Infrared Spectra and Photoinduced Absorption of C60 Doped Polyhexylthiophene

Abstract

We report the IR spectra and the photoinduced absorption of polyhexylthiophene(PHT) doped with C₆₀. The presence of C₆₀ ^?n anions is observed in the IR spectra by a mode at 1383 cm^?1 and a broad electronic transition at 1.2 eV, while most of the C₆₀ molecules stay neutral. This is indicative that for a small fraction of C₆₀ molecules, charge transfer occurs in the ground state.

The photoinduced absorption spectra display a sharp transition at 1.15 eV peculiar to C₆₀ monoanion, the spectral features change with fullerene concentration. The intensity of the polymer photoinduced bands increases 5-10 times due to photoinduced charge transfer to C₆₀.     

Electro-optic behavior of liquid-crystal-filled silica opal photonic crystals: effect of liquid-crystal alignment

Photonic crystals made of nematic liquid crystal intercalated into the void space of close-packed silica spheres (synthetic porous opal) exhibit significant electric-field-induced shift of the optical Bragg reflection peak when the liquid crystal has the long molecular axis oriented parallel to the sphere surfaces. No such effect is observed for comparable fields when the long-axis orientation is normal to the sphere surfaces.     

Spectroscopic study of bleaching of some cyanine dyes in solution and in polyvinyl alcohol films

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 48, No. 4, pp. 601–604, April, 1988.     

Association of bi-cyanine dyes with rigidly linked chromophores in polar solvents

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 50, No. 2, pp. 237–243, February, 1989.     

Field emission of electrons by carbon nanotube twist-yarns

Field emission with high current density at low operating voltage was found for the yarns obtained by solid state spinning process from forest of vertically aligned multiwall carbon nanotubes. The nanotube forest was produced catalytically by CVD method. It is found that only a small fraction of carbon nanotubes from their total amount in the yarn yields to electron emission from its free end. This led to resistive heating of the emitting tubes and limiting of the emission current. The field emission microscopy pictures of MWNT yarn in free-end geometry appears to be very different from that of the conventional non-yarn carbon nanotube-based cathodes described in all previous studies. The FEM patterns are found to consist of the set of line and arc segments rather than a set of spots. Possible explanation of this effect is presented and discussed. The field emission from the lateral side of the yarns showed the self-enhanced currents increasing with operation time. We assume that this current increase may be due to untwisting and unwrapping of yarns resulted of application of the electric field. The lowest threshold field of about 0.7 V/μm was obtained after a few cycles of applied field increase. The prototypes of cathodoluminescent lamps and alphanumerical indicators based on MWNT twist-yarn cold cathodes are demonstrated. PACS 79.70.+q; 61.46.Fg; 85.45.Db     

Charge-induced anisotropic distortions of semiconducting and metallic carbon nanotubes

To accommodate extra electrons or holes injected into a single-wall carbon nanotube, carbon-carbon bonds adjust their lengths. Resulting changes in carbon-nanotube length as a function of charge injection provide the basis for electromechanical actuators. We show that a key mechanism at low injection levels, modulation of electron kinetic energy, provides nanotube deformations that are both anisotropic and strongly dependent on nanotube structure. Nanotubes can exhibit both expansion and contraction, as well as nonmonotonic size changes. The magnitude of the actuation response of semiconducting carbon nanotubes may be substantially larger than that of graphite.     

Raman spectroscopy of the interface between a thin nanostructured ZnO film and fullerene C60

The resonance and nonresonance Raman scattering in the interface between a thin ZnO film with a well-developed nanostructured surface morphology and a layer of fullerene C60 molecules deposited on this film has been investigated. It is shown that the intensity of the interaction between the C60 molecules and ZnO film surface can be estimated based on the spectral scattering characteristics.