Formal Potential Values Research Articles

Intramolecular Hydrogen Bonding Effect on the Electron-Transfer Thermodynamics of a Series of o-Nitrobenzyl Alcohol Derivatives.

From thermoelectrochemical experiments and electronic structure calculations of a series of nitrobenzyl alcohol derivatives, the effect of intramolecular hydrogen bonding (IHB) on the electron transfer thermodynamics is discussed on a molecular basis. A linear correlation between formal reduction potential (E1/2) values and temperature was obtained for the temperature range from 300 to 350 K. Estimated electron transfer entropy values (ΔS)─determined from this dependence─and the enthalpy (ΔΔH) changes relative to o-nitrobenzyl alcohol confirmed that the effect of the formation of IHB proved to be decisive in the charge-transfer thermodynamics. The possibility of intermolecular hydrogen bonding is further discussed upon comparing thermodynamic data among three different solvents.

Quantum Dot-Sensitised Estrogen Receptor-α-Based Biosensor for 17β-Estradiol

17β-estradiol (E2) is an important natural female hormone that is also classified as an estrogenic endocrine-disrupting compound (e-EDC). It is, however, known to cause more damaging health effects compared to other e-EDCs. Environmental water systems are commonly contaminated with E2 that originates from domestic effluents. The determination of the level of E2 is thus very crucial in both wastewater treatment and in the aspect of environmental pollution management. In this work, an inherent and strong affinity of the estrogen receptor-α (ER-α) for E2 was used as a basis for the development of a biosensor that was highly selective towards E2 determination. A gold disk electrode (AuE) was functionalised with a 3-mercaptopropionic acid-capped tin selenide (SnSe-3MPA) quantum dot to produce a SnSe-3MPA/AuE electroactive sensor platform. The ER-α-based biosensor (ER-α/SnSe-3MPA/AuE) for E2 was produced by the amide chemistry of carboxyl functional groups of SnSe-3MPA quantum dots and the primary amines of ER-α. The ER-α/SnSe-3MPA/AuE receptor-based biosensor exhibited a formal potential (E0') value of 217 ± 12 mV, assigned as the redox potential for monitoring the E2 response using square-wave voltammetry (SWV). The response parameters of the receptor-based biosensor for E2 include a dynamic linear range (DLR) value of 1.0-8.0 nM (R2 = 0.99), a limit of detection (LOD) value of 1.69 nM (S/N = 3), and a sensitivity of 0.04 µA/nM. The biosensor exhibited high selectivity for E2 and good recoveries for E2 determination in milk samples.

Interaction of Polyhedral Oligomeric Silsesquioxanes (POSS) Modified with a Metallocyano Complex and Their Application Use as Sensor for the Detection of Isoniazid

We prepared herein polyhedral oligomeric silsesquioxanes (POSS) modified with zinc and ferrocyanide to create an electroactive nanohybrid material (SZnH) that was then characterized using spectroscopic techniques like FTIR, XPS, SEM, EDX,TEM and CV. Cyclic voltammograms of the SZnH-modified graphite paste electrode (GPSZn) revealed three redox processes with formal potential (Eo’) values of 0.33 (I), 0.78 (II) and 1.01 ± 0.01 (III) V (vs Ag/AgCl). The second redox process (II) indicated high current intensities and were used to identify isoniazid in electroanalytical tests. GPSZn was highly sensitive to isoniazid concentrations, presenting two linear response at concentration ranges from 1.0 × 10−5 to 1.0 × 10−3 mol l−1, with the lowest limit of detection (LOD) of 3.70 × 10−6 mol l−1. The material appears to be an excellent candidate for use in developing and applying electrochemical sensors in the detection of isoniazid.

Electrocatalytic oxidation of ammonia in the neutral medium using Cu2O.CuO film immobilized on glassy carbon surface

