1,720,993 research outputs found
Molecular and Supramolecular Architectures of Organic Semiconductors for Field Effect Transistor Devices and Sensors: a Synthetic Chemical Perspective
No full textOrganic field-effect transistors (OFETs) are key devices in organic electronics, and their performances largely depend on molecular structure and solid-state organization of the π-conjugated compounds used as semiconductors. This microreview reports several examples of materials for OFET devices and sensors, which have been selected to highlight the basic criteria of molecular design together with the synthetic logic driving the development of organic semiconductors. Versatile synthetic methodologies enable to optimize properties by tailoring molecular structures and functionalization, thus playing a key role in the progress of OFET technology, and more in general of organic electronics, which is emphasized in the discussion
Covalent Lysozyme Immobilization on Enzymatic Cellulose Nanocrystals
Full text linkNanostructured materials represent promising substrates for biocatalyst immobilization and activation. Cellulose nanocrystals (CNCs), accessible from waste and/or renewable sources, are sustainable and biodegradable, show high specific surface area for anchoring a high number of enzymatic units, and high thermal and mechanical stability. In this work, we present a holistic enzyme-based approach to functional antibacterial materials by bioconjugation between the lysozyme from chicken egg white and enzymatic cellulose nanocrystals. The neutral CNCs were prepared by endoglucanase hydrolysis from Avicel. We explore the covalent immobilization of lysozyme on enzymatic CNCs and on their TEMPO oxidized derivatives (TO-CNCs), comparing immobilization yields, material properties, and enzymatic activities. The materials were characterized by X-ray diffractometry (XRD), attenuated total reflectance Fourier Transform infrared spectroscopy (ATR-FTIR), bicinchoninic acid (BCA) assay, field-emission scanning electron microscopy (FE-SEM) and dynamic light scattering (DLS). We demonstrate the higher overall efficiency of the immobilization process carried out on TO-CNCs, based on the success of covalent bonding and on the stability of the isolated bioconjugates.TEMPO-oxidized cellulose nanocrystals (TO-CNCs) are an excellent substrate for the covalent immobilization of lysozyme from chicken egg white. The bioconjugates are synthesized, isolated and characterized and are potential candidates as antibacterial materials. imag
Synthesis of electroluminescent conjugated polymers for OLEDs
No full textThis chapter discusses the most important synthetic routes to the main classes of electroluminescent -conjugated polymers, highlighting advantages and limitations of the different methods in terms of versatility, stereo- and regioselectivity, efficiency. The discussion covers not only the synthesis of basic classes of polymers such as polyarylenes, poly(arylenevinylene)s, poly(aryleneethynylene)s, but describes routes to systems with more complex structures, including multifunctional copolymers and coordination polymers
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
High Yield Synthesis of Cellulose Nanocrystals From Avicel by Mechano-Enzymatic Approach
No full textCellulose nanocrystals are an important class of bio-based crystalline nanostructures, finding application in several technological fields, including paper and textile coating, biocomposite engineering, biocatalysts immobilization, etc. This study explores enzymatic hydrolysis of Avicel, using endoglucanase from Aspergillus niger, to find an environmentally friendly method to extract cellulose nanocrystals from cellulose sources. Enzymatic hydrolysis has the advantage of reduced energy consumption and higher environmental friendliness compared to acid hydrolysis. In this work, we report for the first time very high nanocrystals yield by combining mechanical pretreatment of the cellulose starting material with a ball miller and endoglucanase hydrolysis, as a result of an extensive optimization of reaction conditions. In particular, a ball milling pretreatment carried out for 50 minutes at 3 Hz, allowed to isolate enzymatic CNCs with 76 % yield and with crystallinity as high as 75 %. The materials were characterized by X-Ray diffractometry, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, dynamic light scattering, zeta potential and field emission scanning electron microscopy (FE-SEM). Their characteristics were compared with the properties of sulfated CNCs, prepared from Avicel by sulfuric acid hydrolysis. Our results are technologically relevant, as they contribute to the accessibility and sustainability of CNCs for a wide range of applications in various industries
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
Iron-catalyzed cross-coupling reaction of aryl Grignard reagents with bis(2-bromovinyl)benzenes
No full textFe(acac)(3) has been used as the catalyst in cross-coupling reactions of aryl Grignard reagents with 1,4-bis(2-bromovinyl)benzenes affording bis(2-arylvinyl) benzenes. Effects of alkoxy substituents on both reactants and of the temperature on the reaction outcome are investigated
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