to a Ag/AgCl (sat. KCl) reference electrode. In this study, the standard rate constant (ko) pertaining to AA oxidation was evaluated as 7.25 × 10−4 cm s − 1. The GC-IrOx electrode exhibited reasonably excellent stability, which mounts the probability of its application as an anode in the AA fuel cells.

Recycling of graphite and metals from spent Li-ion batteries aiming the production of graphene/CoO-based electrochemical sensors

This work describes the synthesis of hybrid materials based on reduced graphene oxide (rGO) and cobalt oxide (CoO) from recycled Li-ion batteries. A hydrometallurgical route was employed in the recycling process, with citric acid and nitric acid used as the leaching agents for the cathode and anode materials, respectively. Graphene oxide (GO) was prepared from the recycled graphite by a modified Hummers method; the hybrid material was produced by mixing GO and the recycled metal oxides (mostly CoO) using a sol-gel route followed by heat treatment at 450 °C during 2 h. The physicochemical characterization of the hybrid material was conducted by X-ray diffraction, scanning electron microscopy and solid-state 7Li and 13C nuclear magnetic resonance (NMR) spectroscopy; the results indicated the formation of crystalline CoO (with face centered cubic structure) and rGO (with turbostratic structure), whereas lithium and manganese were also identified as minor components. The performance of this product as electrochemical sensor was evaluated by cyclic voltammetry. The study of the electrocatalytic oxidation of ascorbic acid using the hybrid material as electrode showed good linearity in the relationship between the oxidation current and the acid concentration. These results showed that the hybrid material produced from the recycled batteries is promising for applications as an enzyme-free electrochemical sensor.

A Keggin-Type Tungstovanadate-Based Hybrid Compound: Synthesis, Crystal Structure, and Electrocatalytic Oxidation of Ascorbic Acid

A new V-centered Keggin polyoxometalate-based inorganic-organic hybrid (HPpz)3[VW12O40] (I) (Ppz = piperazine) has been hydrothermal synthesized and characterized by IR spectroscopy, UV−Vis spectroscopy, elemental analysis and single-crystal X-ray diffraction (CIF file CCDC no. 1835683). Compound I belongs to the rhombohedral space group $$R\bar {3}c$$ and displays a three-dimensional supramolecular structure. The band gap energy value calculated for compound I was observed to be 1.30 eV using UV−Vis-NIR absorption spectrum. Furthermore, electrocatalytic performance of I has also been investigated in details.

Electrochemistry of redox probes at thin films of carbon nano-onions produced by thermal annealing of nanodiamonds

Electrochemical data for pristine carbon nano-onions (CNO), radio frequency Ar/O2 plasma oxidized CNO (CNO-RF) and chemically oxidized CNO (CNO-OXI) cast on glassy carbon electrodes (GCE) are presented. The electrochemical response was evaluated by cyclic voltammetry using [Fe(CN)6]3-, [Ru(NH3)6]3+, [Fe(H2O)6]2+ and ferrocenemethanol (FcCH2OH) as redox probes. The electron transfer kinetics for these probes was influenced by the nature of functional groups on the electrode material, adsorption processes and the electrostatic interactions between the redox probes and the surface of the different carbon nano-onions. The electrocatalytic properties for the reduction of O2 to H2O2 at CNO, CNO-RF and CNO-OXI modified electrodes were also evaluated using linear sweep voltammetry. The electroreduction of O2 shifted to more positive potential (up to −0.16 V vs Ag/AgCl) as the oxidation degree of CNO increased. In the same way, the sensitivity for the electrochemical detection of H2O2 was enhanced up to 50-fold respect to unmodified GC electrode. Furthermore, the electrocatalytic oxidation of ascorbic acid (AA), dopamine (DA) and uric acid (UA) was studied by cyclic voltammetry and differential pulse voltammetry at CNO, CNO-RF and CNO-OXI modified electrodes. The electrodes displayed excellent electrocatalytic activity for the oxidation of AA, DA and UA. These results demonstrate that CNO enhance the electroactive properties of redox probes and are thus promising materials for electrochemical detection and metal-free electrocatalysts of different reactions. Additionally, the electrochemical data obtained here can serve to understand the performance of carbon nano-onion thin films as electrode materials.

Tuning Poly(ionic liquid) as a Facile Anion (Hexacyanoferrate(III) ion) Exchanger after Being Adsorbed on Graphitic Nanomaterial and Its Versatile Electrocatalytic Oxidation of Ascorbic Acid

Owing to their conductivity and high polarity, ionic liquids and poly(ionic liquids) (PILs) have been often used as an electrolyte for various applications in electrochemistry. Due to the unfavorable ion-exchange property and structural feature (hydrophobic environment and inaccessible ionic site), unmodified ILs and PILs are rarely worked out as an ion-exchanging system. Herein, we show elegant tuning of aromatic unit bearing PILs as an efficient anionic ion exchanger after being combined with graphite nanomaterials like graphite nanopowder (GNP) and carbon nanotube for novel electrocatalytic applications. A chemically modified electrode prepared out of GNP and random copolymer of 1-vinyl-3-pentylimidazolium chloride and styrene (coPIL₁Cl) composite ethanol suspension on a glassy carbon electrode (GCE) showed facile immobilization of hexacyanoferrate(III) ion (as a model anionic system), electrode designated as GCE/GNP-coPIL₁@Fe(CN)₆³–, in pH 7 phosphate buffer solution. The modified electrode yielded well-defined surface-confined redox peak at equilibrium potential, E₁/₂ = 100 ± 5 mV vs Ag/AgCl with a surface excess and relative standard deviation values of 3.0 nmol cm–² and 1.8%, respectively. From the experiments with different functional counterions (Cl–, SO₃CF₃–, BF₄–, and PF₆–), alkyl chains (butyl and pentyl groups), and N-terminal-substituted aromatic unit and from physicochemical characterizations of PIL-modified electrodes, how the π–π interaction, hydrophobic and hydrophilic sites, and steric factor of PIL influence the ion-exchanging behavior of the GNP-coPIL₁Cl composite with ferricyanide ion was demonstrated. Electrocatalytic oxidation of ascorbic acid (AA) was investigated as a model system for the ferricyanide-modified electrode performance using cyclic voltammetric and amperometric i–t techniques. Highly selective and superior electrocatalytic and sensing of AA over its unmodified electrodes were noted.

Voltammetric determination of ascorbic acid with zinc oxide modified glassy carbon electrode

Zinc oxide (ZnO) nanostructures electrodeposited from aqueous zinc nitrate solution at 70 °C onto glassy carbon electrode (GCE) were used as electrochemical detectors. The morphology, structure, chemical composition and conductivity of the as-deposited layers were determined using scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray analysis and UV–Vis spectroscopy. A highly oriented crystalline ZnO deposit made of a dense array of randomly oriented hexagonal nanorods was obtained without any additives in solution. The electrocatalytic oxidation of ascorbic acid (AA) was studied using cyclic voltammetry in 0.1 M phosphate buffer solution at pH 6.8. Comparing the response for AA oxidation on the bare and modified electrodes, the peak potential was shifted to − 0.45 V on ZnO/GCE with higher current densities and transfer coefficient, due to a simultaneous increase in oxidation rate and surface area. A linear relationship was determined between the anodic peak current and the AA concentration in the range of 0.1–5 mM.