Enhanced catalytic response towards ammonia oxidation was observed at Cu 2 O.CuO-GCE electrode. Ammonia undergoes 3 electron transfer reaction to produce N 2 as the end product. The first electron transfer was evaluated to be the rate determining step, therefore, the reaction intermediates (NH 2 ads , NH ads , N ads ) doesn’t control the rate of reaction. • Sustaining the stability of the electrode is the main challenge in electrochemical oxidation of NH 3. • We discuss the role of mixed Copper oxides (CuO-Cu 2 O) on Glassy Carbon electrode for NH 3 oxidation. • The modified electrode shows good catalytic stability with increasing NH 3 concentration. • Neutral medium is found to be most favorable for NH 3 oxidation at CuO-Cu 2 O-GCE electrode. Electrocatalytic ammonia oxidation reaction (AOR) was executed on the copper oxide layer, electrochemically deposited on a glassy carbon electrode (GCE) surface. The XPS analysis revealed that the oxide film contains 80% Cu(I) and 20% Cu(II) species. The EIS analysis suggests that the resultant surface can catalyze ammonia oxidation reactions efficiently. The as prepared GCE-Cu 2 O.CuO favored the neutral medium for executing AOR with a degradation rate of 3.76 × 10 −4 mol min −1 cm −2 . Kinetic investigation shows that ammonia oxidation involves a three electron transfer first-order reaction. Tafel analysis of current–potential polarization curves indicates that species such as NH 3 or NH ads and NH 2ads intermediates do not influence the reaction rate, which made the electrode unique for carrying out AOR. The formal potential value of AOR was evaluated to be ~0.7 V vs Ag/AgCl (sat.KCl) having standard rate constant ( k° ) of 5.52 × 10 −6 cm/s.

Novel Tl(III) complexes containing pyridine-2,6-dicarboxylate derivatives with selective anticancer activity through inducing mitochondria-mediated apoptosis in A375 cells

Three novel Tl(III) complexes (C1), (C2) and (C3) were synthesized using the one-pot reactions of pyridine dicarboxylic acid derivatives, 2-aminobenzimidazole and/or 4-aminopyridine, and also thallium(III) nitrate trihydrate metal salt. The structure of all three complexes was determined by the single-crystal X-ray diffraction. C1 and C2 were realized to be isostructural with disordered square anti-prismatic geometry and for C3 arrangement of the distorted tricapped triangular prism was proposed. Cyclic voltammetry measurements on the complexes exhibited that formal potential values are more positive for C1 (E0ˊ 0.109 V) and C3 (E0ˊ 0.244 V) compared to C2 (E0ˊ –0.051 V), versus Ag/AgCl under argon. Moreover, cytotoxicity of the compounds was evaluated in vitro against two cancer cell lines including a human melanoma (A375), a human colon adenocarcinoma (HT29), and also one normal cell human foreskin fibroblast (HFF). The selective and potent cytotoxicity effect was exhibited by C1 and C3 on cancer cell lines. The apoptosis through a caspase-dependent mitochondrion pathway was confirmed by ROS production, MMP reduction, p53 activation, Bax up-regulation, and Bcl-2 down-regulation, cytochrome c release, procaspase-9, and 3 expression, for A375 cells treated to C1 and C3. According to similar cellular uptake of the complexes in A375 cell line, the generation of ROS was considered as an effective agent to justify the inhibition effect C1 and C3 on mentioned cells. Furthermore, arresting the cell cycle in the G2-M phase and inducing apoptosis were indicated by these two complexes.

A Comparative Voltammetric Study of a Chemically Modified Octa(3-Aminopropyl)Octasilsesquioxane and DAB-AM-16 Dendrimer Supported on the Silica Gel Surface for Dipyrone Detection

Octa(3-aminopropyl)octasilsesquioxane and DAB-AM-16 dendrimer, due to their specific chemical and physical properties, give wide application in various fields of science. Because they have a large number of NH2 reactive groups at their ends, they are capable of interacting with different substances, generating in this way different compounds with enormous analytical potential that can be used in the electrocatalytic determinations and oxidations of some substances of environmental and biological interest. In this work, after a rigorous voltammetric study, the electroanalytical potentiality of the chemically Ni2+ metal ions chealed silica gel surface modified with octa(3-aminopropyl)octasilsesquioxane and DAB-AM-16 dendrimer was tested for dipyrone detection. The cyclic voltammogram of the graphite paste electrode, with both materials (20% w/w) showed two redox process. The following formal potential (Eθ′) values for both materials were identical: (Eθ′)I = 0,26 V; (Eθ′)II = 0,51 V vs Ag/AgCl (KCl = 1.0 mol L−1; v = 20 mV s−1). For dipyrone detection assay, the limite of detection were of 9.17 × 10−5 mol L−1 with an amperometric sensitivity of 15.78 mA / mol L−1 with a relative standard deviation of ±3% (n = 3) and of 4.79 × 10−4 mol L−1 with an amperometric sensitivity of 11.10 mA / mol L−1 with a relative standard deviation of ±2% (n = 3) respectively for silica gel surface modified with octa(3-aminopropyl)octasilsesquioxane and DAB-AM-16 dendrimer.

