Showing papers on "Cyclic voltammetry published in 1994"
TL;DR: In this paper, a theory for electrode kinetics of surface-immobilized monolayers in cyclic voltammetry is developed based on the Marcus free energy-rate relation.
Abstract: : Theory for electrode kinetics of surface-immobilized monolayers in cyclic voltammetry is developed based on the Marcus free energy-rate relation. Numerical calculations show that when the applied over-potential exceeds ca. 30% of the reorganizational energy of the electrode reaction, voltammetry predicted from Marcus theory differs from that based on classical Butler-Volmer kinetics with regard to waveshape, peak currents and their dependence on potential sweep rate, and variation of peak potential with potential sweep rate. Estimates of the standard rate constant, K deg, can be made from E peak data without exact knowledge of reorganizational energies. Examples are given of evaluating K deg for monolayers of ferrocene alkanethiols chemisorbed on Au(111) electrodes, when the monolayers are highly ordered, and kinetically monodisperse, and when they are somewhat disordered, and kinetically disperse on bulk gold electrodes at room and 150K temperatures. Electrode kinetics, Monolayers, Cyclic voltammetry, Marcus equation.
220 citations
TL;DR: In this paper, in situ infrared (FTIR) spectroscopy and differential electrochemical mass spectrometry (DEMS) was used to study the adsorption and electrooxidation of CO on polycrystalline Pt and PtRu alloys.
219 citations
TL;DR: In this article, the chemical inertness and corrosion resistance of a boron-doped diamond thin film electrode, grown by chemical vapor deposition (CVD), have been studied during potential cycling (PC) for 2 h in a solution of at 50°C.
Abstract: The chemical inertness and corrosion resistance of a boron‐doped diamond thin film electrode, grown by chemical vapor deposition (CVD), have been studied during potential cycling (PC) for 2 h in a solution of at 50°C. Similar experiments were performed on highly ordered pyrolytic graphite (HOPG) and glassy carbon (GC), for comparison. The physicochemical properties of the electrode surface were characterized before and after PC by cyclic voltammetry, optical and scanning electron microscopy, Raman spectroscopy, and ac impedance spectroscopy. The results indicated that the diamond electrode possesses a superior degree of chemical inertness and corrosion resistance, has no microstructural damage nor was surface oxidation observed after PC. HOPG and GC surfaces, on the other hand, exhibited severe corrosion in the form of surface cavitation, pitting, and oxidation. The relative degree of microstructural damage and surface oxidation increased in the order of diamond . This work represents some of the initial efforts at systematically characterizing how the physical, chemical, and electronic properties of conductive diamond thin films are affected during exposure to electrochemical conditions (i.e., solvent, electrolyte, and applied potential).
218 citations
TL;DR: The properties of a glassy carbon (GC) electrode modified by nickel hydroxide formed by ex situ chemical precipitation were studied by cyclic voltammetry in alkaline solutions.
200 citations
24 Jul 1994
TL;DR: In this article, a new series of alternating copolymers based on poly(p-phenylenevinylene) (PPV) was synthesized, and the electron affinity of the polymers was substantially increased through the use of electron-withdrawing substituents.
Abstract: Summary form only given. A new series of alternating copolymers based on poly(p-phenylenevinylene) (PPV) was synthesized. The electron affinity of the polymers is substantially increased through the use of electron-withdrawing substituents. Optimum conditions for the condensation polymerization were explored, and polymers with a M/sub n/ in excess of 30,000 were produced. The synthesis is extremely flexible and allows a large variety of conjugated polymers with different emission properties to be synthesized. Cyclic voltammetry was used to estimate the position of the HOMO and LUMO relative to poly(2,5-dialkoxy-1,4-phenylenevinylene) analogues. Fabrication of efficient bilayer polymer LEDs using PPVin conjunction with the new polymers and stable metal negative contacts such as aluminum and gold is reported.
187 citations
TL;DR: In this article, the formation of nickel hydrides in the potential region of the her was previously analyzed by cyclic voltammetry and the electrode surface was pre-conditioned to minimize the effect of the hydride in the experimental response of the system.
186 citations
TL;DR: In this article, the PQQ-modified electrodes were used for covalent immobilization of pyrroloquinoline quinone (PQQ) as a monolayer by carbodiimide coupling of the pQQ carboxylic groups with the surface amino groups.
178 citations
TL;DR: These flavonoids were shown to undergo homogenous chemical reactions following oxidation at a glassy carbon electrode, and two products did not correspond to previously reported products of enzymatic oxidation.
174 citations
TL;DR: In this article, the adsorption and anodic oxidation of DNA denatured in acid at glassy carbon electrodes using differential pulse, square wave and cyclic voltammetry, and impedance have been obtained, in the pH range 0-12 and as a function of adsorization potential and time of adaption.
