1,720,989 research outputs found
Synthesis of organic semiconductors functionalized with biological molecules
No full textOrganic polymeric and molecular semiconductors functionalized with biological molecules represent a very interesting class of materials for highly selective electrical and optical sensors. Molecular design and synthetic approaches to several bio-substituted conjugated oligomers and polymers are discussed, highlighting the impact of synthetic pathways on the properties of the materials
Synthetic Routes to Extended Polyconjugated Structures
No full textThis review covers our recent contribution on the synthesis of extended polyconjugated compounds, such as conjugated polymers and small molecules. The synthetic strategies developed in our research group are mainly based on palladium-catalyzed cross-coupling reactions involving a variety of organometallic intermediates as well as on direct arylation reactions via C–H functionalization. This report is organized according to the synthetic methods used (coupling of unsaturated organosilanes, Suzuki–Miyaura cross-coupling, Stille cross-coupling, direct arylation) and the typologies of the structures synthesized (polymers, small molecules)
Non-covalent bridging of bithiophenes through chalcogen bonding grips
Full text linkIn this work, chalcogen functionalized dithiophenes, equipped on both extremities with chalcogen-bonding recognition heterocycles, have been prepared following two synthetic pathways. The insertion of the chalcogenazolo[5,4-β]pyridine allows the control of the organization at the solid state. X-Ray diffraction analysis of the single crystals, showed that the Te-doped derivatives give the most persistant assemblies, with the molecules arranging at solid-state in wire-like polymeric structures through Te⋯N interactions. As expected, the introduction of the Se and Te atoms, dramatically decreases the emission properties, with the Te-bearing congeners being virtually non emissive
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
Reductive amination reaction for the functionalization of cellulose nanocrystals
Full text linkCellulose nanocrystals (CNCs) represent intriguing biopolymeric nanocrystalline materials, that are biocompatible, sustainable and renewable, can be chemically functionalized and are endowed with exceptional mechanical properties. Recently, studies have been performed to prepare CNCs with extraordinary photophysical properties, also by means of their functionalization with organic light-emitting fluorophores. In this paper, we used the reductive amination reaction to chemically bind 4-(1-pyrenyl)butanamine selectively to the reducing termini of sulfated or neutral CNCs (S_CNC and N_CNC) obtained from sulfuric acid or hydrochloric acid hydrolysis. The functionalization reaction is simple and straightforward, and it induces the appearance of the typical pyrene emission profile in the functionalized materials. After a characterization of the new materials performed by ATR-FTIR and fluorescence spectroscopies, we demonstrate luminescence quenching of the decorated N_CNC by copper (II) sulfate, hypothesizing for these new functionalized materials an application in water purification technologies
Identification of volatile components of landmines and physiological response of olfactory neurons to the perfume of mines. Phase 1: GC-MS headspace analysis of landmines volatile components
No full textSynthesis and Chiroptical Characterization of an Amino Acid Functionalized Dialkoxypoly(p-phenyleneethynylene)
No full text2,5-Dialkoxypoly(p-phenyleneethynylene) (3) functionalized with N-t-BOC-L-phenylalanine molecules was synthesized by Pd-catalyzed reaction of dioctyloxybis[(trimethylsilyl) ethynyl] benzene (1) with aromatic diiodide 2 linked to two amino acid units by six carbon atoms alkoxy chains. Optical properties were investigated both in solution and in the solid state (as thin films) by absorption, fluorescence and chiroptical spectroscopies (CD and CPL). Polymer 3, that represents one of few fully characterized dialkoxy-substituted PAEs, is also the first example of a poly(aryleneethynylene) (PAE) with amino acidic chiral pendants
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