Elmo A. Blubaugh

Chronoamperometry of polymer-modified electrodes: Charge transport by diffusion and migration

Abstract A theoretical analysis of charge-transport phenomena due to both diffusion and electrostatic migration in a polymer-modified electrode is presented for chronoamperometry. Concentration distributions and current-time curves were derived for the simple case of a constant electric field in the polymer film.

Spectroelectrochemistry of a system with product deposition

Abstract An analysis of the spectroelectrochemistry of systems containing a species which deposits onto the electrode is presented. In this model, in addition to the Nernst equation, a thermodynamic condition for phase equilibrium between the deposited and solution species of the product is assumed. Relations between the variables of the Nernst plot were derived and procedures for obtaining the formal potential, number of electrons involved, and the maximum equilibrium concentration of the product are presented. These results are applied to the experimental data on the aqueous solution of the laser dye, 1-methyl-4-(5-phenyl-2-oxazolyl) pyridinium p -toluenesulfonate.

Chronocoulometry of a system with deposition of the product on the electrode

Abstract The charge-time relation for double potential-step large-amplitude chronocoulometry was developed for a system with electrodeposition of the product. The model assumes that the concentration of the product near the electrode cannot be larger than the solubility of the product. This model indicates that the Qr(t>τ) vs. θ plot has a constant slope which is smaller than that of the Q(t τ) vs. θ plot increase linearly with √τ.

Thermal Crosslinking Procedure for Preparing Solvent-Stable Polymer-Film Electrodes

Abstract Published procedures for polymer-film electrodes often give unsatisfactory results because of instability of the film electrode interface or film dissolution. We report a procedure which involves the thermal crosslinking of polymer-film electrodes. These polymer films, prepared from a poly(vinylpyridine/styrene) copolymer, are stable toward a variety of solvents both polar and nonpolar. Electrochemical evaluation of these crosslinked polymer films after chemical derivatization with transition metal-porphyrin. A simple two factor simplex is used to optimize the separation of several ionic naphthylamines by varying the pH and percent methanol in the eluting solvent.

Electrochemical investigation of N-methyl-4-(5-phenyl-2-oxazolyl)pyridinium p-toluenesulfonate: A laser dye with product deposition

Abstract The electrochemical and spectroelectrochemical behavior of N -methyl-4-(5-phenyl-2-oxazolyl)pyridinium p -toluenesulfonate was studied to provide an evaluation of the electrochromic properties of this laser dye. Preliminary cyclic voltammetric experiments provided evidence for the deposition onto the electrode of the product of the electrochemical reduction process. Double potential-step chronocoulometry and spectroelectrochemistry at an optically transparent thin-layer gold-minigrid electrode were used to elucidate the reaction mechanism further. Equations were derived to interpret the spectropotentiostatic Nernst plots which exhibit discontinuities as a result of product precipitation onto the electrode. By fitting the experimental data to these expressions, it was possible to calculate the formal potential (−1.017 V vs. SCE) and number of electrons (1.1) for the redox process plus the solubility of the product (0.27 mmol/L). When this solubility value was used in equations derived for the chronocoulometry model for this system, a value of 5 × 10 −6 cm 2 /s was obtained for the diffusion coefficient of the reduced species. From the forward chronocoulometric step, the diffusion coefficient for the oxidized form, the laser dye cation, was calculated to be 6.8 × 10 −6 cm 2 /s. For redox systems in which there is product deposition, the mathematical treatment described permits the calculation of various thermodynamic and transport properties based on spectropotentiostatic and chronocoulometric data.