Poly(amido amine) dendrimer and silver nanoparticle–multi-walled carbon nanotubes composite with poly(neutral red)-modified electrode for the determination of ascorbic acid

A new film containing poly(amido amine) dendrimer, silver nanoparticles and multi-walled carbon nanotubes composite with poly(neutral red) was prepared on a paraffin wax impregnated graphite electrode. The PAMAM / AgNPs–MWCNT / PNR film exhibited promising electrocatalytic oxidation of ascorbic acid (AA) in acetate buffer solution of pH 4.0. The PAMAM / AgNPs–MWCNT / PNR film-modified electrode enhanced the sensitivity of detection of AA. The PAMAM / AgNPs–MWCNT / PNR film-modified electrode was characterized by cyclic voltammetry, chronoamperometry, hydrodynamic voltammetry (HDV) and difference pulse voltammetry. These experiments confirmed the electrocatalytic oxidation of AA by PAMAM / AgNPs–MWCNT / PNR film-modified electrode. The PAMAM / AgNPs–MWCNT / PNR-modified electrode has been found to possess good electrocatalytic activity towards AA oxidation which has been observed at a lower oxidation potential of around 0.26 V with a higher current response. The electrochemical oxidation of AA by PAMAM / AgNPs–MWCNT / PNR-modified electrode involved a two proton and two electron process. A linear relationship between the catalytic current and AA concentration was obtained in the range from 0.16 to 2500 \(\upmu \)M with a detection limit of 0.053 \(\upmu \)M.

Electrochemical Diagnosis of Chemical Switch: Impact of Structural Changes on Charge Transport Mechanism of “Redox Anion Bound Polysilsesquioxane” Film

AbstractHerein, we report the structurally dependent charge transport mechanism of ferrocyanide ions immobilized in a protonated amine functionalized polysilsesquioxane (PSQ) film (Redox polymer film). This redox polymer film shows anion actuated reversible “active to inactive” electrochemical interfaces when the electrolyte anion is changed from chloride to perchlorate as a result of swelling and hydrophobic collapse of the PSQ film, respectively. This concept was successfully applied for switchable electrocatalytic oxidation of ascorbic acid by a [Fe(CN)6]4−‐PSQ film. In addition, it was shown in cyclic voltammetric (CV) studies that the presence of HPO42− and CO32− is leading to strong irreversible structural collapse of the PSQ film, whereas, the presence of SO42− and S2O82− is leading to reversible structural changes of the PSQ film within chloride ion medium. Reversible structural transition between swelling and aggregation (voltammetric response reversibly changing from peak to sigmoidal shape) described in this work is new and provides mechanistic insight into redox polymer electrochemistry and allows differentiating electron hopping from physical motion of redox polymers. Moreover, ion‐exchange between bound redox anions and divalent anions in the electrolyte at fixed positive surface sites of PSQ film was explained in terms of Jones‐Dole B‐coefficient. Electrochemical impedance spectroscopy, Atomic force microscopy, Contact angle measurement and UV‐visible spectroscopy analysis of above phenomenon were consistent with CV results.

Aniline‐nonamer segmented polyurea: A facile electrocatalyst for detection of ascorbic acid

ABSTRACTAn unprecedented A‐B‐A type block copolymer electroactive polyurea (EPU) is designed and synthesized with tetraaniline dimer and 1,4‐phenylenediamine via an oxidative coupling, where aniline–nonamer and hexamethylene di‐urea constitute two segments. The EPU was characterized by spectral techniques such as Fourier transform infrared spectroscopy, nuclear magnetic resonance, and UV–vis spectra. The structural characterization of the prepared EPU was obtained by powder X‐ray diffraction and X‐ray photoelectron spectroscopy techniques. EPU reorganizes into core–shell microcapsules in presence of aqueous acetic acid/n‐octane interface. These microcapsules exhibited a wide range of pH responses in their absorption spectrum (UV–vis). The EPU is modified as carbon paste electrode which exhibits a remarkable electrocatalytic oxidation of ascorbic acid (AA, Vitamin C) in 0.2 M and pH 7.0 phosphate buffer solution. The carbon paste electrode is useful in sensing as low as 50 µM of ascorbic acid. This can open up new opportunities for fast, simple detection of AA providing a promising platform for sensor/biosensor designs for AA detection. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46630.

