Optical properties of dibenzo[d,d']thieno[3,2-b;4,5-b']dithiophene monocrystals: the effect of intermolecular interactions.

The polarized UV-visible absorption spectra of dibenzo[d,d']thieno[3,2-b;4,5-b']dithiophene single crystals are reported and interpreted to definitively attribute the observed bands and their polarizations. The results provide information on the intermolecular interactions and on the aggregation in the condensed phase, which can be of either herringbone- or H-type, depending on the electronic transition taken into considerations, with consequences on the order and polarization of the absorption bands. A relatively easy method is also discussed to obtain information on the structural/morphological properties of different types of samples, including thin films, which have been recently proposed for high-performance organic film-effect transistors for their high ionization potential and photostability.

Polarized absorption, spontaneous and stimulated blue light emission of J-type tetraphenylbutadiene monocrystals.

Blue amplified spontaneous emission at room temperature is demonstrated from the exposed face of the strongly emitting organic semiconductor 1,1,4,4-tetraphenyl-1,3-butadiene in single crystal form. The symmetry of the crystal and calculation of lattice sums indicate the J-type organization of the molecular transition moments. The minimum in the lowest exciton dispersion branch, from which emission takes place, is found at the edge of the Brillouin zone leading to a dominant vibronic emission since the zero-phonon line is forbidden.

Choline and phosphatidylcholine fluorescent derivatives localization in carcinoma cells studied by laser scanning confocal fluorescence microscopy.

In this study, we have shown the intracellular distribution of choline and phosphatidylcholine fluorescent derivatives in human breast carcinoma cells using confocal microscopy. The fluorescent choline derivatives ethanamimium 2-hydroxy-N,N-dimethyl-N-[2-N-(2,1,3-benzoxadiazol-4-amine,-N-methyl,-7- nitro)-ethyl] bromide (NBD-choline) and C(6)-NBD-phosphatidylcholine (C(6)-NBD-PC) were used in this work. NBD-choline was easily internalised into drug sensitive MCF-7 and in multidrug resistant MCF-7/DX cells.