Emission of a single conjugated polymer chain isolated in its single crystal monomer matrix

The excitonic luminescence of a highly ordered single conjugated polymer chain is studied by microphotoluminescence. At T< or =10 K it consists of a single Lorentzian line. The linewidth increases linearly with T between 6 and 60 K, from 350 microeV at 6 K, indicating a pure dephasing time of approximately 2 ps. Above 10 K, other neighboring regions along the chain direction start to emit at a slightly higher (by approximately 1 meV) energy. This indicates very small inhomogeneous broadening, very long chains ( > or =10 microm), and a long range and very rapid exciton energy transfer ( >10 microm in <100 ps).     

Continuous wine making by delignified cellulosic materials supported biocatalyst

The continuous making of wine by a delignified cellulosic (DC) material-supported biocatalyst is reported. It was prepared by immobilizing the alcohol resistant strain AXAZ-1 on DC material. The product was found suitable for the continuous process in industrial applications. The operational stability was maintained for 2 mo with monitoring the ethanol concentration, wine, and alcohol productivities as well as the stability of °Be density at the outlet. Wine productivity was three to sixfold higher than obtained by natural fermentation, alcohol concentrations of the wine was in the range of 9.3-211.2% v/v and low volatile acidities of 0.15-20.36 g acetic acid/L were obtained. The effect of total acidity and flow rate of must were also examined. To demonstrate that the operational stability of the bioreactor is due to DC material that promotes the fermentation, and it takes place at even higher ethanol levels, an analogous system of kissiris supported biocatalyst was studied. Likewise, the tolerance in the alcohol concentration, as compared with free cells, were studied by their stability of the activity in the repeated batch fermentation of must.     

Carrier scattering by Auger mechanism in a single quantum wire

We report on time-resolved microphotoluminescence experiments in a single GaAs/GaAlAs V-shaped quantum wire as a function of optical excitation intensity. At low pump power we observe that excitons are localized in quantum boxes formed by the local potential minima existing along the wire axis. As the pump power is increased, state filling of the lowest lying levels of the boxes appears. When two carriers occupy the first excited level of the box, a very efficient Auger scattering occurs, leading to a transfer of carriers from one box to another neighbouring one. The intradot Auger scattering time has been measured and is of the same order of magnitude as the LA-phonon emission rate. Received 5 February 2001     

Polymerization of oriented monomers. V. Radiation-induced polymerization of 3n-dodecyl-1-vinylimidazolium iodide in micellar aggregates

In the present study radiation-induced polymerization of 3n-dodecyl-1-vinylimidazolium iodide (I) in micellar aggregates was investigated. For comparison, the corresponding isotropic polymerization of I was also studied. Micellization was obtained in concentrated aqueous solutions; that is, above the monomer's critical micelle concentration (CMC) polymers obtained by both modes of polymerization were treated similarly and subsequently subjected to physical characterization. The main purpose of this study was to investigate whether the degree of organization of the monomer in micelles would affect polymer properties. Attempts to determine tacticity by ¹³C-NMR spectrometry failed because of the particular structure of the polymer. Crystallization of these polymers from ethyl alcohol or acetone was not possible as indicated by x-ray powder diffraction patterns that were characteristic of amorphous polymers. On the other hand, viscosity data of polymers do not depend on the mode of polymerization. It is therefore concluded that micellar aggregates are not sufficiently organized to affect polymer properties.