Mercaptoalkanoic Acid‐Induced Band Gap Attenuation of Copper Selenide Quantum Dot

AbstractCopper selenide quantum dot (CuSeQD) materials functionalised with mercaptoalkanoic acids {3‐mercaptopropionic acid (3‐MPA), 6‐mercaptohexanoic acid (6‐MHA) and mercaptosuccinic acid (MSA)} were synthesized by a reproducible aqueous colloidal technique at room temperature. The impact of the capping agents on the size and the crystallinity of the CuSeQD materials, were investigated by small angle X‐ray scattering (SAXS) and X‐ray diffraction (XRD) spectroscopic techniques, respectively. SAXS results confirmed that 6‐MHA‐CuSeQD had the smallest average particle core size when dried, whereas MSA‐CuSeQD had the smallest size in aqueous solution, though with a tendency to aggregate. Dynamic light scattering (DLS) measurements indicated strong bonding of the capping agents to CuSe particles, with MSA being the weakest binding agent, as confirmed by comparatively, low Zeta potential(ζ=−31.1 mV) and high polydispersity index (0.469) values. UV‐Vis absorption studies confirmed a large blue shift of the band gap for the QD compared to the bulk material, with characteristic absorption band (λ) and direct band gap (Egd) values being (λ=435 nm, Egd=8.0 eV), (λ=400 nm, Egd=5.6 eV) and (λ=340 nm, Egd=4.0 eV), for 6‐MHA‐CuSeQD, 3‐MPA‐CuSeQD and MSA‐CuSeQD, respectively. As supported by the formal potential values for 6‐MHA‐CuSeQD (E0′≈120 mV), 3‐MPA‐CuSeQD (E0′≈159 mV) and MSA‐CuSeQD (E0′≈183 mV), the smaller the particle size, the lower the potential required for the application of the quantum dots in an electron transfer process.

Synthesis, characterization and antitumor activity of novel ferrocene-coumarin conjugates

Seven novel ferrocene-coumarin conjugates, namely FcL1~FcL7, were synthesized and confirmed by 1H NMR, FT-IR, elemental analysis. The crystal structure of FcL3 was determined by X-ray diffraction, showing that the dihedral angle between the coumarin and the substituted cyclopentadienyl ring was 80.67°. The electrochemical behaviors of FcL1~FcL7 exhibited similar quasireversible redox waves, while the formal potential E0 values of FcL1~FcL5 were distinctively lower than FcL6 and FcL7 due to electronic-effect of substituents. Notably, the title compounds, when screened on human tumor cell lines (MCF-7, BIU-87, SGC-7901, EC-9706, Eca-109 and Jurkat), exhibited potent and broad spectrum activities. Among them, FcL1~FcL5 exhibited more toxicity to most cancer cell lines than FcL6 and FcL7 because of the lower E0. Remarkably, FcL4 showed significant in vitro cytostatic effect on BIU-87 cell line giving respective IC50 values of 1.09 μmol/L, which was much better than that of Adriamycin (IC50 = 6.09 μmol/L). The cytotoxicity assay against SGC-7901 cells also revealed that the complex FcL5 (IC50 = 3.56 μmol/L) was superior to the reference drug Adriamycin (IC50 = 5.44 μmol/L). Consequently, ferrocene-coumarin conjugates are potential candidates for developing metallodrugs with impressive anticancer activity.

Interrogating the Electrochemical Potential of Senna obtusifolia Mediated Biosynthesized Silver Nanoparticles

Hazards and toxicity associated with the physical and chemical synthesis protocol of metal nanoparticles has recently led researchers to seek alternative routes that is eco-friendly, cheap and fast; the green chemistry approach where plant extracts and microorganisms are used in the reduction of the metal salt is fast gaining popularity in the field of nanobiotechnology. However, controversy still trails acceptability; furthermore, electrochemical studies on these metal nanoparticles are limited. In this study, silver nitrate was reduced to its “nano silver form” through a one-step synthesis protocol using leaf extract of Senna obtusifolia . The usual microscopic and spectroscopic techniques such as UV-vis., FTIR, SEM, AFM and XRD were used to confirm the formation of silver nanoparticles. Electrochemical characterization using cyclic voltammetry and impedance spectroscopy further reveals the formation of silver nanoparticles via a redox process of Ag 1+ to Ag 0 with a formal potential value of 0.61 V vs. Ag|AgCl 3 M KCl.