143 citations
126 citations
TL;DR: In this paper, the electro-oxidation and -reduction of 0.05 M ammonia, 0.01 M hydroxylamine and 0.5 M KOH at Pt-black electrodes has been investigated using a combination of cyclic voltammetry with on-line MS analysis of volatile products.
TL;DR: Dopamine permeates the film more quickly with constant-potential amperometry than with repeated fast-scan cyclic voltammetry as predicted by diffusion equations, and it is demonstrated that the temporal delay caused by diffusion through Nafion film can be removed by deconvolution procedures.
TL;DR: In this paper, a metal-free 2,9,16,23-tetraferrocenylphthalocyanine was synthesized in dichloroethane.
TL;DR: In this article, the electrochemical behavior of thiocholine at screen-printed carbon electrodes chemically modified with cobalt phthalocyanine was investigated, and the optimum potential for amperometric studies was found to be + 0.1 V.
Abstract: Cyclic voltammetry was used to investigate the electrochemical behaviour of thiocholine at screen-printed carbon electrodes chemically modified with cobalt phthalocyanine. Cyclic voltammograms exhibited one anodic peak (Ia) and two cathodic peaks (Ic and IIc) in the potential range –0.8–+0.3 V between pH 5.0 and 12.0. Peak Ia is considered to result from the electrocatalytic oxidation of the thiol moiety to produce the corresponding disulfide; peak Ic is likely to be the electrocatalytic reduction of the disulfide back to the original thiol species. Peak IIc is probably due to a reduction process occurring in the macrocyclic phthalocyanine molecule. Hydrodynamic voltammetry was performed in 0.05 mol dm–3 phosphate buffer (pH 8.0) containing thiocholine; one well-defined anodic wave was obtained. From this, the optimum potential for amperometric studies was found to be +0.1 V. Calibration studies were performed using amperometry in stirred solution; a linear response was obtained over the range 5.0 × 10–7–4.8 × 10–5 mol dm–3. It should be possible to use these screen-printed electrodes as the basis of a pesticide sensor.
TL;DR: In this paper, self-assembled monolayers with attached redox centers are characterized by their reversible behavior and their electron transfer kinetics in a range of nonaqueous solvents: methanol, ethanol, propanol, butanol, acetonitrile, N,N-dimethylformamide, dimethylsulfoxide, propylene carbonate, acetone, and tetrahydrofuran.
Abstract: Self-assembled monolayers with attached redox centers are characterized by their reversible behavior and their electron-transfer kinetics in a range of nonaqueous solvents: methanol, ethanol, propanol, butanol, acetonitrile, N,N-dimethylformamide, dimethylsulfoxide, propylene carbonate, acetone, and tetrahydrofuran. The monolayers are formed by coadsorbing the thiols HS(CH 2 ) n CONHCH 2 pyRu(NH 3 ) 5 (PF 6 ) 2 and HS(CH 2 ) n COOH (n= 10 or 15) on gold electrodes. The monolayer-coated electrodes are examined by cyclic voltammetry and chronoamperometry first in the nonaqueous electrolyte and then in an aqueous electrolyte
TL;DR: In this paper, the copolymerization of 2,5diaminobenzensulfonic acid (DABSA) and aniline (AN) was performed electrochemically by cyclic voltammetry on titanium electrodes in 1M.
Abstract: Copolymerization of 2,5‐diaminobenzensulfonic acid (DABSA) and aniline (AN) was performed electrochemically by cyclic voltammetry on titanium electrodes in 1M . The copolymerization rate is strongly dependent on the amount of DABSA in the comonomer feed. The compositions of the copolymeric films were determined by x‐ray photoelectron spectroscopy and were controlled by changing comonomer feed ratios. The copolymer compositions can be expressed in terms of comonomer feed ratios by a simple copolymer model showing that the reactivity ratio of aniline increases by increasing the amount of DABSA in the comonomer feed. The composite film of DABSA‐AN copolymer with waterborne polyurethane was prepared and its conductivity was measured for comparing the effect of DABSA in the comonomer feed. Scanning electron microscope (SEM) photographs show that there exist clear differences in morphology of the polymer films at various DABSA concentrations.
TL;DR: Sulfonated polyaniline (SPAN) was synthesized by sulfonation of PANI base with fuming sulfuric acid as discussed by the authors, which led to ca. 47% sulfonations of an otherwise unchanged polyanile backbone, which was used as a cation insertion material for battery and electrochromic applications.
