1,721,042 research outputs found
Investigation of the nonlinear absorption of [M(Et2timdt)2] (M = Pd, Pt) in the pico- and nanosecond timescales using the Z-scan technique
No full textThe nonlinear optical absorption of two neutral metal dithiolenes [M(Et2timdt)2] (M=Pd and Pt) has been investigated at λ = 1064 nm by the open-aperture Z-scan technique using nanosecond and picosecond pulses. For picosecond photoexcitation, both dithiolenes mainly exhibit saturable absorption. Conversely, using nanosecond pulses, a switch from saturable absorption to reverse saturable absorption has been observed depending on the central metal. Based on experimental results, energy-level structures are suggested to explain the nonlinear absorption for both temporal regimes and, in particular, the sign-reversal of nonlinear absorption
Wavelength-Selective Organic Photodetectors for Near-Infrared Applications Based on Novel Neutral Dithiolenes
No full textBased on a new general class [M(R,R'timdt)2] of neutral dithiolenes, an innovative photodetector has been developed. By casting the organic material onto an opportunely configured quartz substrate a planar metal-semiconductor-metal structure has been obtained. Thanks to the strikingly intense absorption in the near infrared of these compounds, the device photoconductivity is enhanced when the irradiating wavelength belongs to this region of the spectrum. The device therefore acts as an intrinsically wavelenth-selective photodetector
Metal-Dithiolenes of Disubstituted Imidazolidine-2,4,5-trithione Monoanion. An Electrochemical and EPR Study
No full textThe electrochemical properties of a series of [M(R,R’timdt)2] dithiolenes (M = Ni, Pd, Pt; R,R’timdt = monoanion of disubstituted imidazolidine-2,4,5-trithione) have been studied by cyclic voltammetry, controlled potential coulometry, and EPR spectroscopy. All the compounds undergo two separate one-electron reductions and one two-electron oxidation, which proceed through a single step in the case of nickel complexes, and through two separate steps in the case of palladium and platinum complexes. Inductive effects played by the R and R’ substituents influence the formal electrode potentials of the electron transfer processes. EPR spectroscopy has proved that the unpaired electron in monoanions [M(R,R’timdt)2]− is located on a SOMO, which, even if mainly ligand centred, is significantly contributed by the metal
Synthesis, linear and nonlinear optical properties of [M(R,R'timdt)2] metal-dithiolenes for NIR applications (M = Ni, Pd, Pt; R,R'timdt = disubstituted monoreduced imidazolidine-2,4,5-trithione)
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Near-Infrared Detection By Means of Coordination Complexes
No full textWe report on the detection of near infrared (NIR) radiation in the range 900-1600 nm by means of coordination complexes such as [M(R,R’timdt)2]x– (M = Ni, Pd, Pt; R,R’timdt = formally monoreduced disubstituted imidazolidine-2,4,5-trithione; x = 0, 1), and [{Ru(bipy)2}2(μ-L)]x+ (H3L = 9-phenyl-2,3,7-trihydroxy-6-fluorone; x = 1, 3). By exploiting these stable coordination complexes absorbing in the visible and NIR region, the poor stability to air and light usually found in low band-gap organic semiconductors can be overcome. [M(R,R’timdt)2] and [{Ru(bipy)2}2(μ-L)]1+ complexes show π-π* transitions in the range 700-1000 nm, which can be bathochromically shifted by changing their oxidation state. Taking profit of this feature, we prepared photodetecting devices operating in the NIR region up to 1600 nm, thus reaching the appealing spectral range of telecommunications. NIR quantum efficiencies of these preliminary photodetectors, made by simple casting from solution, are comparable to those in the visible of most devices based on pristine organic materials. We succeeded in detecting train pulses with a repetition frequency of about 200 kHz at 960 nm and 80 kHz at 1450 nm, to our knowledge an unprecedented result that demonstrates the possibility to enter the NIR region by organic molecular-based devices
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
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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