A Dense Manganese Porphyrin-Nanobar Random Arrays: Direct and Electrocatalytic Oxidation of Ascorbic Acid in the Presence of Dopamine and Uric Acid

An array of micro/nanoelectrodes offers most of the advantages of single micro/nanoelectrodes, but with the added benefit of a higher total current output and increasing sensitivity. This work reports the analytical performance of a gold electrode modified with a Mn(III) porphyrin nanobar-film (NBMn-PPh) employed for the sensitive determination of Ascorbic Acid (AA) at pH = 7.4 in the presence of always coexistence interferences Dopamine (DA) and Uric Acid (UA).

Fullerene-doped polyaniline as new redox nanoprobe and catalyst in electrochemical aptasensor for ultrasensitive detection of Mycobacterium tuberculosis MPT64 antigen in human serum.

Tuberculosis caused by Mycobacterium tuberculosis (MTB) is still a major threat to global public health. However, the existing methods for MTB detection are usually complicated and time consuming with unsatisfactory sensitivity and specificity. In this work, a relatively simple and ultrasensitive electrochemical aptasensor based on novel signal generation and amplification was constructed for the determination of MTB antigen MPT64. The coil-like fullerene (C60)-doped polyaniline (C60-PAn) nanohybrids with large surface area, abundant active groups and excellent electric performance were synthesized and used both as new redox nanoprobe and catalyst for the generation and amplification of electrochemical signal for the first time. Then gold nanoparticles decorated C60-PAn nanocomposites (GNPs-C60-PAn) were labeled with signal aptamer to form the tracer label. After the sandwich reaction of target MPT64 antigen between capture aptamer and the tracer label, a distinguishing detection signal of C60-PAn would be observed. Moreover, the detection signal could be enormously enhanced towards the efficient electrocatalytic oxidation of ascorbic acid based on C60-PAn, resulting in further improvement of the sensitivity. With the excellent redox and electrocatalytic activity of C60-PAn, a wide detection linear range from 0.02 to 1000pg/mL was obtained with a detection limit of 20fg/mL for MPT64. The proposed aptasensor showed high selectivity to target antigen compared with possible interfering substances. More importantly, it also exhibited excellent specificity and sensitivity for MPT64 detection in serum samples of tuberculosis patients, which provided a rapid and efficient detection method for MTB infection.

Facile construction of AuNP modulated SDS-wrapped G-TC-tailored electrode for sensitive detection of ascorbic acid

AuNP modulated SDS wrapped G-TC electrode was fabricated for electrocatalytic oxidation of ascorbic acid with high sensitivity of 4017.0 μA mM−1. The LOD was calculated to be 0.07 μM and the sensor was investigated for determination of AcA in real sample (Vit. C tablets) with satisfactory results.

Highly sensitive and efficient voltammetric determination of ascorbic acid in food and pharmaceutical samples from aqueous solutions based on nanostructure carbon paste electrode as a sensor

A square wave voltammetric method for the trace analysis of ascorbic acid was developed in this study. Carbon paste electrode was modified with NiO nanoparticle and 1-butyl-3-methylimidazolium tetrafluoroborate as a binder. Electro-oxidation behavior of ascorbic acid on the modified electrode was studied, which indicated that the nanostructure modified electrode could efficiently promote electrocatalytic oxidation of ascorbic acid. A fast, selective, high sensitive and simple electrochemical strategy was then developed for trace analysis of ascorbic acid using the constructed electrode. The catalytic oxidation signal exhibited a wide linear range from 0.08 to 380.0μM toward the concentration of ascorbic acid with a sensitivity of 0.0158μA/μM, and the limit of detection was as low as 0.04μM. The suggested sensor was also used for quantitative determination of ascorbic acid in food and pharmaceutical samples.

Research on the self-assembly of exfoliated perovskite nanosheets (LaNb2O7−) and cobalt porphyrin utilized for the electrocatalytic oxidation of ascorbic acid

A sandwich-structured nanocomposite of LaNb2O7/CoTMPyP was fabricated via electrostatic interactions between LaNb2O7− nanosheets and cobalt porphyrin cations, and the obtained hybrid film exhibited excellent electrocatalytic activities toward AA.