Abstract: Sulfonated polyaniline (SPAN) was synthesized by sulfonation of polyaniline (PANI) base with fuming sulfuric acid. Thin films were cast from polymer solutions in basic media. The polymer films were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible–near-infrared spectroscopy, scanning electron microscopy (SEM) and cyclic voltammetry. XPS in combination with FTIR showed that the preparation procedure led to ca. 47% sulfonation of an otherwise unchanged polyaniline backbone. The NIR spectra of SPAN films showed a polaron band at higher energies than with polyaniline. This is in agreement with the lower conductivity of SPAN as compared with polyaniline. SEM micrographs of the SPAN films showed a compact globular morphology. Electrodes modified with thin SPAN films exhibited two redox steps, both in aqueous and in non-aqueous electrolytes. The specific charge stored in SPAN films was found to be ca. 37 A h kg–1 in aqueous solution (only the first redox step) and ca. 68 A h kg–1 in non-aqueous media (both redox steps). A practical SPAN–Li battery could have 50% more specific energy than a PANI–Li battery. The optical spectra of SPAN films exhibited bands at 310, 450 and 750 nm, the intensities of which changed during the redox process. The absorption coefficients of SPAN (emeraldine base state) solutions had values of a= 410 at 313 nm and a= 239 at 563 nm. The suitability of SPAN for use as a cation-insertion material for battery and electrochromic applications is discussed.
TL;DR: In this paper, the effect of base metal oxide (nonnoble metal oxide) in a Pt-Cr-Cu alloy catalyst is investigated for the oxygen reduction reaction in a solid polymer-electrolyte fuel cell.
Abstract: The effect of base metal oxide (nonnoble metal oxide) in a Pt-Cr-Cu alloy catalyst is investigated for the oxygen reduction reaction in a solid-polymer-electrolyte fuel cell. The cathode mass activities at 0.9 V for Pt, Pt-Cr alloy, Pt-Cr-Cu alloy, and a mixture of Pt-Cr-Cu alloy with base metal oxide are compared. The enhancement factor is largest (about 6 times) for the mixture of Pt-Cr-Cu alloy with base metal oxide, compared to Pt-Cr and Pt-Cr-Cu alloys (about 2 times). The higher electrocatalytic activity of this material may be due to the combined effects of the Pt-Cr-Cu alloy and the base metal oxide. The physical and electrochemical characterizations are carried out using various techniques like X-ray diffraction, transmission electron microscopy, cyclic voltammetry, polarization, and ac impedance.
TL;DR: The layered double hydroxide (LDH) Zn 2 Cr(OH) 6 Cl · 2H 2 O, denoted [Zn-Cr-Cl], which is an anion-exchanging clay, is rapidly exchanged with electroactive organic sulphonate anions such as m -nitrobenzene sulfonate and anthraquinone mono- and disulphonates as mentioned in this paper.
TL;DR: In this article, the effects of the terminal groups on the redox responses of Fe(CN) 3−6, Ru(NH 3 ) 3+6 and 1,1′-ferrocenedimethanol (FcDM 0 ) aqueous solutions were investigated by cyclic voltammetry.
TL;DR: In this article, cyclic voltammetry on IrO2-coated titanium electrodes in 0.5m H2SO4 was used for copolymerization of aniline (AN) and para-phenylenediamine (PPDA).
Abstract: Copolymerization of aniline (AN) and para-phenylenediamine (PPDA) was electrochemically performed by cyclic voltammetry on IrO2-coated titanium electrodes in 0.5m H2SO4. The cyclic voltammograms, with and without a middle peak at about 580 mV, can be produced by controlling the PPDA concentration in the aniline solution during polymer preparation. The peak at about 580 mV corresponds to the para-aminophenol/benzoquinoneimine (PAP/QI) redox couple and crosslinking sites. The mass of polymer deposited on an IrO2-coated titanium electrode is correlated with the polymer anodic peak current, which allows the rates of polymer deposition to be monitored by increases in the anodic peak current at various PPDA concentrations. SEM photographs show that the morphology of the polymer film depends dramatically on PPDA concentration. Stability test information can be used in generating an effective index to discern between the crosslinking and the PAP/QI reactions induced by PPDA. The linear relationship between the second redox process potential (E
1/2), corresponding to the oxidation and reduction between polaronic emeraldine and pernigraniline in PPDA-modified PANI films, and pH, possesses a slope of about -120 mV/pH.
TL;DR: In this article, the authors used cyclic voltammetry and rotating disk voltammetrics to study the oxidation of carbohydrates at several copper-oxide-modified electrodes in alkaline solution.
TL;DR: Non-cross-linked and also cross-linked poly(ether amine quinone)s were prepared and tested for their efficiency as electron-transfer relay systems in amperometric glucose biosensors and showed efficiently mediated electron transfer from reduced glucose oxidase to a conventional carbon paste electrode.
