69 research outputs found
Effect of molecular and electronic structure on the light harvesting properties of dye sensitizers
The systematic trends in structural and electronic properties of perylene
diimide (PDI) derived dye molecules have been investigated by DFT calculations
based on projector augmented wave (PAW) method including gradient corrected
exchange-correlation effects. TDDFT calculations have been performed to study
the visible absorbance activity of these complexes. The effect of different
ligands and halogen atoms attached to PDI were studied to characterize the
light harvesting properties. The atomic size and electronegativity of the
halogen were observed to alter the relaxed molecular geometries which in turn
influenced the electronic behavior of the dye molecules. Ground state molecular
structure of isolated dye molecules studied in this work depends on both the
halogen atom and the carboxylic acid groups. DFT calculations revealed that the
carboxylic acid ligands did not play an important role in changing the
HOMO-LUMO gap of the sensitizer. However, they serve as anchor between the PDI
and substrate titania surface of the solar cell or photocatalyst. A
commercially available dye-sensitizer, ruthenium bipyridine (RuBpy), was also
studied for electronic and structural properties in order to make a comparison
with PDI derivatives for light harvesting properties. Results of this work
suggest that fluorinated, chlorinated, brominated, and iyodinated PDI compounds
can be useful as sensitizers in solar cells and in artificial photosynthesis.Comment: Single pdf file, 14 pages with 7 figures and 4 table
Transport properties of copper phthalocyanine based organic electronic devices
Ambipolar charge carrier transport in Copper phthalocyanine (CuPc) is studied
experimentally in field-effect transistors and metal-insulator-semiconductor
diodes at various temperatures. The electronic structure and the transport
properties of CuPc attached to leads are calculated using density functional
theory and scattering theory at the non-equilibrium Green's function level. We
discuss, in particular, the electronic structure of CuPc molecules attached to
gold chains in different geometries to mimic the different experimental setups.
The combined experimental and theoretical analysis explains the dependence of
the mobilityand the transmission coefficient on the charge carrier type
(electrons or holes) and on the contact geometry. We demonstrate the
correspondence between our experimental results on thick films and our
theoretical studies of single molecule contacts. Preliminary results for
fluorinated CuPc are discussed.Comment: 18 pages, 16 figures; to be published in Eur. Phys. J. Special Topic
Molecular medicine and concepts of disease: the ethical value of a conceptual analysis of emerging biomedical technologies
Although it is now generally acknowledged that new biomedical technologies often produce new definitions and sometimes even new concepts of disease, this observation is rarely used in research that anticipates potential ethical issues in emerging technologies. This article argues that it is useful to start with an analysis of implied concepts of disease when anticipating ethical issues of biomedical technologies. It shows, moreover, that it is possible to do so at an early stage, i.e. when a technology is only just emerging. The specific case analysed here is that of ‘molecular medicine’. This group of emerging technologies combines a ‘cascade model’ of disease processes with a ‘personal pattern’ model of bodily functioning. Whereas the ethical implications of the first are partly familiar from earlier—albeit controversial—forms of preventive and predictive medicine, those of the second are quite novel and potentially far-reaching
Internet administration of three commonly used questionnaires in panic research : equivalence to paper administration in Australian and Swedish samples of people with panic disorder
This study assessed the degree of equivalence between paper and Internet administration of three measures of panic and agoraphobia-related cognition and behavior: Body Sensations Questionnaire (BSQ), Agoraphobic Cognitions Questionnaire (ACQ), and Mobility Inventory (MI). Participants were 110 people with panic disorder who had registered for an Internet-based treatment program in Sweden (n = 54) or Australia (n = 56). Participants were randomly assigned to complete the questionnaires via the differing administration formats in a counterbalanced order. Results showed broadly equivalent psychometric properties across administrations, with strong significant intraclass correlations between them, and comparable Cronbach\u27s alpha coefficients. A significant mean difference between administration formats was found for the BSQ only. In contrast to previous research, Internet administration did not generate higher scores than paper administration. No effect was found for order of administration. The findings suggest that each questionnaire can be validly administered via the Internet and used with confidence
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