1,720,964 research outputs found
Protestation des apostolischen Nuntius in der Schweiz gegen das Dekret des katholischen Grossen Raths des Kantons St. Gallen vom 28. Okt. 1833, die Bisthumsangelegenheiten betreffend
No full text[Filippo de Angelis]Genaue Datierung: "Luzern, den 22. November 1833. Der apostolische Nuntius bei der schweizerischen Eidgenossenschaft, Ph., Erzbischof von Carthago.
Aggregation of organic dyes on TiO2 in dye-sensitized solar cells models: an ab initio investigation
No full textA density functional theory (DFT), time-dependent DFT, and ab initio second order Møller-Plesset perturbation theory study of the aggregation of the metal free indoline D102 and D149 dyes on extended TiO(2) models is reported. By selecting the relevant dimeric arrangements on the TiO(2) surface and evaluating, at the same time, the associated spectroscopic response, an almost quantitative description of the extremely different aggregation behavior of the two dyes is provided. Nicely reproducing the experimental evidence, the present results predict strong aggregation interactions and a sizable red-shift of the absorption band in the case of D102, while negligible effects for D149. Our results open the possibility of computationally screening the various aggregation patterns and predicting the corresponding optical response, thus paving the way to an effective molecular engineering of further enhanced sensitizers for solar cell applications
Spectroscopic properties of cyclometallated iridium complexes by TDDFT
No full textWe provide a unified view of our recent work on TDDFT calculations on the class of Iridium(III) cyclometallated complexes, of relevance for their extensive use in OLED and LEEC devices. Our results, obtained for vastly different systems, allow us to trace some general conclusions concerning the modeling of these transition metal complexes. The effect of relativistic effects on both geometrical structures and emission properties is analyzed considering scalar relativistic corrections and quadratic response theory. Absorption spectra for these compounds can be satisfactorily reproduced by TDDFT calculations neglecting spin-orbit coupling, because of the strong intensity of singlet-singlet transitions which hinders the weaker singlet-triplet transitions. We also underline the importance of being able to simulate the emission spectra line-shapes, thus allowing for a direct comparison of calculated and experimental quantities and to estimate the emission color perceived by the human eye. Approximate treatments of spin-orbit coupling based on excited state analysis are in some case useful to rationalize experimental trends, but more rigorous and quantitative approaches are required for future applications. Finally, we stress the absolute relevance of solvation effects in the description of the excited states of this class of systems, with very large differences in the excited state properties calculated in vacuo and as a function of different solvents. These differences have profound consequences for the comprehension of the photophysical properties of this important class of systems and should always be considered in their effective modeling. On overall, our results indicate that electronic structure-driven tuning of the excited state properties of Iridium(Ill) cyclometallated complexes is possible, thus opening the way to a theoretical and computational strategy for the design of new phosphorescent compounds with specific target characteristics. (C) 2009 Elsevier B.V. All rights reserved
Theoretical design of phosphorescence parameters for organic electro-luminescence devices based on iridium complexes
No full textTithe-dependent density functional theory with quadratic response methodology is used in order to calculate and compare spin-orbit coupling effects and the main mechanism of phosphorescence of the neutral Ir(ppy)(3) and cationic [Ir(bpy)(3)](3+) tris-iridium compounds, [Ir(ppy)(2)(bpy)](+) and [Ir(2-phenylpyridine)(2)(4,4'-tert-butyl-2,2'-bipyridine](+) complexes, including also the recently synthesised [Ir(2-phenylpyridine)(2)(4,4'-dimethylamino-2,2'-bipyridine](+) and [Ir(2,4-difluorophenylpyridine)(2)(4,4'-dimethylamino-2,2'-bipyridine](+) dyes, where ppy = 2-phenylpyridine and bpy = 2,2'-bipyridine ligands. Comparison with the symmetric, lighter and more studied [Ru(bpy)(3)](2+) and [Rh(bpy)(3)](3+) complexes is also resented. Variations in lifetimes for Ir(ppy)(3) and [Ir(bpy)(3)](3+) dyes as well as for the mixed cationic complexes are well reproduced by the quadratic response method. All the ortho-metalated iridium compounds exhibit strong phosphorescence, which is used in organic light-emitting diodes (OLEDs) to overcome the efficiency limit imposed by the formation of triplet excitons. The results from the first principle theoretical analysis of phosphorescence have helped to clarify the connections between the main features of electronic structure and the photo-physical properties of the studied heavy organometallic OLED materials.</p
Electron bipolarons at the DMASnBr3–water interface: Effect on the photocatalytic hydrogen production
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Modeling ZnS and ZnO Nanostructures: Structural, Electronic, and Optical Properties
Full text linkWe report the computational modeling of ZnS
and ZnO nanostructures by defining realistic nanoparticle models
∼1.5 nm sized for each material and investigating their structural,
electronic, and optical properties by means of DFT/TDDFT
calculations. To provide a direct comparison of calculated data to
experimentally characterized nanoparticles, 3D (ZnX)111 nanoclusters
of prismatic shape have been set up starting from the bulk
wurtzite (X = O, S), with two different saturation patterns of the
polar surfaces. The investigated models have been optimized by
means of CarParrinello molecular dynamics and local geometry
optimization techniques. The investigated systems exhibit a
well-opened HOMOLUMO energy gap, without any artificial
intraband-gap states. TDDFT calculation of the lowest excitation
energies are in excellent agreement, within 0.1-0.2 eV, with the experimental absorption onsets reported for similarly sized ZnO
and ZnS nanoparticles (3.70 and 4.40 eV, respectively). We have also investigated the electronic structure of the considered
nanoparticles, with reference to the valence band structure, finding calculated binding energies for the Zn d-shell to be only slightly
displaced toward lower values compared to experimental values, possibly due to quantum confinement effects. This work provides
the required computational framework for modeling ZnX and in general II-VI semiconductor nanomaterials, opening the way to
simulation of ligand/semiconductor interactions
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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