Photoexcited Dye Molecules Research Articles

Organo-modified metal oxide electrode Part V. Efficiency of electron injection into conduction band from photo-excited dye molecule covalently attached to an SnO2 surface

Organo-modified metal oxide electrode Part V. Efficiency of electron injection into conduction band from photo-excited dye molecule covalently attached to an SnO2 surface

Organo-modified metal oxide electrode: Part V. Efficiency of electron injection into conduction band from photo-excited dye molecule covalently attached to an SnO 2 surface

Organo-modified metal oxide electrode: Part V. Efficiency of electron injection into conduction band from photo-excited dye molecule covalently attached to an SnO 2 surface

Quantum Efficiency and Photoconductivity in Dye-Sensitized ZnO-Resin Binder Layers

Measurements of quantum efficiency and photoconductivity on dye-sensitized ZnO powder-organic-resin binder layers as used in electrophotography show that the carrier range for dye-sensitized photocurrents is 10 to 100 times lower than that for the intrinsic ZnO photocurrent at 3800 Å. The dye-sensitized photocurrent depends on the square root of light intensity while the photocurrent at 3800 Å is linear with intensity. These observations are interpreted in terms of a bimolecular recombination process for the dye-sensitized photocurrent in which a photoexcited dye molecule injects an electron into the ZnO conduction band and then recaptures ZnO conduction electrons to return to the ground state.

Relation between Fermi Level of Dyes and Redox Reaction caused by the Photo-excited Dye Molecules

WE have previously suggested that spectral sensitization in photography is governed by the relative position of the Fermi level of the photographic dyes with respect to the intrinsic Fermi level of silver halide1. The spectral sensitization of the photographic process is regarded as the reduction of silver halide caused by the photo-excited dye molecules. It is therefore suggested that the redox reaction caused by the photo-excited dye molecules is also determined by the Fermi level of the dyes.

Electronic spacial and surface properties of zinc oxide

The equilibrium electrophysical parameters (electroconductivity work function) of semiconductor gas sensor surfaces are insufficient for the characterization of adsorption selectivity. The energy spectrum of surface electron states corresponding to the gas and vapour adsorption is quasicontinuous and does not reflect the individual properties of detecting molecules properly. Some types of vibronic (electron–vibrational) interactions arising in adsorption charging of the sensor surface are proposed to produce selectivity. Some vibronic effects are examined in the following situations: (1) At the adsorption of excited gas molecules (Ov=12, Zn/ZnO); (2) at the vibrational excitation of detecting molecules in deactivation events of previously adsorbed photoexcited dye molecules (H2O, D2O rhodamine/Ge); and (3) at metal or semiconductor clusters deposited on sensor surface during the adsorption of detecting molecules (CO.Rh/SnO2 Pd/SnO2).

THE PARTICIPATION OF EXCITED OXYGEN IN A CHEMILUMINESCENT REACTION†

Abstract— Some properties of silica gel adsorbates of the acridine dye, acriflavine, have been investigated in the presence of oxygen and inert gases. In addition to its well‐known quenching of phosphorescence, oxygen stimulates additional luminescence, a chemi‐luminescence, at high concentrations of the dye triplet state molecules. The dependence of the chemiluminescence and of oxygen consumption on experimental variables have been explained in terms of a mechanism in which O2*, formed in the act of quenching of one photoexcited dye molecule by oxygen, diffuses to a second excited dye molecule where it may cause an irreversible oxidation. This oxidation may be accompanied by chemi‐luminescence. Both the intensity of the chemiluminescence and the rate of oxygen consumption were found to be reduced specifically by inert gases having vibrational frequencies close to the vibrational spacings of oxygen. It was concluded that O2* is probably vibrationally excited oxygen and that it is deactivated principally by resonance energy transfer processes.

Effect of promoters in hydrogenolysis of xylite

The equilibrium electrophysical parameters (electroconductivity work function) of semiconductor gas sensor surfaces are insufficient for the characterization of adsorption selectivity. The energy spectrum of surface electron states corresponding to the gas and vapour adsorption is quasicontinuous and does not reflect the individual properties of detecting molecules properly. Some types of vibronic (electron–vibrational) interactions arising in adsorption charging of the sensor surface are proposed to produce selectivity. Some vibronic effects are examined in the following situations: (1) At the adsorption of excited gas molecules (Ov=12, Zn/ZnO); (2) at the vibrational excitation of detecting molecules in deactivation events of previously adsorbed photoexcited dye molecules (H2O, D2O rhodamine/Ge); and (3) at metal or semiconductor clusters deposited on sensor surface during the adsorption of detecting molecules (CO.Rh/SnO2 Pd/SnO2).

Grafting onto cellulose and cellulose derivatives using ultraviolet irradiation

The cellulose-tendering properties of anthraquinone-2,7-disulfonic acid disodium salt have been successfully applied to graft various vinyl monomers onto cellulosic materials. A cellophane (or cellulose derivative) film is suspended in a solution containing monomer, solvent, dye, and water and irradiated with a 100-w. AH-4 mercury-vapor lamp. The photoexcited dye molecule abstracts a hydrogen atom from the substrate. The radical formed on the cellulose backbone initiates vinyl polymerization and a graft polymer is formed. The grafted film may be up to three and one-half times as heavy as the original substrate and has entirely different solubility characteristics. The degree of grafting is dependent on the monomer concentration in the solution and on the irradiation time. Maximum grafting is usually obtained employing a 24 hour irradiation period. The grafting is always accompanied by homopolymerization, which is not inhibited by atmospheric oxygen, but bubbling air through the solution will completely inhibit both the homopolymerization and the grafting. Substantial grafting can be obtained employing the following monomer-solvent systems: acrylonitrile-N,N-dimethylformamide; acrylamide-water; styrene-acrylonitrile-N,N-dimethylformamide. Good evidence for grafting has been obtained by comparing the solubility characteristics of the graft with those of a physical mixture of the cellulose and the homopolymer.