Morphology of sulphur-terminated compound deposits condensed on different substrates in vacuum

Thin films of new sulphur-terminated organic compounds were deposited by evaporation in vacuum onto the glass, silicone, gold and polytetrafluoroethylene substrates. The influence of compound chemical structure and substrate type on morphology of the condensed solid was studied using atomic force microscopy. The significant difference in morphology of the same dye but deposited on various substrates was found

Enhancement of optical and magneto-optical effects in three-dimensional opal/Fe3O4 magnetic photonic crystals (vol 93,art no 072502, 2008)

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PEPC sensitization with polymethine dyes: 1. Squarylium dyes of indole row as efficient sensitizers for red region of optical spectrum

Phase hologram recording is based on photoconductivity which appears in polymer molecular semiconductor film being exposed to light [1]. Photocurrent threshold depends on energy gap between valence and conduction bands of a photoconductor (PC). Energy gap of PCs based on poly-N-epoxypropylcarbazole (PEPC) which are widely used for hologram recording is rather large. That is why recording on pure PEPC film may be only in UV range of optical spectra. Thus, sensitization of PEPC with different dyes to make it sensitive to visible range is usually used for practice. Nowadays structural PEPC sensitization with fluorene electron acceptors is widely used for holographic recording material synthesis [2]. There are few publications about organic dye sensitization of PEPC due to low efficiency of first dyes used. Main obstacle to practical use of dyes like rhodamine 6G, malachite green and other 3-phenilmethans, is low diffraction efficiency (η) of hologram due to large charges thermo-relaxation in single-layer PEPC films. We have investigated some polymethine dyes like squarylium with indole residues for PEPC sensitization in red range of visible spectrum. These dyes are under intense interest due to its promising usefulness for xerography and optical recording. Particularity of such dyes is its intra-ionoide, actually bipolar, structure

Suppression of Kasha’s rule in higher excited states of 4-pyrilocyanines

Spectral properties of the series of cationic polymethine dyes containing conjugated chain of different length and 4-pyrylium terminal groups were studied in details. Besides, the steady-state long-wavelength fluorescence from the lowest excited state and the fluorescence from higher excited states were experimentally revealed. The steady-state fluorescence band from the lowest excited state is shifted bathochromically with lengthening of the polymethine chain, which is also reflected in the absorption shift. According to quantum-chemical modeling, the appearance of unconventional fluorescence, which suppresses Kasha’s rule, is associated with the different nature of the lowest excited states: the first and forth transitions are typical polymethine electron transitions involved only totally delocalized molecular orbitals (MOs), whereas the second and third transitions correspond to the electron jumping from the degenerated MOs localized only within the terminal groups (so called quasi-local MOs and hence quasi-local transitions). The forbidden transitions between the excited states of different types stimulate the fluorescence from the higher excited states