1,720,961 research outputs found
Controlled Functionalization of Graphene Layers
No full textControlled functionalization of graphene layers is one of the most important research objectives in the material chemistry. A well established procedure is the oxidation with strong acids and oxidizing agents often in harsh and dangerous reaction conditions giving products of unknown precise structure. In this chapter, the controlled functionalization of graphene layers with a derivative of serinol is presented, avoiding toxic reagents and dangerous reaction conditions. The derivative is the bio‐based serinol pyrrole, obtained through the neat reaction of serinol with 2,5‐hexanedione; the graphitic substrate was high surface area graphite (HSAG) with high‐shape anisotropy. The functionalization reaction, characterized by a 85% atomic efficiency (water is the only by‐product), evolved with high yields leading to functionalized graphene layers through the controlled introduction of oxygen and nitrogen‐containing functional groups. Sustainable processes were adopted, such as ball milling and heating. The mechanism pathway, the characterization of HSAG and reaction products through a wide range of analytical methods, some successful applications of the adducts are discussed in this chapter. The functionalization left the bulk crystalline structure of the layers substantially unaltered. Stable dispersions in water and eco‐friendly solvents were prepared
C-H and C-C bonds activation by iridium clusters: Synthesis and solid state structure of [Ir6(CO)14(μ3- η1:η2:η1-C7H 8)]
No full textThe reaction between norbornene (C7H10) and Ir 6(CO)16 in refluxing toluene yields the substituted cluster [Ir6(CO)14(C7H8)]. In the solid state, the six iridium atoms define an octahedral metal cage, and one face is capped by the C7H8 ligand, coordinated through a 1,2-vinylidene unit. The loss of two hydrogen atoms from the olefin is, presumably, the result of a double oxidative addition of its C-H bonds, followed by elimination of a hydrogen molecule from the cluster. The bonding parameters of the organic fragment, as well as the architecture of the carbonyl ligands, closely match those found in the alkyne-substituted [Ir6(CO) 14(PhCCPh)] complex. The cluster [Ir6(CO) 14(C7H8)] was characterized through 1H-, 13C- and bidimensional COSY NMR. © 2005 Elsevier B.V. All rights reserved
Annealing effect on electromechanical behaviour of polyanilines organic acids-doped
No full textThis work presents an extensive experimental qualification of an innovative polyaniline synthesized by a more sustainable approach as sensing element. The electromechanical properties of polyanilines prepared by two different approaches (PANI1 from a traditional method and PANI2 from a more environmentally friendly route) are investigated in order to verify the applicability of these materials for the development of force and pressure transducers. The two PANI were chemically characterised and investigated through several mechanical tests. The variation of their resistance was continuously monitored during loading/unloading cycles up to 40 kN after heat treatment in order to evaluate the modification of the electromechanical properties at different temperatures. It was observed that both the polyanilines exhibit a strong change of their resistance value as function of the compression load acting on the samples. Moreover, PANI2 shows a high resistance which is a good property for insert the element into any measurement circuit avoiding problems of impedance losses due to cables or other circuit elements. The results will also show that both PANIs have steady behaviour at high temperatures up to 85°–100 °C
Electromechanical properties of polyanilines prepared by two different approaches and their applicability in force measurements
No full textThe present work highlights the possibility to employ an innovative green polyaniline as sensing device for force or pressure measuring systems. The electromechanical properties of polyanilines prepared by two different approaches (PANI1 from a traditional method and PANI2 from a green route) were investigated and their variation of resistance during loading/unloading cycles (0-100 kN) were compared. We observed that PANI2 shows similar piezoresistivity to PANI1 but higher electromechanical response and higher resistance that makes it more suitable for this kind of applications
On the cytotoxicity of poly(4-aminodiphenylaniline) powders: Effect of acid dopant type and sample posttreatment
No full textThanks to their unique properties, as intrinsic conductivity and simple preparation, conducting polymers are highly applicable in tissue engineering, regenerative medicine, and biosensors. Pristine polymers often include residual precursors or other low molecular impurities, which have a negative impact on their biocompatibility. Concerning poly(4-aminodiphenylaniline), its cytotoxicity and biocompatibility have not yet been investigated. Herein, the cytotoxicity of poly(4-aminodiphenylaniline), prepared by an innovative green approach, as well as the effect of samples' posttreatment and kind of dopant acid used, are reported for the first time. The results show that not only the type of used dopant but also polymers' washing in phosphate saline buffer and material's morphology has a significant impact on materials' cytotoxicity. After a proper posttreatment or when salicylic acid is used as the doping agent the cytotoxicity of poly(4-aminodiphenylaniline) seem to be lower than those obtained for traditional PANI.Ministry of Education, Youth and Sports of the Czech Republic-Program NPU I [LO1504]; Fondazione Cariplo (Milano, Italy) [2012-0872
Advances in poly(4-aminodiphenylaniline) nanofibers preparation by electrospinning technique
No full textPolyaniline (PANI) nanofibers are drawing a great deal of interest from academia and industry due to their multiple applications, especially in biomedical field. PANI nanofibers were successfully electrospun for the first time by MacDiarmid and co-workers at the beginning of the millennium and since then many efforts have been addressed to improve their quality. However, traditional PANI prepared from aniline monomer shows some drawbacks, such as presence of toxic (i.e., benzidine) and inorganic (salts and metals) co-products, that complicate polymer post-treatment, and low solubilityin common organic solvents, making hard its processing by electrospinning technique. Some industrial sectors, such as medical and biomedical, need to employ materials free from toxic and polluting species. In this regard, the oxidative polymerization of N-(4-aminophenyl)aniline, aniline dimer, to produce poly(4-aminodiphenylaniline), P4ADA, a kind of PANI, represents an innovative alternative to the traditional synthesis because the obtained polymer results free from carcinogenic and/or polluting co-products, and, moreover, more soluble than traditional PANI. This latter feature can be exploited to obtain P4ADA nanofibers by electrospinning technique. In this paper we report the advances obtained in the P4ADA nanofibers electrospinnig. A comparison among polyethylene oxide (PEO), polymethyl methacrylate (PMMA) and polystyrene (PS), as the second polymer to facilitate the electrospinning process, is shown. In order to increase the conductivity of P4ADA nanofibers, two strategies were adopted and compared: selective insulating binder removal from electrospun nanofibers by a rinsing tratment, afterwards optimizing the minimum amount of binder necessary for the electrospinning process. Moreover, the effect of PEO/P4ADA weight ratio on the fibers morphology and conductivity was highlighted
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
- …
