Platinum disk electrode

KGS51), hydrogen peroxide (85KGS1042), and a rotating platinum disk electrode (84KGS318). 

Figure 9. Chronoamperometric curves for the growth of a polythiophene film on a stationary platinum disk electrode, from 0.1 M thiophene and 0.1 M LiC104 acetonitrile solutions, at different water contents (---) 0.04%, (--------) 0.14%,...

Fig. 5.44 The voltammogram of molecular hydrogen at a rotating bright platinum disk electrode in 0.5 m H2S04, pHl = 105 Pa, 25°C. The rotation speed

A platinum disk electrode was electrolytically platinized in a platinum chloride solution to increase the surface area and enhance the adsorption power. The platinized platinum electrode was then immersed in a solution containing 10 mg ml l ADH. 0.75 mM and 6.2 mM NAD. After sufficient adsorption of these molecules on the electrode surface, the electrode was transferred into a solution containing 0.1 M pyrrole and 1 M KC1. Electrochemical polymerization of pyrrole was conducted at +0.7 V vs. Ag/AgCl. The electrolysis was stopped at a total charge of 1 C cm 2. An enzyme-entrapped polypyrrole membrane was deposited on the electrode surface. 

Figure 10.1 Kinetic trace for protonation of dihydride FeH2[P(CH2CH2PPh2)3] in THF with an excess of FIBF4 at room temperature. The intensity of current was measured at a platinum disk electrode maintained at —0.1 V with vigorous stirring. (Reproduced with...

Figure 6. Cyclic voltammograms of a platinum disk-electrode modified with a film of the octanuclear dendrimer 2, measured in 0.1 M Bu NPFj/CHjClj. The surface coverage of electroactive ferrocenyl sites in the film is determined to be T = 2.01 x 10" mol cm . inset, scan rate dependence of the anodic peak current.

Fig. 6-6. RDE and HMRDE curves for quinhydrone at platinum. Curve A, RDE traces for cyclic potential scan of 1.00 pM quinhydrone in 0.02 M H2S04 at platinum disk electrode. Curve B, HMRDE traces for the solution in curve A. Curve B, HMRDE residual in 0.02 M H2S04. Conditions QU2 = 60 rpml/2. A 1/2 = 6 rpm1/2. /= 3 Hz, scan rate is 5 mV/s, averaging time constant is 3 s. From [67],...

On the basis of the slopes and the solubilities of H2 in the respective solvents,16 the diffusion coefficients for H2 (DH2) have been evaluated via Eq. (8.29) and arfe summarized in Table 8.4. Rotated platinum-disk electrodes also provide a measure of DH2 values for such measurements are included in Table 8.4.14... 

Electrode and Nafion film Platinum disk electrode (area = 0.28 cm2) was fabricated as previously described (27). A solution of Nafion (EW = 1100) 5% w/v in a mixture of lower aliphatic alcohols and 10% water was obtained from Aldrich and diluted with methanol to give a stock solution of 0.35% w/v. Films of Nafion-glucose oxidase were formed by syringing aliquot (20 pi) of the mixed solution (86.7 pi of Nafion stock solution and 13.3 pi of glucose oxidase solution) at the surface of the platinum electrode. The solvents were left to evaporate at room temperature for at least 30 min. The extra amount of GOD was... 

Electropolymerized films have been used to prevent interferences and fouling in biosensors constructed from reticulated vitreous carbon and platinum disk electrodes (14,15). A biosensor constructed using electropolymerized films can have significantly improved diffusional properties due to the thinness of the film. By engineering the components and properties of a biosensor on a microscopic scale, rather than using "bulk-technology" and physically assembling discrete macroscopic components, as is the conventional practice, an all-chemical method of construction can be achieved. All-chemical methods of construction would... 

The regenerated ionic liquid phase was investigated dectrochemically to determine its quality. Cyclic voltammetry was performed using a rotating platinum disk electrode (500 rpm), a platinum counter electrode and a platinum wire as (quasi ) reference electrode placed closed to the rotating disk. 

Hotta et al. [38] have developed a new electrochemical device for studying ET at the O/W interface, in which the O and W phases are separated by an electron conductor (e.g., Pt). This system is named as electron-conductor separating oil-water (ECSOW) system. As shown in Figure 8.3, the EC phase that separates the O and W phases can be feasibly realized by connecting two platinum disk electrodes with an electric wire. 

FIGURE 8.3. Electrolytic cell for the ECSOW system (a) O phase (b) W phase (c), (d) platinum disk electrodes connected with an electric wire (e), (f) reference electrodes with Luggin capillaries (g), (h) platinum coil electrodes (i), (j) N2 gas inlet. Reprinted from Ref. [38], with permission from Elsevier Science. 

