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Subpicosecond fluorescence anisotropy decay curves have been measured using the fluorescence up-conversion technique to examine the rotational dynamics of coumarin 153 (C 153) in supercritical fluoroform (T = 302 and 310 K). For reduced densities (p, = ρ/ρ c ) above 0.9, the rotation times of C153 increase with density. For reduced densities lower than 0.9, the rotation times increase with decreasing density and has a maximum at a density near p, = 0.5. The comparison with the extrapolation of the data in polar aprotic solvents indicates that the local solvent density around the solute exceeds about 4 times the bulk density at a density near ρ r = 0.5, which is consistent with those obtained from the steady-state electronic spectral shifts.

The layer-by-layer alternate assemblies incorporating two kinds of cyanine dyes have been fabricated by alternately adsorbing a cationic polyelectrolyte and anionic cyanine dyes on the quartz plate. A thiacyanine dye (dye I) was employed as the donor and two kinds of thiacarbocyanine dye having a meso-alkyl groupm-ethyl (dye II), m-methyl (dye III)as the acceptor. The mole fraction of the acceptor in the mixed J-aggregate, χ, was varied from 0 to 1. It is confirmed that these dye combinations form the mixed J-aggregate in the alternate assemblies. From steady-state fluorescence spectra of the molecular assemblies, excitation energy transfer from the donor J-aggregate to the acceptor J-aggregate is observed, whose kinetics obeys the Stern−Volmer relationship. The experimentally determined rate constant of energy transfer, kET, is fairly large, indicating efficient energy transfer due to exciton migration through the donor J-aggregate. The relative fluorescence quantum yield and the fluorescence lifetime of...

Au, Ag, and Au/Ag colloidal nanoparticles coated with the J-aggregate of an anionic cyanine dye, 3,3‘-disulfopropyl-5,5‘-dichlorothiacyanine sodium salt (TC), have been prepared for the first time. The absorption spectrum of TC-coated Au colloidal nanoparticles is not a simple sum of the contributions of colloidal gold and TC but is characterized by an evident absorption dip at the position corresponding to the J-band of TC. These spectral features are reproduced by the simulation based on the Maxwell−Garnett-type treatment of Gao et al. The alternate adsorption technique allowed us to deposit dye-coated Au/Ag composite nanoparticles at the surface of a cationic polymer, poly(diallyldimethylammonium chroride).

We incorporated the alkyl chain substituted spiropyran derivatives, 1-methyl-3,3-dimethyl-6‘-nitrospiro[indoline-2,2‘-[2H][1]benzopyran] (SP1), 1-octadecyl-3,3-dimethyl-6‘-nitrospiro[indoline-2,2‘-[2H][1]benzopyran] (SP18), and 1-octadecyl-3,3-dimethyl-6‘-nitro-8-[docosanoyloxymethyl]spiro[indoline-2,2‘-[2H][1]benzopyran] (SP1822) into the planar bilayer lipid membranes (BLM) of soybean lecithin for the first time, and the photoresponse of the BLM was monitored. When a dc voltage was applied across the BLM, the transmembrane current changed under alternate irradiation with ultraviolet light and visible light. Such a photoelectric response of the BLM seems to be caused by the change in the membrane conductivity due to photoisomerization of spiropyran.

Etude de l'adsorption de deux colorants cyaniniques sur des vesicules de dimyristoylphosphatidylcholine et de phosphate de dicetyl