PHOTOELECTRIC EFFECTS IN DYE-SENSITIZED ARTIFICIAL LIPID MEMBRANES

Using dyes of known redox potentials the specific mechanisms of dark and light potential generation is analyzed in pigmented lipid membranes. The role of the ionic and electronic conductance, as well as the redox potential gradient is specifically related to the observed open circuit voltage developed across the membrane. The results can be most easily explained by the redox electrode model.     

Quantum chemical simulation of the reaction of methane with gold(I) acetylacetonate and aquaacetylacetonate complexes

The interaction between methane and gold(I) acetylacetonate via electrophilic substitution (reaction (I)) and oxidative addition (reaction (II)) is simulated. In both cases, the formation of the products is thermodynamically favorable: the decrease in energy is 31 kcal/mol for reaction (I) and 26 kcal/mol for reaction (II). The product of reaction (II) is additionally stabilized by Au-H interaction. Both reactions have a low activation barrier and proceed via the formation of structurally different methane complexes reducing the energy of the system by 9.3 kcal/mol for reaction (I) and by 10.9 kcal/mol for reaction (II). The complex [Au(H₂O)(acac)] is also capable of forming methane complexes. These complexes result from a thermally neutral reaction and turn into products after overcoming a low energy barrier. The structure of the complex activating methane in the gold-rutin system is deduced from the data obtained.     

HYDROGEN GENERATION FROM ARTIFICIAL SEA HATER IN A SEMICONDUCTOR SEPTUM ELECTROCHEMICAL PHOTOVOLTAIC CELL

Visible light of the solar spectrum is directly converted to stored chemical energy of hydrogen from artificial sea water in a novel electrochemical photovoltaic cell. The principal element of the cell, modeled after the photosynthetic thylakoid membrane, is a semiconductor septum made of polycrystalline n-CdSe thin film deposited on nickel foil, which separates two aqueous solutions. Under short-circuit conditions, vigorous hydrogen evolution was seen at the Ni surface and continued as long as the cell was operated. The novel cell, the concept of which was derived from pigmented bilayer lipid membrane studies, is easy to construct, simple to operate, and appears to be a practical approach to the photochemical conversion and storage of solar energy.     

On the mechanism of air nitrogen fixation on activated carbon surface in water

High-performance liquid chromatography and gas chromatography were used to reveal formation of hydroxyl radicals in air-saturated water containing activated carbon. Probable mechanisms of OH^· formation are considered. The role of OH^· radicals in the formation of carbene centers on the activated carbon surface is discussed. For interpreting the experimental data on atmospheric nitrogen fixation on activated carbon surface, probable mechanisms of nitrogen activation are explored by quantum-chemical methods. Highly reactive OH^· radicals are unable to react with molecular nitrogen under mild conditions. A high reactivity of singlet and triplet carbenes of different nature on activated carbon surface with respect to N₂ molecules was revealed by density functional theory methods.     

Structure and reactivity of gold cluster protected by triphosphine ligands: DFT study

Structural Chemistry - The structure and reactivity of rhombic Au4 cluster protected by bis(dimethylphosphinomethyl) and phenylacetylide ligands towards CO and O2 were studied in...     

Runaway Electron Beam Instability in Slide-Away Discharges in the HT-7 Tokamak

Slide-away discharges are achieved by decreasing the plasma density or ramping down the plasma current in runaway discharges in the HT-7 tokamak. In the case of plasma current ramp down, the ratio of the electron plasma frequency to the electron cyclotron frequency is higher than in the stationary pulses when the discharge goes into a slide-away regime. The instability regime is characterized by relaxations in the electron cyclotron emission due to relativistic anomalous Doppler effect which transfers energy from parallel to perpendicular motion. The triggering of relativistic anomalous Doppler effect at higher density by ramping down of plasma current may provide a alternative runaway energy control scenario.