110 research outputs found
In situ determination of the energy dependence of the high-frequency mobility in polymers
The high-frequency mobility in disordered systems is governed by transport
properties on mesoscopic length scales, which makes it a sensitive probe for
the amount of local order. Here we present a method to measure the energy
dependence of the high frequency mobility by combining an electrochemically
gated transistor with in-situ quasi-optical measurements in the sub-terahertz
domain. We apply this method to
poly([2-methoxy-5-(3',7'-dimethylocyloxy)]-p-phenylene vinylene) (OC_1C_10-PPV)
and find a mobility at least as high as 0.1 cm^2V^-1s^-1.Comment: 3 pages (incl. 3 figures) in Appl. Phys. Let
Tunable Frohlich Polarons in Organic Single-Crystal Transistors
In organic field effect transistors (FETs), charges move near the surface of
an organic semiconductor, at the interface with a dielectric. In the past, the
nature of the microscopic motion of charge carriers -that determines the device
performance- has been related to the quality of the organic semiconductor.
Recently, it has been appreciated that also the nearby dielectric has an
unexpectedly strong influence. The mechanisms responsible for this influence
are not understood. To investigate these mechanisms we have studied transport
through organic single crystal FETs with different gate insulators. We find
that the temperature dependence of the mobility evolves from metallic-like to
insulating-like with increasing the dielectric constant of the insulator. The
phenomenon is accounted for by a two-dimensional Frohlich polaron model that
quantitatively describes our observations and shows that increasing the
dielectric polarizability results in a crossover from the weak to the strong
polaronic coupling regime
Greener Method to Obtain a Key Intermediate of Vitamin E over Cu-ZSM-5
The catalytic oxidation of 2,3,5-trimethylphenol was performed over transition metals modified ZSM-5 zeolites employing hydrogen peroxide as oxidant under mild reaction conditions. Catalysts samples were characterized by several techniques (XRD, FTIR, BET, AA) and cristallinity and orthorhombic symmetry were confirmed for all of them. Best catalytic results were obtained for Cu-ZSM-5 sample, so further activity studies were done over this material. 2,3,5-trimethyl-1,4-benzoquinone was obtained as the main product of the selective oxidation. Reaction parameters (nature of the solvent, hydrogen peroxide concentration, reaction time, catalyst mass, substrate initial concentration and reaction temperature) were evaluated to reach the optimum reaction conditions. According to the obtained results, an apparent activation energy of 52.33 kJ/mol was calculated.Fil: Saux, Clara. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Cordoba. Centro de Investigacion y Tecnologia Quimica; Argentina. Universidad Tecnologica Nacional. Facultad Regional Cordoba; ArgentinaFil: Renzini, Maria Soledad. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Cordoba. Centro de Investigacion y Tecnologia Quimica; Argentina. Universidad Tecnologica Nacional. Facultad Regional Cordoba; ArgentinaFil: Gómez, Silvina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Cordoba. Centro de Investigacion y Tecnologia Quimica; Argentina. Universidad Tecnologica Nacional. Facultad Regional Cordoba; ArgentinaFil: Pierella, Liliana Beatriz. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Cordoba. Centro de Investigacion y Tecnologia Quimica; Argentina. Universidad Tecnologica Nacional. Facultad Regional Cordoba; Argentin
High Electron Mobility in Vacuum and Ambient for PDIF-CN2 Single-Crystal Transistors
We have investigated the electron mobility on field-effect transistors based
on PDIF-CN single crystals. The family of the small molecules
PDI8-CN has been chosen for the promising results obtained for
vapour-deposited thin film FETs. We used as gate dielectric a layer of PMMA
(spinned on top of the SiO), to reduce the possibility of electron
trapping by hydroxyl groups present at surface of the oxide. For these devices
we obtained a room temperature mobility of 6 cm/Vs in vacuum and 3
cm/Vs in air. Our measurements demonstrate the possibility to obtain
n-type OFETs with performances comparable to those of p-type devices.Comment: published online in JAC
Titanium dioxide doped with vanadium as effective catalyst for selective oxidation of diphenyl sulfide to diphenyl sulfonate
Solution-processed, Self-organized Organic Single Crystal Arrays with Controlled Crystal Orientation
A facile solution process for the fabrication of organic single crystal semiconductor devices which meets the demand for low-cost and large-area fabrication of high performance electronic devices is demonstrated. In this paper, we develop a bottom-up method which enables direct formation of organic semiconductor single crystals at selected locations with desired orientations. Here oriented growth of one-dimensional organic crystals is achieved by using self-assembly of organic molecules as the driving force to align these crystals in patterned regions. Based upon the self-organized organic single crystals, we fabricate organic field effect transistor arrays which exhibit an average field-effect mobility of 1.1 cm2V−1s−1. This method can be carried out under ambient atmosphere at room temperature, thus particularly promising for production of future plastic electronics
Heterogeneous sulfoxidation of thioethers by hydrogen peroxide over layered double hydroxides as catalysts
International audienceA new method for mild oxidation of thioethers with hydrogen peroxide in heterogeneous catalysis is described. The layered double hydroxides (or hydrotalcite-like materials) act as basic catalysts for the sulfoxidation reaction with hydrogen peroxide in the presence of acetonitrile. The influence of the nature of thioether, the type of catalyst, the reaction temperature and reaction time on the catalytic activity and selectivity in this reaction has been investigated. A mechanism of the sulfoxidation reaction is proposed. © 2001 Elsevier Science B.V
DETERMINATION OF MOLECULAR WIGHT OF ISOENZYMES IN A CRUDE EXTRACT BY THIN TAYER GEL FILTRATION AND POLYACRYLAMIDE GEL ELECTROPHORESIS
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