Figure 16. Current decay curves the natural logarithm of the steady-state oxidation plateau current of radical anions (mediators) plotted against time (s) for the following four combinations of mediator/substrate benzophenone/l-bromo-2,2-dimethylpropane (-(-) perylene/l-bromo-2,2-dimethylpropane (x) perylene/l-bromoadamantane ( ) and quinoxaline/2-chloro-2-methyl-propane (O). All measurements were obtained with a 10-pm platinum disk electrode in DMF/0.1 M BU4NBF4 at 22°C. From S. U. Pedersen and K. Daasbjerg, Acta Chem. Scand, 43 30 (1989) [36],...

The cause of this effect of nickel ions was investigated voltammetrically with a gold-plated rotating platinum disk electrode [158]. The current-potential curves shown in Fig. 33 demonstrate that the anodic oxidation of the reducing agent... 

Lowe and co-workers investigated covalent immobilization of enzyme in polypyrrole film [123,124]. First, pyrrole-modified enzyme was prepared by reacting glucose oxidase with either W-(3-aminopropyl)pyrrole or N- 2-carboxyethyl)pyrrole, then electropolymerized enzyme films, which covalently immobilize enzyme were deposited at platinum disk electrodes from solutions of free pyrrole and native or pyrrole modified enzyme of equivalent activity. They observed that sensors constructed of covalently electropolymerized GOx films demonstrated higher enzyme activity than those using entrapped native... 

Recent development in multilayer sensor architecture using sequential electrochemical polymerization of pyrrole and pyrrole derivatives to entrap enzymes was tested on a tyrosinase-based phenol sensor [127]. A phenothia-zine dye, thionine served as redox mediator and was covalently attached to the thin, functionalized first polypyrrole layer on Platinum disk electrodes. Then, a second layer of polypyrrole with entrapped tyrosinase was electrochemically deposited. The phenol sensor constructed in this manner effectively transferred electron from enz3Tne to the electrode surface. As all steps in preparation, including deposition of the enzyme-containing layer are carried out electrochemically, this technique may prove to be applicable for mass production of miniature sensors. 

Hexafluorophosphates are slightly more resistant toward anodic oxidation than tetrafluoroborates and perchlorates [444] in a 0.1 M solution of these salts in acetonitrile the potentials (versus Ag/0.1 M Ag" " electrode) at a platinum disk electrode (0.12 cm2) 1 mA were for perchlorate, 2.48 V for tetrafluoroborate, 2.91 V and for hexafluoropho-sphate, 3.02 V [444]. Hexafluoroarsenates have been used in liquid SO2 [432,433]. 

Electrochemical experiments in this study were performed with a BAS-KX) Electrochemical Analyzer (Bioanalytical Systems Inc., Lafayette, Indiana). For potentiometric experiments in calm solutions, platinum disk electrodes were used in the BAS-100 cell stand. For hydrodynamic experiments a Pine Instruments Inc. rotating-disk platinum electrode was interfaced with the BAS-100. 

A rotating platinum disk electrode was used for gathering data for the calculation of the kinetic constants. Tafel plots (5) were developed (Figure 2), from which the heterogeneous rate constants, k , and the electron-transfer coefficients, a, were determined. In all determinations of kinetic parameters, a blank voltammogram, run under identical conditions, was subtracted from the data to remove current due to background reactions or charging of the double layer. 

Figure 2. Tafel plots of oxidation and reduction of iron at pH 3 in 0.1 m KCl determined at a rotating platinum disk electrode. Currents are extrapolated values for an infinite rate of rotation. Temperature = 298 1 K.

Table H. Heterogeneous electron-transfer kinetics at the platinum disk electrode at 298 K. All values determined from linear portions of Tafel plots at rates of rotation extrapolated to infinity. Reaction of Se and As too slow for observation...

A solution of volume 50 cm contains 2.0 X 10 M Fe and 1.0 X 10 M in 1 M HCl. This solution is examined by voltammetry at a rotating platinum disk electrode of area 0.30 cm. At the rotation rate employed, both Fe and have mass-transfer coefficients, m, of 10 cm/s. (a) Calculate the limiting current for the reduction of Fe under these conditions, (b) A current-potential scan is taken from +1.3 to —0.40 V vs. NHE. Make a labeled, quantitatively correct, sketch of the i-E curve that would be obtained. Assume that no changes in the bulk concentrations of Fe and Sn " occur during this scan and that all electrode reactions are nemstian. 

The formal redox potentials /s 1/2 of some Tc(ll) complexes determined by cyclic voltammetry are given in Table 12.17.A. The ]/2 values were calculated from the average of the anodic and cathodic peak potentials, 1/2 = ( p,a-i- p.c)/2. The potentials were measured with a platinum disk electrode v.v SCE in acetonitrile containing... 

Figure 14-7. Cyclic voltammogram demonstrating mediated electron transfer from glucose oxidase to a platinum electrode with ferrocene carboxylic acid, a) 2mM ferrocene carboxylic acid b) +10 mg glucose oxidase c) +30 mg glucose. —100 to +700 mV vs. SCE 5 mV s 0,1 M phosphate buffer (ph 7.4) with 0.5 M NaCl platinum disk electrode, 1 mm diameter.

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