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Biomedical subjects

G Leising

Publications and source records attributed to G Leising.

17 recordsLinked to original sources
PubMed2002

Time-resolved charge carrier generation from higher lying excited states in conjugated polymers.

Sub-ps three-pulse transient differential transmission spectroscopy using two excitation pulses is used to directly investigate the generation of charge carriers in ladder-type poly(para)phenyl in bulk film. The role of higher excited singlet states of both even and odd symmetry is examined and the dynamics of the major processes involved is described quantitatively. The charge generation efficiency is found to depend strongly on the delay between the two excitation pulses. This is explained by the interplay between internal conversion, excitation energy migration, and on-site vibronic relaxation.

Journal Article↗
PubMed2001

Polyfluorenes with polyphenylene dendron side chains: toward non-aggregating, light-emitting polymers.

A polyfluorene 12 has been prepared in which bulky polyphenylene dendrimer substituents suppress formation of long wavelength emitting aggregates, thus giving a polymer with pure blue emission. Absorption- and emission spectra and molecular modeling confirm that the bulky dendrimer side chains do not cause extra torsion between the fluorene units. New polyfluorenes with 9,9-diaryl substituents have been prepared to determine the minimum size of substituent necessary for aggregation suppression. An LED using 12 has been demonstrated to produce blue emission with onset voltages below 4 V.

Journal Article↗
PubMed2000

Geometry-dependent electronic properties of highly fluorescent conjugated molecules

We present a combined experimental/theoretical study of the electronic properties of conjugated para-phenylene type molecules under high pressure up to 80 kbar. Pressure is used as a tool to vary the molecular geometry and intermolecular interaction. The influence of the latter two on singlet and triplet excitons as well as polarons is monitored via optical spectroscopy. We have performed band structure calculations for the planar poly(para-phenylene) and calculated the dielectric function. By varying the intermolecular distances and the length of the polymer repeat unit the observed pressure effects can be explained.

Journal Article↗
PubMed1996

Physical aspects of dexibuprofen and racemic ibuprofen.

This article presents a comparative study of ibuprofen materials in their solid state. Ibuprofen crystallizes into two different structures for the S(+) enantiomer (dexibuprofen) and racemic ibuprofen. The crystal structure of ibuprofen, its optical absorption and photoluminescence, and the thermodynamic results (melting point and heat of fusion) are discussed. From these physicochemical properties, the authors conclude that dexibuprofen, which is the most active species pharmaceutically, and racemic ibuprofen are inherently different solid-state materials.

Anti-Inflammatory Agents, Non-Steroidal↗