Electrosynthesis and comparative studies on carboxyl-functionalized polythiophene derivatives

Electrochemical synthesis of a novel carboxylic acid functionalized polythiophene – poly(3-thiophene-butyric-acid), PTBA – has been realized. Its morphology, electrochemical, spectral and conducting properties have been compared to those of poly(3-thiophene-acetic-acid), PTAA, which is widely used to immobilise both bioactive molecules and inorganic nanoparticles. According to scanning electron microscopic (SEM) images, the difference in the real and geometric surface area of the modified electrodes is much more expressed in the case of PTBA. Both the symmetry of the cyclic voltammograms and the concurrent, sustained optical changes proved that this polymer possesses an improved and more stable redox activity. According to simultaneously performed in situ ac. impedance and UV–Vis measurements, both films could be uniformly transformed between the insulating and conducting forms, but PTAA exhibited some degradation. The development of the conducting state during the redox switching of both thiophene derivative polymers proved to be primarily connected to the formation of di-cationic species. The electrochemical quartz crystal microbalance (EQCM) results evidenced also differences between the two polymers, which difference can be interpreted by assuming the more expressed effect of the deprotonation-connected (self-) doping process in PTAA. The results confirm that the new conducting polymer, PTBA is much more convenient for being considered as the polymer matrix of practically applicable composites.     

Modelling of interactive populations of disperse systems

The paper presents a general mathematical model for disperse systems in which direct interactions between particles are taken into consideration. The model is formulated in terms of transition measures, introduced on the basis of conditional Markov processes. The population balance equation, describing the behaviour of interactive populations, is developed in a general form of continuous and discontinuous terms. Moment equations are presented and analysed for the axial dispersion model with interparticle exchange processes of heat and mass. The applicability of the model is illustrated by applying it for describing a process of heating particles by gas with interparticle heat transfer, and a mass exchange process between fluid particles.     

Study of defect levels in CdTe using thermoelectric effect spectroscopy

We have studied the defect levels in as grown and post growth processed cadmium telluride (CdTe) using thermoelectric effect spectroscopy (TEES) and thermally stimulated current (TSC) techniques. We have extracted the thermal energy (E_th) and trapping cross section (σ_th) for the defect levels using the initial rise and variable heating rate methods. We have identified 10 different defect levels in the crystals. Thermal ionization energy values obtained experimentally were compared to theoretical values of the transition-energy levels of intrinsic and extrinsic defects and defect complexes in CdTe determined by first-principles band-structure calculations. On the basis of this comparison, we have associated the observed ionization levels with various native defects and impurity complexes.     

Testosterone and progesterone level alterations in the adult rat after retinoid (retinol or retinoic acid) treatment (imprinting) in neonatal or adolescent age

Newborn rats were treated with a single dose of vitamin A (retinol), or with three doses of retinoic acid (in the 1st, 3rd and 5th days). Serum testosterone and progesterone level was measured in the four months old male and female rats, respectively. Retinol significantly decreased both hormone levels, however retinoic acid decreased the progesterone level only. In the second part of the experiments adolescent rats (in the 6th and 7th week after birth) were treated and measured similar to the newborns. In this case retinol significantly diminished testosterone level, without influencing the progesterone level. Retinoic acid decreased testosterone level and elevated progesterone level. The results demonstrate the long lasting effects of retinoid treatments at a neonatal or adolescent age, pointing also to the differences in the direction of the effects. Considering that previously the receptorial and sexual-behavioral effects of perinatal vitamin A treatments were observed, the experiments call attention to such harmful influences of perinatal vitamin A treatments, which are not manifested in morphological alterations.     

Development of the high-pressure electro-dynamic gradient crystal-growth technology for semi-insulating CdZnTe growth for radiation detector applications

The high-pressure electro-dynamic gradient (HP-EDG) crystal-growth technology has been recently developed and introduced at eV PRODUCTS to grow large-volume, semi-insulating (SI) CdZnTe single crystals for room-temperature x-ray and gamma-ray detector applications. The new HP growth technology significantly improves the downstream CdZnTe device-fabrication yield compared to earlier versions of the HP crystal-growth technology because of the improved structural and charge-transport properties of the CdZnTe ingots. The new state-of-the-art, HP-EDG crystal-growth systems offer exceptional flexibility and thermal and mechanical stability and allow the growth of high-purity CdZnTe ingots. The flexibility of the multi-zone heater system allows the dynamic control of heat flow to optimize the growth-interface shape during crystallization. This flexibility combined with an advanced control system, improved system diagnostics, and realistic heat-transport modeling provides an excellent platform for continuing process development. Initial results on large-diameter (140 mm), SI Cd_1−xZn_xTe (x=0.1) ingots grown in low temperature gradients with the HP-EDG technique show reduced defect density and complete elimination of ingot cracking. The increased single-crystal yield combined with the improved charge transport allows the fabrication of large-volume, high-sensitivity, high energy-resolution detector devices at increased yield. The CdZnTe ingots grown to date produced large-volume crystals (≥1cm³) with electron mobility-lifetime product (μτ_e) in the (3–7) × 10⁻³ cm²/V range. The lower-than-desired charge-transport uniformity of the HP-EDG CdZnTe ingots is associated with the high density of Te inclusions formed in the ingots during crystallization. The latest process-development efforts show a reduction in the Te-inclusion density, an increase of the charge-transport uniformity, and improved energy resolution of the large-volume detectors fabricated from these crystals.     

Incorporation of single-wall carbon nanotubes into an organic polymer monolithic stationary phase for mu-HPLC and capillary electrochromatography

Single-wall carbon nanotubes (SWNT) were incorporated into an organic polymer monolith containing vinylbenzyl chloride (VBC) and ethylene dimethacrylate (EDMA) to form a novel monolithic stationary phase for high-performance liquid chromatography (HPLC) and capillary electrochromatography (CEC). The retention behavior of neutral compounds on this poly(VBC-EDMA-SWNT) monolith was examined by separating a mixture of small organic molecules using micro-HPLC. The result indicated that incorporation of SWNT enhanced chromatographic retention of small neutral molecules in reversed-phase HPLC presumably because of their strongly hydrophobic characteristics. The stationary phase was formed inside a fused-silica capillary whose lumen was coated with covalently bound polyethyleneimine (PEI). The annular electroosmotic flow (EOF) generated by the PEI coating allowed peptide separation by CEC in the counterdirectional mode. Comparison of peptide separations on poly(VBC-EDMA-SWNT) and on poly(VBC-EDMA) with annular EOF generation revealed that the incorporation of SWNT into the monolithic stationary phase improved peak efficiency and influenced chromatographic retention. The structures of pretreated SWNT and poly(VBC-EDMA-SWNT) monolith were examined by high-resolution transmission electron microscopy, Raman spectroscopy, scanning electron microscopy, and multipoint BET nitrogen adsorption/desorption.     

Influence of water content on the product distribution in the electrochemical chlorination of c-hexene in nitromethane

Effect of water content on product distribution in electrochemical chlorination of c-hexene in nitromethane solution was studied. Formation of 1-chloro, c-hexanone which occurs at the beginning of electrolysis is more effective at lower water content.