Photo- and electroluminescence of new organic semiconductors

The results of investigation of the luminescence under photo- and electroexcitation for four new compounds are presented. The spectral properties and photoluminescence are studied in ethanol, chloroform solutions and in films formed by thermovacuum deposition (TVD). The phosphorescence of compounds is investigated in ethanol at 77K temperature. The phosphorescence times of molecules are given. The electroluminescence is obtained in multilayered structure ITO/PEDOT/NPD/L /Ca/Al. It is shown, that spectral region of the photoluminescence of TVD films and electroluminescence coincide. Relations of electroluminescence efficiency with molecule structure, photoluminescence quantum yield and possibility of thermally activated delayed fluorescence are discussed

High-frequency homogenization for periodic media

This article is available open access through the publisher’s website at the link below. Copyright @ 2010 The Royal Society.An asymptotic procedure based upon a two-scale approach is developed for wave propagation in a doubly periodic inhomogeneous medium with a characteristic length scale of microstructure far less than that of the macrostructure. In periodic media, there are frequencies for which standing waves, periodic with the period or double period of the cell, on the microscale emerge. These frequencies do not belong to the low-frequency range of validity covered by the classical homogenization theory, which motivates our use of the term ‘high-frequency homogenization’ when perturbing about these standing waves. The resulting long-wave equations are deduced only explicitly dependent upon the macroscale, with the microscale represented by integral quantities. These equations accurately reproduce the behaviour of the Bloch mode spectrum near the edges of the Brillouin zone, hence yielding an explicit way for homogenizing periodic media in the vicinity of ‘cell resonances’. The similarity of such model equations to high-frequency long wavelength asymptotics, for homogeneous acoustic and elastic waveguides, valid in the vicinities of thickness resonances is emphasized. Several illustrative examples are considered and show the efficacy of the developed techniques.NSERC (Canada) and the EPSRC

Expression of NES-hTERT in Cancer Cells Delays Cell Cycle Progression and Increases Sensitivity to Genotoxic Stress

Telomerase is a reverse transcriptase associated with cellular immortality through telomere maintenance. This enzyme is activated in 90% of human cancers, and inhibitors of telomerase are currently in clinical trials to counteract tumor growth. Many aspects of telomerase biology have been investigated for therapy, particularly inhibition of the enzyme, but little was done regarding its subcellular shuttling. We have recently shown that mutations in the nuclear export signal of hTERT, the catalytic component of telomerase, led to a mutant (NES-hTERT) that failed to immortalize cells despite nuclear localization and catalytic activity. Expression of NES-hTERT in primary fibroblast resulted in telomere-based premature senescence and mitochondrial dysfunction. Here we show that expression of NES-hTERT in LNCaP, SQ20B and HeLa cells rapidly and significantly decreases their proliferation rate and ability to form colonies in soft agar while not interfering with endogenous telomerase activity. The cancer cells showed increased DNA damage at telomeric and extra-telomeric sites, and became sensitive to ionizing radiation and hydrogen peroxide exposures. Our data show that expression of NES-hTERT efficiently counteracts cancer cell growth in vitro in at least two different ways, and suggest manipulation with the NES of hTERT or its subcellular shuttling as a new strategy for cancer treatment

Infrared optical properties of the new organic conductors family (ET)8_8[ Hg2_2X6_6(C6_6H5_5Y)] 2_2 (X, Y = Cl, Br)

The polarized reflectivity spectra of the single crystals of three organic conductors (ET)$_8$[ Hg$_2$X$_6$(C$_6$H$_5$Y)] $_2$ (X, Y = Cl, Br) have been studied. The electronic IR band with a plasma edge is observed in the spectra similar to most conducting ET compounds. However, a group of the electron-vibrational bands usual for other ET salts is not observed which has been accounted for by the peculiarities of crystal structure due to which the vibrational modes responsible for electron-vibrational interaction belong to non-totally symmetric type

Electrochemical Properties and Absorption Spectra of Conducting Films of Tetrathyotetracene Iodids

Films of tetrathyotetracene (TTT) iodides were obtained by doping of evaporated TTT films with iodine from I-containing solutions. TTT was evaporated onto a conducting substrate which then was used as an anode in KI solution. As a result of electrochemical reaction, iodine penetrated into the TTT film forming conducting TTT iodides. Cyclic voltamogrammes and absorption spectra show at least two stable forms of TTT-I$\text{}_{x}$, differing by iodine contents

ELECTROCHEMICAL PROPERTIES AND ABSORPTION SPECTRA OF CONDUCTING FILMS OF TETRATHYOTETRACENE IODIDS

Films of tetrathyotetracene (TTT) iodides were obtained by doping of evaporated TTT films with iodine from I-containing solutions. TTT was evaporated onto a conducting substrate which then was used as an anode in KI solution. As a result of electrochemical reaction, iodine penetrated into the TTT film forming conducting TTT iodides. Cyclic voltamogrammes and absorption spectra show at least two stable forms of TTT-I x , differing by iodine contents

Different Types of Electron-Vibrational Interaction in BEDT-TTF Salts with Halide-Mercurate Anions Studied by IR Spectroscopy

Infrared optical properties of a large family of BEDT-TTF salts with mercury-halide anions are studied which exhibit different types of electron-vibrational spectra

Optical properties of organic conductor (ET)4_4Hg3_3I8_8 : alternative type of electron-vibrational interaction

The reflectivity spectra of single crystals of (ET)$_4$Hg$_3$I$_8$ and (d$_8$-ET)$_4$Hg$_3$I$_8$ were studied. In contrant with earlier studied clorine- and brominemercurate compounds of the series (ET)$_4$Hg$_{3 - \delta}$ - X$_8$ (X = Cl, Br, I), the spectra of iodinemercurate compounds exhibit low reflectivity without well-defined plasma edge and without electron-vibrational bands in the region 1 000 - 1 400 cm$^{-1}$. The latter fact may be due to electron-vibrational interaction with non-totally symmetric modes which may originate from peculiarities of crystal structure of iodinemercurate compounds. A phase transition of the first type is observed both for (ET)$_4$Hg$_3$I$_8$ and (d$_8$-ET)$_4$Hg$_3$I$_8$. At the transition temperature a jump in conductivity and reflectivity is observed