Probing the Fen +/Fe(n − 1)+ redox potential of Fe phthalocyanines and Fe porphyrins as a reactivity descriptor in the electrochemical oxidation of cysteamine

The Mn+/M(n−1)+ redox potential of MN4 macrocyclic molecular catalysts is a very good reactivity descriptor for several electrochemical reactions. One important feature about this reactivity descriptor is that it can be determined experimentally under the same conditions of the kinetic measurements in contrast to other descriptors like intermediate binding energies that are estimated from DFT calculations. However a linear correlation between both descriptors seems to exist. Plots of activity as (logj)E at constant E versus the Mn+/M(n−1)+ redox potential gives volcano correlations. Another important aspect about this parameter is that it is possible to tune the Mn+/M(n−1)+ redox potential of the MN4 catalyst by manipulating the structure of the macrocyclic complex and tailoring the electron-withdrawing power of the ligands to obtain the maximum activity. In this work we have probed the redox potential as a reactivity descriptor for the oxidation of cysteamine studying a series of substituted Fe phthalocyanines and Fe porphyrins adsorbed on glassy carbon and pyrolytic graphite in alkaline media. As expected the catalytic activity of these FeN4 species varies strongly with the Fe (II)/(I) redox potential of the different Fe phthalocyanines and a plot of activity as (logj)E versus E°Fe(II/I) gives a volcano-shaped correlation so a formal potential value exists for which the highest activity can be achieved demonstrating that the formal potential of the complexes seems to be an universal reactivity descriptor for electrochemical reactions.

Coordination, redox properties and SOD activity of Cu(II) complexes of multihistidine peptides

The results of electrochemical and SOD activity measurements of such copper(II) complexes of terminally protected multihistidine peptides that may mimic the active site of CuZnSOD enzyme are submitted and completed with solution equilibrium studies of some copper(II)-ligand systems. The equilibrium data confirm that the thermodynamic stabilities increase with the increasing number of histidyl residues in the amino acid sequence, the stability order, however, can be finely tuned by the number and quality of amino acids between histidine residues. Based on the cyclic voltammetric studies we concluded that the formal reduction potential values of imidazole nitrogen coordinated complexes decrease with the increasing number of imidazole donor atoms in the coordination sphere. However, the redox parameters of [CuH−1L]+ and [CuH−2L] complexes containing amide nitrogen coordination can be determined as well. All formal potential values of [CuL]2+, [CuH−1L]+ and [CuH−2L] complexes fall in the middle potential range of SOD activity. Finally, after the detailed analysis of species distribution curves based upon the equilibrium data SOD activity of copper(II) containing systems at two pH (pH=6.8 and 7.4) were determined. The imidazole coordinated [CuL]2+ complexes of the multihistidine peptide containing the HXH sequence exhibit the most significant activity, but the presence of amide nitrogen coordinated species with slightly distorted geometry could considerably contribute to the SOD activity.

A Systematic Study of the Mass Transport, Kinetic and Thermodynamic Properties of the FeIII/II Process at Glassy Carbon and Boron-Doped Diamond Electrodes

The heterogeneous electron transfer kinetics (k0 values), mass transport and thermodynamic properties (E0 values) associated with the FeIII/II process have been determined in aqueous solutions containing 0.1M HCl, HClO4, bis(trifluoromethanesulfonyl)imide (HNTf2) or 0.05M silicotungstic acid (H4[α-SiW12O40]) supporting electrolytes. The diffusion coefficient (D) values for FeIII and FeII are dependent on the radius of the electrolyte anion and follow the order D(SiW12O404−)<D(NTf2−)<D(ClO4−)<D(Cl−). The k0 values are found to be smaller at boron doped diamond (BDD) electrodes than glassy carbon (GC) electrodes, and influenced by the ion-pairing between electrolyte anions and FeIII and FeII. Based on the formal potential value, HNTf2 is found to be a more innocent electrolyte than commonly used HClO4 with regard to determine the true k0 values of the outer-sphere [Fe(H2O)6]3+/2+ process. Fourier transformed large amplitude alternating current voltammetry, which provides favorable signal to background ratio, was used to determine k0 values associated with the FeIII/II process in H4[α-SiW12O40] and HNTf2 electrolyte media at GC electrodes and probe the implications of the heterogeneity of the BDD electrode surface on the electrode kinetic determination in H4[α-SiW12O40] electrolyte media.

