摘要:

Transient photocurrent measurements on LTQUIN, a good photoconductor in the wavelength region between 200 and 600 nm, show an anomalous behaviour with respect to other organic photoconductors. Photoconductive action spectra are also reported.

ISSN:1058-725X    

DOI:10.1080/10587259208025830

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This paper summarises recent progress in understanding the processes which lead to large increases in the semiconductivity of metal phthalocyanine films in the presence of even very small (sub-ppm) concentrations of nitrogen dioxide. A model, based on experimental data, for the kinetics of the adsorption process is described and its application in a microprocessor-controlled NO2-sensing instrument is outlined. Chemical and morphological modification of the surfaces of lead phthalocyanine films by heat-treatment at 360° C in air is shown to lead to smaller but faster responses to NO2and possible origins of these effects are discussed with reference to data from electron microscopy, XPS and FTIR spectroscopy. Measurements of the strength of gas-surface interactions using a novel fibre-optic interferometric calorimeter are discussed with reference to the above data, and suggest that adsorption of NO2does not lead immediately to charge-carrier generation.

ISSN:1058-725X    

DOI:10.1080/10587259208025831

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Significant modifications of the powder infrared spectra of TCNQ-based crystalline salts and composites, simply induced by deuteration of TCNQ, are presented and discussed.

ISSN:1058-725X    

DOI:10.1080/10587259208025832

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

When 3-methylthiophene is electropolymerized on a Nuclepore covered electrode in a propylene carbonate solution containing tetrabutylammonium hexafluorophosphate, braided and helical fibrils are formed. When the electrodes are arranged horizontally with the working electrode on top, greater morphological control is achieved, and the resulting helical fibrils show increased crystallinity and a much higher conductivity than fibrils prepared in the normal manner with vertically arranged electrodes. The conductivity is temperature independent from 15 K to room temperature.

ISSN:1058-725X    

DOI:10.1080/10587259208025833

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A new convenient synthesis of the diacetylenic nitroxide 4, 4′-(butadiyne-1, 4-diyl)-bis-(212, 6, 6-tetramethyl-4-hydroxypiperidin-l-oxyl) (1) has been achieved by oxidative coupling of the relevant monoacetylene. In the presence of air, polycrystalline samples of the beta phase of1are converted to the alpha polymorph on exposure to radiation from Cu Kα or60Co sources. This polymorphic transformation is conveniently monitored by observing the x-ray powder diffraction pattern in the 2θ range 6 –13°. New synthetic procedures to the diacetylenic nitroxides 2, 4-hexadiyn-l, 6-diyl-bis-(2, 2, 5, 5-tetramethyl-l-oxyl-3-pyrolline-3-carboxylate) (3) and 5-(2, 2, 6, 6-tetramethyl-l-oxyl-l, 2, 5, 6-tetrahydropyridin-4-yl)penta-2, 4-diyn-l-ol (4) are reported.

ISSN:1058-725X    

DOI:10.1080/10587259208025834

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Mixing propynoic acid and 4-(l-pyrrolidino)-pyridine in ethanol produces the salt 4-(l-pyrrolidino)-pyridinium propynoate (1) in high yield. An X-ray structure determination of1(Space GroupP2I, Z=4) shows it to contain two independent cation-anion sets. Each set is interconnected by N-H-0 and C-H-O hydrogen bonds; there are no hydrogen bonds formed between the two sets. Each set contains an infinite array of short acetylene-acetylene contacts (3.57 and 3.74 Å, respectively); despite this characteristic, the material does not polymerize upon exposure to60Co γ-rays. Heating1at 125 °C for 23 hours converts it, in high yield, to a 19:1 mixture of (Eand Z)-4-(l-pyrrolidino)-pyridinium-l-acrylate. To the best of our knowledge, this is the first example of the addition of a pyridine moiety to an acetylene in the solid state.

ISSN:1058-725X    

DOI:10.1080/10587259208025835

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We report the first picosecond photon echo measurements on a molecular solid in a high pressure diamond anvil cell at low temperature. We also present time-resolved coherent Raman measurements of vibrational relaxation in pure molecular crystals as a function of pressure in a diamond anvil cell at low temperature. Since photon echo spectroscopy eliminates inhomogeneous dephasing, we utilize this technique to yield the homogeneous dephasing rate for high pressure samples where sample inhomogeneities and inhomogeneous pressure gradients may exist. Since the Fourier transform of the photon echo decay yields the absorption lineshape, these experiments provide a means of obtaining high resolution spectra under extreme high pressure conditions. In addition, pressure induced changes in vibrational relaxation rates observed by picosecond coherent Raman measurements are used as a sensitive probe of the intermolecular interactions that give rise to relaxation phenomena.

ISSN:1058-725X    

DOI:10.1080/10587259208025836

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The centrosymmetric molecule, dianthracene, has four low-lying excited singlet states arising due to interactions between the four equivalent benzene chromophores in the molecule. An empirical model identifies the lowest excited state as1B3gwith the other three states at increasingly higher energies being1B1u,1B2u, and1Ag. The energy gap between the low temperature emission and fluorescence excitation spectra of crystalline dianthracene as well as the shape of the origin absorption spectrum and the lack of site-selected spectra in this region for dianthracene in a low temperature polymer host provide strong support for this predicted state ordering. The temperature dependence of the quantum yield for photodissociation of the dianthracene molecule and the emission spectrum of the anthracene pairs formed by this reaction are also presented.

ISSN:1058-725X    

DOI:10.1080/10587259208025837

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The presence of C3πu→ B3πgemissions of dinitrogen and photoluminescence in triboluminescence spectra provides information about the mechanism of light production.

ISSN:1058-725X    

DOI:10.1080/10587259208025838

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

In order to study the solid phase struc ture effects upon mechanism of photochromic trans formations in 4,4′-bipyridine quaternary salt se ries new photochromic substances have been synthe sized and their photochromic properties studied in single crystals. X-ray studies have been carried out, and effects of molecular and crystal structu re of the substances in the ground state upon their photochromic properties were considered. Differen ces in molecular stacking have been found out for molecules with different photochemical properties.

ISSN:1058-725X    

DOI:10.1080/10587259208025839

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor