1,720,956 research outputs found
Studio del clustering del monostrato di molecole organiche passivanti nanoparticelle d'oro
Full text linkThe development of nanosystems or so-called "molecular machines" is a great challenge for modern chemistry. This acute scientific effort stems from the multiplicity and significance of the potential application fields, which could range from analytes sensing and biomedicine, to the design of "artificial enzymes", rationally designed supramolecules which possess intrinsic catalytic activity. A top-down approach implies the complete understanding of the mechanisms that govern the processes of formation, assembly and rearrangement of these supramolecules, in order to control and steer them in the desired direction.
Metal nanoclusters stabilized by an organic monolayer (SAM, Self-Assembled Monolayers) stand out into the varied review of nanomaterials, because of their particular features, which address them as one of the main platforms on which to shape the concept of molecular machine. The SAM which stabilize the metallic nucleus is nothing more than a supramolecular structure formed by molecules displaying special functional groups, which self-assemble upon the metallic surface, potentially reaching an high spatial organization. The possibility to change at will the chemical structure of adsorbates implies a considerable flexibility in modulating the physicochemical properties of these nanomaterials: to date gold nanoparticles (AuNPs) stabilized by alkyl and functionalized thiols, such as nucleic acids, oligopeptides, polysaccharides have been synthesized. Moreover, mixed SAM AuNPs synthesis has been reported in literature: in this case the properties of different types of adsorbates could be mediated, or possess synergistic activity.
In this Ph.D. Thesis several research projects have been developed, each one relating to specific properties and applications of omoligand and mixed monolayer AuNPs. Several experimental evidences reported in literature suggest that in mixed monolayer AuNPs, adsorbates could undergo phase segregation processes: in the first part, mixed monolayer gold nanoparticles stabilized by photoresponsive groups containing derivatives (azobenzene and pyrene) have been synthesized and characterized, in order to correlate the optical properties of the samples with the topological arrangement of adsorbates into the monolayer.
In the second part, the exposition focus upon nanoparticle gold core packing and monolayer’s self-assembly mechanisms in Peng-Scrimin synthetic process, the one commonly used in our laboratory. This study has been considered useful in order to increase accuracy of mixed monolayers synthesis and to explain the occurrence of "sorting" phenomena (asymmetric distribution of adsorbates onto metallic nuclei into the sample). The properties of some functionalized monolayers have also been investigated through exchange experiments, initially monitored by means of fluorescence emission spectroscopy and then by 1H- NMR, in order to justify experimental evidences of phase segregation recently published by the research group in which I spent the Doctorate .
In the third part, supramolecular interaction between mixed monolayer AuNPs (stabilized by a pyrene derivative co-adsorbed with a phosphorylcholine one) and single-walled carbon nanotubes (SWNTs), pristine (non-functionalized) and PEG-ylated (conjugated with polyoxyethylene chains), has been investigated, and a protocol for their complexation to the obtaining of nanocomposites has been develope
Noncovalent Interaction between Single-Walled Carbon Nanotubes and Pyrene-Functionalized Gold Nanoparticles in Water-Soluble Nanohybrids
No full textThe combination of different nanostructures in a multifunctional nanostructured hybrid is expected to improve their functionalities and lead to synergistic effects. In these regards, carbon nanotubes and gold colloids are well-studied building blocks with unique optical and electronic properties, which could be combined in a variety of optoelectronic applications. In this framework, we herein present an innovative approach to the preparation of water-soluble nanohybrids by noncovalent interaction between single-walled carbon nanotubes (SWCNTs) and gold nanoparticles (AuNPs) cofunctionalized with pyrenyl and choline residues. To this aim, we developed a procedure based on consecutive centrifugation steps, which allows straightforward isolation of the conjugates in their water-soluble form. Each step of the process was monitored by TEM and by UV–vis–NIR absorption spectroscopy to characterize the obtained nanohybrids and to confirm that the interaction of the pyrene residues of the cofunctionalized AuNPs with the nanotube walls is the only one responsible for the formation of the water-soluble nanohybrids. Further investigations including Raman spectroscopy and photoluminescence mapping confirm that the interaction between the AuNPs and the SWCNTs is arguably noncovalent and thus assures that the emission in the NIR region by the nanotubes is preserved. Measurements of the quenching of the fluorescence of pyrene by carbon nanotubes provide the association constants for complex formation between the cofunctionalized AuNPs and SWCNTs. The results reported herein provide the basis to novel strategies for the preparation of water-soluble nanohybrids between AuNPs and SWCNTs based on noncovalent interactions
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Innovative approaches to sustained drug release: in situ cross-linking Hyaluronic acid based scaffolds and thermoreversible polymers
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