Transport and Kinetic Aspects of Alkali Metal Ions Intercalation into AVPO4F Framework

The effect of the cation nature is explored for the reaction of alkali metal ions intercalation into the AVPO4F material. Application of electrochemical methods allowed determining the key diffusional and kinetic parameters for Li+, Na+ and K+ intercalation reactions. The obtained formal redox potential values, apparent diffusion coefficients and charge transfer resistance values are contrasted, providing the possibility to assess the variation in the reaction energetics for metal ion insertion/extraction. The observed differences in reaction rates are rationalized in terms of different contributions of ion desolvation and transition through adsorbate layer/electrode interface for various ions.

Fabrication of a third-generation glucose biosensor using graphene-polyethyleneimine-gold nanoparticles hybrid

The present study reports a novel approach for the fabrication of a third generation glucose biosensor based on the immobilization of glucose oxidase (GOx) on graphene-polyethyleneimine-gold nanoparticles hybrid (GNS-PEI-AuNPs) using glutaraldehyde as cross-linking reagent. A pair of well-defined redox peaks with the formal potential and peak separation value of −0.38V and 60mV was observed for the immobilized GOx on a gold electrode modified with GNS-PEI-AuNPs hybrid. The heterogeneous electron transfer rate (ks) for the redox center of the immobilized GOx, flavin adenine dinucleotide (FAD), was found to be 5.4s−1. An increase for the anodic peak current and a decrease for the cathodic peak current were recorded for the immobilized GOx on the modified electrode in the presence of glucose and the absence of oxygen. The obtained results confirmed that the prepared modified electrode presented bioelectrocatalytic activity towards glucose through a direct electron transfer (DET) mechanism. The response of the fabricated glucose biosensor was linear towards glucose in the concentration range between 1 and 100μM with the sensitivity about 93μAmM−1cm−2. The limit of detection (LOD) for glucose sensing was estimated to be 0.32μM (S/N=3).

Novel L-lactic acid biosensors based on conducting polypyrrole-block copolymer nanoparticles.

The development of advanced nanomaterials for the highly efficient electrical detection of biological species has attracted great attention. Here, novel polypyrrole-Pluronic F127 nanoparticles (PPy-F127 NPs) with conducting and biocompatibility properties were synthesized and used to construct a L-lactic acid biosensor that could be applied in biochemical assays. The PPy-F127 NPs were characterized by transmission electron microscopy (TEM), elemental analysis and UV-vis spectroscopy. Lactate oxidase (LOx) structure variation on the PPy-F127 NPs was investigated by circular dichroism (CD). The cyclic voltammetric results indicated that LOx immobilized on the PPy-F127 NPs exhibited direct electron transfer reaction with a formal potential value (E(0)') of 0.154 V vs. SCE. Moreover, the biosensor had good electrocatalytic activity toward L-lactic acid with a wide linear range (0.015-37.5 mM) and a low detection limit of 0.0088 mM. The regression equation was I (μA) = 0.02353c (mM) + 1.4135 (R(2) = 0.9939). The L-lactic acid biosensor had a good anti-interference property towards uric acid (UA), ascorbic acid (AA), glucose and cysteine. The idea and method provide a promising platform for the rapid development of biosensors that can be used in the detection of biological species.

Thermodynamics of Fullerenes Reduction Revisited

The thermodynamics of fullerene C60 electroreduction, and 2′-ferrocenylpyrrolidino [3′,4′;1,2][C60]fullerene electroreduction and electrooxidation has been studied in different aprotic solvents containing tetra(alkyl)ammonium perchlorates as supporting electrolytes using dc cyclic voltammetry and square-wave voltammetry. Obtained values of formal potential were corrected for diffusion potential drop. The electrode processes of C60 reduction are accompanied by the ion pair formation. In each reduction step, one cation of supporting electrolyte is involved. The strength of ionic interaction increase with decrease in the interacting ions size. The association constant of ion pair formation, Ka, also depends on the solvent dielectric constant. A linear relationship between ln Ka and 1/ɛs has been found. The association constants obtained on the base of these relations depend on the solvents dielectric properties. The influence of ion pair formation process on the reduction and oxidation of 2′-ferrocenylpyrrolidino [3′,4′;1,2][C60]fullerene has also been compared. Both, anion formed during fullerene cage reduction and cation produced during ferrocene moiety oxidation are associated with one counter-ion from supporting electrolyte. The cation formed during oxidation much stronger interacts with perchlorate ions in comparison to the anion formed by electroreduction. The influence of ion pair formation on the donor-acceptor energy gap has been also discussed.

