Probing the Activity of Iron Peroxo Porphyrin Intermediates in the Reaction Layer during the Electrochemical Reductive Activation of O2

Herein we report the first example of using scanning electrochemical microscopy (SECM) to quantitatively analyze O₂ reductive activation in organic media catalyzed by three different Fe porphyrins. For each porphyrin, SECM can provide in one single experiment the redox potential of various intermediates, the association constant of Fe^II with O₂, and the pK_a of the Fe^III(OOH^?)/ Fe^III(OO^2?) couple. The results obtained can contribute to a further understanding of the parameters controlling the catalytic efficiency of the Fe porphyrin towards O₂ activation and reduction.     

Development of Carbazole and Bipyridine Copolymers as Novel Photovoltaic Materials

Summary: A novel acrylate polymer with a carbazole pendant group and bipyridine derivatives as side chains was synthesized, in which derivatives of bipyridine as electro-optic chromophores and carbazole as photoconductive moiety were covalently linked to the acrylate backbone. 2–(Carbazol-9-yl)ethyl methacrylate (CEM) and methacrylic 2-[5-(2-{5,5′-dimethyl-6′-[2-(5-pentylthiophen-2-yl)vinyl]-3,3′-bipyridin-6-yl}vinyl)thiophen-2-yl]ethyl methacrylate (BiPy) were synthesized and then copolymerized to give 99:1, 98:2, 92:8 (mol/mol) CEM/BiPy copolymers. Films of the copolymers blended with poly(3-octylthiophene) (P3OT) or poly(3-decylthiophene) (PDT) and sandwiched between the transparent ITO and Al electrode were examined for photovoltaic properties.     

A mathematical model of aging-related and cortisol induced hippocampal dysfunction

Background  

The hippocampus is essential for declarative memory synthesis and is a core pathological substrate for Alzheimer's disease (AD), the most common aging-related dementing disease. Acute increases in plasma cortisol are associated with transient hippocampal inhibition and retrograde amnesia, while chronic cortisol elevation is associated with hippocampal atrophy. Thus, cortisol levels could be monitored and managed in older people, to decrease their risk of AD type hippocampal dysfunction. We generated an in silicomodel of the chronic effects of elevated plasma cortisol on hippocampal activity and atrophy, using the systems biology mark-up language (SBML). We further challenged the model with biologically based interventions to ascertain if cortisol associated hippocampal dysfunction could be abrogated.     

First examples of organophosphorus-containing materials for light-emitting diodes

Exploiting the reactivity of the P-atom of phosphole-based oligomers, we have achieved access to the first organophosphorus-containing organic light-emitting diode (OLED) materials. The versatility of these P-materials is demonstrated with the synthesis of a corresponding gold complex that has also been used as an OLED material. Optimization of the OLED devices by doping the phosphole layer with a red fluorescent dye is described.     

Definition and measurement of the normalized electrical impedance of lossy piezoelectric resonators for ultrasonic transducers

Relevant equivalent circuit parameters and values of material constants of a piezoelectric resonator can be determined from measurements of its electrical input impedance as a function of frequency. The complex electrical impedance curves and the associated critical frequencies are the basis of this characterization by the piezoelectric resonance method. In this paper, the previously introduced concept of normalized electrical impedance of the lossy resonator, extended to include piezoelectric losses, is applied to the analysis of the effects of different types of intrinsic losses on peak values, bandwidths and characteristic frequencies. The resulting impedance patterns depend solely on the electromechanical coupling coefficient and the loss tangents, providing a useful tool for the analysis of low-Q resonators. The normalized impedance is experimentally evaluated from the basic data provided by an HP 4194A impedance analyser by means of specifically developed ASP programs.     

Resonance Raman Scattering of Undoped Trans-Polyacetylene in the Region of the Absorption Edge

Resonance Ranan Scattering of undoped CH)_X was studied for excitation wavelength λ_L between 700 and 1064 nm. Scattering is entirely due to long conjugated chains, but with evidence of disorder. Positions and shapes of the Raman lines are studied as a function of λ_L. The action spectrum shows a maximm near 1.4 eV, with a width > 0.2 eV at 2 K and no other structure.     

Hydrogenic systems,frequency standards and fundamental constants

Hydrogenic (two-body) systems are the only atomic systems for which uncertainties in calculations of the energy levels approach the current state of the art in frequency measurement. This article discusses progress in the theory and measurement of transition frequencies in hydrogenic systems. These studies have relevance to the determination of fundamental constants and the testing of physical theories, especially quantum electrodynamics. A set of high accuracy calculable frequency standards could also be realized by using hydrogenic systems.     

Influence of polymorphism on charge transport properties in isomers of fluorenone-based liquid crystalline semiconductors

We measured the charge carrier mobilities for two isomers of fluorenone-based liquid crystalline organic semiconductors from their isotropic down to crystalline states through one or two mesophases. Improved charge transport properties of melt-processed crystalline films were obtained for the isomer exhibiting a highly ordered mesophase below its disordered smectic phase.     

New Semiconducting Poly(arylene sulfide)s: Synthesis,Characterization, and Optical Properties

New semiconducting soluble poly(arylene sulfide)s were synthesized by Wittig polycondensation. The arylene moieties consist of distyrylbiphenyl (P1) and distyrylbithiophene (P2) π-conjugated systems. The polymers are fully amorphous and show good thermal stability. The absorption and photoluminescence properties of the polymers were investigated. P1 film has an optical gap of 2.95 eV and exhibits green-blue fluorescence. P2 shows a longer effective conjugation length with a gap of 2.42 eV and emits in the orange region. The HOMO/LUMO energy levels were estimated by cyclic voltammetry measurements. Single-layer diodes were fabricated and show relatively low turn-on voltages.