1,720,993 research outputs found
NUOVI COMPOSTI OTTICAMENTE SENSIBILI AI COMPOSTI ELETTRONPOVERI
No full textsintesi di nuove molecole organiche per applicazioni sensoristich
NUOVI POLIMERI OTTICAMENTE SENSIBILI A COMPOSTI ELETTRONPOVERI
No full textnuovi materiali sintetizzati per applicazioni sensoristich
Dye-Sensitized Solar Hydrogen Production: The Emerging Role of Metal-Free Organic Sensitizers
No full textThe production of hydrogen from sunlight and water is finding an increasingly important role in the production of clean fuels from sustainable and abundant energy sources. In this process, commonly referred to as artificial photosynthesis, the role of the dye sensitizer is critical for optimizing the harvesting of visible light and triggering the reduction reaction at the catalytic active site. In recent decades organometallic sensitizers have mainly been studied, often requiring the use of scarce and, in some cases, toxic elements. This microreview describes the state of the art in the use of metal-free organic sensitizers, highlighting advantages over their organometallic counterparts. The main design and synthetic strategies, specific properties, and device performances are presented. Thanks to recent advances and lower manufacturing costs, organic sensitizers seem set to be of increasing importance for next-generation clean fuels
Aggregated structures in Langmuir-Blodgett films of pyridinium-dicyanomethanide dyes
No full text4-[5-(Dicyanomethanido)thien-2-yl]-N-(n-hexadecyl)pyridinium (C16H33-PDCNT), 1, and 1-[N-(n-hexadecyl-4-pyridinio)]-2-[5-(dicyanomethanido)thien-2-yl]ethene (C16H33-PDCNTE), 2, belong to a class of push−pull zwitterionic molecules that strongly absorb in the visible region. These compounds possess a negatively charged dicyanomethanide group as a donor and an N-alkylpyridinium cation as an acceptor. These molecules are highly solvatochromic and very active for second-order nonlinear optical effects. A very interesting feature of these compounds is their aggregational behavior: in fact, both molecules examined in this work show sharp UV−vis absorption bands in different types of films obtained with the Langmuir−Blodgett (LB) technique. The aim of this work is to study the structural characteristics of LB films of compounds 1 and 2: in particular, a study of the sharp absorption peaks, due to aggregated forms, is important because these bands are photobleachable and can have interesting applications in the field of optical data storage
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
Tailored Metal‐Porphyrin Based Molecular Electrocatalysts for Enhanced Artificial Nitrogen Fixation to Green Ammonia
Full text linkAbstract Electrochemical nitrogen reduction (E‐NRR) is one of the most promising approaches to generate green NH3. However, scarce ammonia yields and Faradaic efficiencies (FE) still limit their use on a large scale. Thus, efforts are focusing on different E‐NRR catalyst structures and formulations. Among present strategies, molecular electrocatalysts such as metal‐porphyrins emerge as an encouraging option due to their planar structures which favor the interaction involving the metal center, responsible for adsorption and activation of nitrogen. Nevertheless, the high hydrophobicity of porphyrins limits the aqueous electrolyte–catalyst interaction lowering yields. This work introduces a new class of metal‐porphyrin based catalysts, bearing hydrophilic tris(ethyleneglycol) monomethyl ether chains (metal = Cu(II) and CoII)). Experimental results show that the presence of hydrophilic chains significantly increases ammonia yields and FE, supporting the relevance of fruitful catalyst‐electrolyte interactions. This study also investigates the use of hydrophobic branched alkyl chains for comparison, resulting in similar performances with respect to the unsubstituted metal‐porphyrin, taken as a reference, further confirming that the appropriate design of electrocatalysts carrying peripheral hydrophilic substituents is able to improve device performances in the generation of green ammonia
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