Synthesis, characterization, crystal structures and electrochemical studies of organotin(IV) carboxylates

Four new organotin(IV) compounds [Me3SnL] (1), {[Me2SnL]2O}2 (2), Bu2SnL2 (3) and [Bu3SnL] (4), where L = O2C(C2H5)CCHC6H4F have been synthesized by refluxing the corresponding organotin(IV) chlorides with sodium (E)-2-(2-fluorobenzylidene) butanoate (NaL) in dry toluene except 2 for which Me2SnO was refluxed with (E)-2-(2-fluorobenzylidene) butanoic acid (LH) in the same solvent. NaL and all the compounds were characterized by FT-IR, 1H NMR and 13C NMR spectroscopy. NaL and compounds 1 and 2 were also characterized by X-ray single crystal analysis which confirmed a linear polymeric structure for compound 1 and a stannoxane for 2. The structural analyses have shown a bridging behavior of the ligand in trimethyl- and tributyl-, chelating as well as bridging behavior in dimethyl- and a chelating bidentate mode of coordination in dibutyltin(IV) compound which is also confirmed from the crystal analysis for compounds 1 and 2. Cyclic voltammetry was used to evaluate the electrochemical, kinetic and thermodynamic parameters for the electron transfer processes of compounds 1–4. Predominantly adsorption controlled redox processes were exhibited by the slope of log ipvs. −log v plots. The values of the diffusion coefficient (Do) indicated the role of solvent in the mobility of the electro-active species to some extent but the overall rate of the redox process was typical of the adsorption controlled process and could not be explained on the basis of solvation effects. The values of formal potential and charge transfer coefficient were also calculated.

Characterization of CuZnSOD model complexes from a redox point of view: Redox properties of copper(II) complexes of imidazole containing ligands

The systematic electrochemical studies of the copper complexes of various terminally protected tri-, tetra-, penta- and heptapeptides containing histidine in different location and number in the peptide chain and two histidine derivatives were carried out by cyclic voltammetry. The redox parameters of CuL and CuL 2 complexes coordinating exclusively through imidazole nitrogens were determined. For all studied Cu(II) complexes the characteristic redox reactions are quasi-reversible one electron reduction processes. The obtained formal reduction potential values fall into the 200–400 mV potential range supporting the former results that the CuL and CuL 2 complexes of these multihistidine peptides are not only structural but also good functional models of the Cu–Zn-superoxide dismutase (CuZnSOD) enzyme. These observations are confirmed by the results of SOD activity assay in a representative copper(II)–ligand system.

A pH responsive electrochemical switch sensor based on Fe(notpH 3) [notpH 6 = 1,4,7-triazacyclononane-1,4,7-triyl-tris(methylene-phosphonic acid)

The electrochemistry of a macrocyclic metal complex Fe(notpH 3) [notpH 6 = 1,4,7-triazacyclononane-1,4,7-triyl-tris(methylene-phosphonic acid)] reveals that the protonation/deprotonation of the non-coordinated P–OH groups in Fe(notpH 3) affects its formal potential value ( E 0′) considerably. Plotting E 0′ as function of solution pH gives a straight line with a slope of −585 mV pH −1 in the pH range of 3.4–4.0, which is about ten times larger than the theoretical value of −58 mV pH −1 for a reversible proton-coupled single-electron transfer at 20 °C. A sensitive pH responsive electrochemical switch sensor is thus developed based on Fe(notpH 3) which shows an “on/off” switching at pH ∼ 4.0.

A simple method for fabrication of sole composition nickel hexacyanoferrate modified electrode and its application

Nickel hexacyanoferrate film modified gold electrode was prepared by a simple chemical deposition procedure from a fresh prepared solution containing ferricyanide, Ni 2+, and sodium nitrate. The resultant films have solo composition and are significantly stable as compared to the electrochemically deposited NiHCF films. For different concentrations of Na + in the solution, the formal potential values of NiHCF shift according to the Nernstian behavior with a slope of 48 mV in the range of 10 −4 to 1.0 M. The NiHCF film was also used for the electrocatalytic oxidation of ascorbic acid. The anodic peak current observed in cyclic voltammetry increased with the ascorbic acid concentration. At a fixed potential under hydrodynamic conditions, the calibration plot was linear over the ascorbic acid concentration range 0.1–12 mM.