Abstract: Non-cross-linked and also cross-linked poly(ether amine quinone)s were prepared and tested for their efficiency as electron-transfer relay systems in amperometric glucose biosensors. Cyclic voltammetry and constant applied potential measurements showed that poly(ether amine quinone) relay systems efficiently mediated electron transfer from reduced glucose oxidase to a conventional carbon paste electrode. Sensors containing these relay systems respond rapidly to low (< 0.1 mM) glucose concentrations and reach steady-state current responses in less than 1 min. Electrodes constructed with cross-linked polymer and glucose oxidase were stable, indicating that the glucose oxidase was trapped in the polymer matrix and did not freely diffuse away from the electrode surface into aqueous solutions. The cross-linked polymer is a large molecular system which facilitates a flow of electrons from enzyme to the electrode, acting as an electron-transfer relay system and not as a diffusional mediator.
TL;DR: In this article, an unexpectedly large increase in surface mass was observed during the positive potential scan in the pre-oxide region beginning ca. 0.5 V negative of the potential for onset of formation of surface oxide (AuO).
TL;DR: Amperometry in stirred solution has been used for the systematic evaluation of modified screen-printed carbon electrodes (SPCEs) with a view to developing a reagentless biosensor for uric acid, suggesting that the process is diffusion-controlled and not governed by the kinetics of the enzyme.
Abstract: Amperometry in stirred solution has been used for the systematic evaluation of modified screen-printed carbon electrodes (SPCEs) with a view to developing a reagentless biosensor for uric acid. The developed system consists of a base cobalt phthalocyanine (CoPC) electrode tailored to the electrocatalytic oxidation of H2O2 by means of a cellulose acetate (CA)–uricase bilayer. Uricase was immobilized by drop-coating the enzyme onto the CA membrane covering the CoPC-SPCE. The device exploits the near-universal H2O2-generating propensity of oxidases, the permselectivity of the CA film towards H2O2 and the electrocatalytic oxidation of this product at the CoPC-SPCE. The electrochemical oxidation of the resulting Co+ species was used as the analytical signal, facilitating the application of a greatly reduced operating potential when compared with that required for direct oxidation of H2O2 at unmodified electrodes. The time required to achieve 95% of the steady-state current (t95iSS) was 44 s [relative standard deviation = 7.5%(n= 10)]. Amperometric calibrations were linear over the range from 13 × 10–6 to 1 × 10–3 mol dm–3, with the former representing the limit of detection. The CA membrane extended the linear range of the biosensor by over two orders of magnitude, when apparent Michaelis–Menten constants (Km′) of immobilized and free enzymes are compared. This suggests that the process is diffusion-controlled and not governed by the kinetics of the enzyme. The precision of electrode fabrication was determined by cyclic voltammetry to be 4.9%(n= 6). Successive amperometric calibrations (n= 7) over 7 d using a single sensor revealed only a 14.0% diminution in sensitivity from the original response. Sensor stability and the dependence of the steady-state current on the pH, ionic strength and temperature of the supporting electrolyte were studied and the results are presented. The functioning of the biosensor is indifferent to a wide range of potential interferences studied in a synthetic sample and results correlate favourably with those of a standard hospital method.
TL;DR: In this paper, the effect of nitrite and chromate inhibitor ions in varying concentrations on the corrosion of aluminium in near neutral chloride solution has been studied using measurements of the open circuit potential and its variation with time, cyclic voltammetry, potential step chronoamperometry and electrochemical impedance measurements.
TL;DR: In this article, the influence of the π-electron count on cyclic voltammetry (CV) has not yet been investigated in detail, though six electrons can be reversibly added to C{sub 60] and the effect on CV has been investigated.
Abstract: Though six electrons can be reversibly added to C{sub 60}, the influence of the {pi}-electron count on cyclic voltammetry (CV) has not yet been investigated in detail. Saturation of a double bond of C{sub 60} in methanofullerenes causes a negative shift of about 50-150 mV for the first three waves. Here we report the synthesis and electrochemical investigation on a p-(methoxycarbonyl)-phenyl-substituted fulleroid (2) and its methanofullerene isomer (3). Further, by a combination of CV and UV - vis spectrophotometry, we show that (1) 2 and 3 have only very slightly different electron acceptor character and (2) 2 is converted to 3 upon addition of a third electron in 2. 13 refs., 2 figs.
TL;DR: In this article, the Tafel slope changes on electrodes aged by H2 evolution: it varies from about 60 mV for pure RuO2 to about 20 mv for pure IrO2, and the apparent reaction order varying from 1 to ca. 2.5.