Generation of the Trifluoromethyl Radical from Freons F13 and F13B1 and the Laser Photoelectron Emission Determination of Its Redox Potential

The redox potentials of the trifluoromethyl radical obtained experimentally by the laser photoelectron emission (LPE) method and by solution of the diffusion-kinetics problem involving the adsorption, desorption, electron transfer, and annihilation in the bulk of both the radicals and the products of their electrode reactions were compared. The usefulness of the LPE method for determining the redox potentials and rate constants of redox reactions of the CF^middot ₃ radicals was demonstrated.     

Photorefractive Properties of Photochemically Modified Poly(hydroxyaminoether)

The exposure of photosensitive poly(hydroxyaminoether)-based polymer compositions to light leads to the formation of an image with nonlinear optical and photoelectric properties and, hence, photorefractive behavior. Using the holographic birefringence technique, it was shown that the pumping of one of laser beams (signal beam) at the expense of the intensity of another (reference beam) takes place in the photochemically modified regions of the polymer layer. Unlike the majority of the previously studied photorefractive polymeric media, the beam-coupling gain coefficient (cm^–1) exceeds the absorption coefficient (cm^–1); i.e., the intensity of the signal beam after passing the layer becomes higher than that before the layer. A net internal gain, i.e. the difference – , of 117 cm^–1is achieved at E ₀= 26 V/m. The photorefractive effect is absent from the unexposed areas of the layer.     

Comparative Study of Graphite and the Products of Its Electrochemical Exfoliation

Russian Journal of Electrochemistry - A comparative study of electrochemical characteristics of graphite electrodes and precipitates of suspensions produced by the graphite exfoliation is carried...     

Electrochemical Behavior of Electrodes Containing Single-Walled Nanotubes

The differential capacitance and voltammograms of electrodes that contain single-walled carbon nanotubes are measured in aqueous electrolytes. The discovered dependence of the capacitance on the measurement frequency is attributed to structural features of nanomaterials used. Electrochemical characteristics of nanotube electrodes are close to those of glassy carbon electrodes, with the difference that the discharge current in the former is substantially higher at cathodic potentials in the presence of N₂O. This effect is presumably caused by an autoelectron emission of electrons from nanotubes into electrolyte.     

Photorefractive Composites Based on Nanocrystalline Carbocyanine Dye J-Aggregates with a Fast Response Time

The use of carbocyanine dye J-aggregates as sensitizers of photoelectric sensitivity and chromophores with the third-order nonlinear optical polarizability made it possible, by the action of two intersecting He–Ne laser (633 nm) beams and an applied electric field, to obtain photorefractive spatial modulation of the refractive index in a nonplasticized polymer layer having the glass transition temperature of about 230°C with a short (20 ms) time of response to this action. A fairly high two-beam-coupling gain coefficient was obtained, which reached a value of = 218 cm^–1 at an applied field of E ₀ = 50 V/m. The net internal gain (difference between the beam-coupling gain coefficient and the absorption coefficient ) was – = 143 cm^–1 under these conditions.     

Electron injection from nanostructured carbon electrodes at moderate cathodic potentials

Voltammograms of electrodes based on nanostructured carbon of different morphology (single-wall carbon nanotubes, carbon nanofilaments, columnar structures) are taken in hexamethylphosphortriamide solutions. For all listed electrodes, direct experimental proof of the electron injection to the electrolyte solution at moderate cathodic potentials is obtained. It is found that this phenomenon is associated with the existence of atomically sharp spots at the electrode surface, which operate as local cathodes for the electron emission. It is shown that the current-voltage characteristics for the electron injection to the electrolyte solution differ from those for the field electron emission current at the electrode/vacuum interface.     

Spectroscopy of Molecular Crystals,A Bibliography for 1982

The 1982 Bibliography continues the series of annual issues of Bibliographies Spectroscopy of Molecular.     

Mechanism of Electrode Reactions Involving Carboxymethyl and Chlorocarboxymethyl Radicals and Ion-Radicals

Mechanism of reduction and oxidation of carboxymethyl and chlorocarboxymethyl radicals and ion-radicals adsorbed on a mercury electrode is studied by a laser photoemission method in broad ranges of potentials and solution pH. Versions of reduction and oxidation depend on the solutions" acid–base properties. In acid solutions, a metastable complex ion-radical–(radical)–proton donor undergoes reduction. In neutral and weakly alkaline solutions, the electron transfer onto an ion-radical dominates. In strongly alkaline solutions, a metastable complex ion-radical–proton donor undergoes reduction. The last complex is oxidized in neutral and alkaline solutions at anodic potentials, whereas in acid solutions carboxymethyl radicals and ion-radicals are oxidized. Kinetic parameters of metastable complexes barely depend on the presence of the chlorine atom in the radical, in contradistinction to the reduction overvoltage of ion-radicals and their complexes, which discernibly diminishes following halogenation. The experimental data are interpreted within an earlier model for electrode reactions involving intermediates, which includes two parallel channels for the electron transfer: adsorbed radical (anion-radical) to electrode and metastable complex radical (anion-radical) to donor/acceptor of protons to electrode.