Influence Of Photoisomerization Research Articles

Tetra-azobenzene extended calix[4]pyrroles: influence of photo-isomerization on chloride binding and its transport through liposomal membranes

Photo-modulation in chloride binding affinity and transmembrane transport with tetra-azobenzene extended calix[4]pyrroles.

Influence of Photoisomerization on Binding Energy and Conformation of Azobenzene-Containing Host-Guest Complex

Influence of Photoisomerization on Binding Energy and Conformation of Azobenzene-Containing Host-Guest Complex

Holographic recording in photochrome-chalcogenide composites

The method of preparation of thin triple composite films of organic polymer-chalcogenide-photochromes is described, and some features of photo induced changes of optical properties and holographic recording in this system are studied. Films of composite were obtained from solutions of arsenic sulphide and organic polymers, such as “Disperbyk” (produced by BYK-Chemie GmbH) and polyvinylacetate in organic solvents. The azobenzene DR-1 and spiropyran solutions were added in this mixture. The films were obtained by casting the material on glass or quartz substrate. The dry film thickness was in the range of 3–10 μm. The changes of absorption spectra of the films induced by UV (248, 325, and 375 nm) laser light were studied and analysed. The holographic recording of diffraction gratings was performed by different laser lines (325, 442, and 532 nm). During recording the diffraction efficiency was measured simultaneously in transmission and reflection mode. The formation of relief on the film surface was observed and the profile of the gratings was analysed by atomic force microscope. The influence of photoisomerization and photo induced mass transport on the surface-relief formation process has been discussed. Keywords: arsenic sulphide, Disperse Red 1, spiropyran, polymer-photochrome composite, polymer-photochrome-chalcogenide composite, holographic grating

Formation of Direct Surface Relief in Photochrome-Chalcogenide Composites

Formation of Direct Surface Relief in Photochrome-Chalcogenide CompositesA method for preparation of thin triple composite films of organic polymer-chalcogenide-photochromes is described, the photo-induced changes of optical properties and holographic recording are considered. The films were obtained from solutions of arsenic sulphide, azobenzene Disperse Red 1, spiropyran, and organic polymers in organic solvents. The solutions were spread over glass or quartz substrates; the thickness of dry films was 3-10 μm. The absorption spectra of the prepared films were studied and analyzed. The holographic recording of diffraction gratings was performed by laser lines of 325 nm, 442 nm and 532 nm. During recording the diffraction efficiency was measured simultaneously in the transmission and reflection modes. The relief formation on the film surface was observed and the profile of the gratings formed was analyzed using AFM microscope. The influence of photoisomerization and photo-induced mass transport on the surface relief formation process is discussed.

Influence of photoisomerization on photoprocesses in molecules with a styryl group

A quantum-chemical study of the influence of the photoisomerization reaction on the efficiency of the processes of decay of the fluorescent state of a molecule of a model compound containing a styryl group is performed. The influence of variations in the structural parameters and the geometry of the model molecule on the positions of low-lying electronic states and the efficiency of degradation of the fluorescent state is studied. It is shown that the best agreement between the results of calculations and the experimental data is obtained when a linear butadiene model is used.

High-performance polysiloxane-based photorefractive polymers with nonlinear optical azo, stilbene, and tolane chromophores

The performance of photorefractive (PR) polymers strongly depends on the incorporated nonlinear-optical chromophores. We compare three polysiloxane-based PR guest–host polymers with an azo, a stilbene, and a tolane type of chromophore. Characteristic properties such as diffraction efficiency η, gain coefficient Γ, phase shift ϕ, modulation of the index of refraction Δn, and response time are measured as a function of the external electric field. Orientational enhancement as well as the influence of photoisomerization is observed and analyzed quantitatively. The materials show high performance with Δn>1×10-2, corresponding to external diffraction efficiencies of 60% for samples of only 40-μm thickness.

Influence of photoisomerization on saturated absorption of 3,3′-diethyloxadicarbocyanine iodide (DODCI) studied by diffraction from laser-induced, anharmonic thermal gratings

Saturated optical absorption of 3,3′-diethyloxadicarbocyanine iodide (DODCI) in alcohol solvents has been studied using the laser-induced anharmonic thermal grating technique. The probe angle dependence of diffraction intensity is resolved into two Gaussian profiles, centered at first and second Bragg incidence, respectively. The diffraction transients observed at these angles have time dependences described by single exponentials with a 1: 1 4 ratio of time constants, in agreement with thermal relaxation of an anharmonic Bragg grating. The excitation intensity dependence of the diffraction signals is interpreted using Rullière's kinetic model with an assumption that the non-radiative transition of the excited photoisomer proceeds mainly via internal conversion. A set of kinetic equations for Rullière's model has been solved numerically to describe the time evolution of the populations of all levels under a step pulse excitation. The weaker absorption by the photoisomer and reverse-photoisomerization have made the effective saturation intensity of DODCI very large in comparison with the predictions of a simple three-level model. The absorption cross section of DODCI photoisomer in ethanol is estimated from this work to be (4.7 ± 0.2) × 10 −18 cm 2 (at 532 nm), the back-photoisomerization yield is 0.017 ± 0.005 in methanol, and an upper limit to the photoisomer excited state lifetime is 1.3 ± 0.3 ns in ethylene glycol.

Superluminescence and stimulated emission from unstable photoisomers of polymethine dyes

The criteria governing the superluminescence and stimulated emission from unstable photoisomers of polymethine dyes are studied for the first ime. It is shown that this is an important factor in stimulated emission from polymethines under conditions of anti-Stokes pumping of initial stable molecule solutions. Numerical calculations are made of the gain spectra of polymethine solutions containing photoisomers pumped by radiation of varying spectral composition. Conclusions are drawn on the influence of photoisomerization on the stimulated emission characteristics of these media under different pumping conditions.