1,720,980 research outputs found
Gamma Irradiation as a Tool for Modification of Graphene Oxide-Silver Nanowires Composites GAMMA IRRADIATION AS A TOOL FOR MODIFICATION OF GRAPHENE OXIDE-SILVER NANOWIRES COMPOSITES
Full text linkGraphene oxide (GO) was produced using the Hummers' method while silver nanowires (AgNWs) were obtained by polyol synthesis. Composite was produced by simple mixing of GO and AgNWs dispersions. The composite was produced in a form of free/standing films by vacuum filtration and exposed to gamma irradiation in an oxygen-free atmosphere. After irradiation, without any additional cleaning, the structure, morphology and electrical properties were investigated. Gamma irradiation was shown to be an efficient tool to induce a chemical reduction of GO, and it was able to improve the electrical conductivity of produced composites. Due to avoiding the usage of reagents and solvents, this method belongs to green chemical approaches
Application of graphene quantum dots in heavy metals and pesticides detection
Full text linkGraphene Quantum Dots (GQDs) were produced using electrochemical oxidation of graphite rods. Obtained GQDs were gamma-irradiated in the presence of the N atoms source, ethylenediamine. Both structural and morphological changes were investigated using UV-Vis, X-ray photoelectron and photoluminescence (PL) spectroscopy as well as atomic force microscopy. The ability of both types of dots to change PL intensity in the presence of pesticides such as malathion and glyphosate, as well as copper (II) ions was detected. These preliminary results indicated a high potential of produced GQDs to be applied as non-enzymatic PL sensors for the detection of selected pesticides and metal ions.26th International Symposium on Analytical and Environmental Problems, Szeged, Hungary, November 23-24, 202
Inkjet Printing Quasi-Miscible Droplets for Pseudo-Planar Organic Heterojunctions
No full textThe control of droplet mixing is of great interest for fundamental science (e.g. biomolecular
analysis, molecular diffusion, analytes separation) and emerging technologies in lab-on-chip devices (e.g. multiplexed biochips, micrototal analysis systems, Point-of-care) [1]. In this scenario, printing methodologies are a scalable and versatile approach for droplets production, resulting in
bespoke life-inspired platforms applicable to a vast range of disciplines [2], e.g. materials sciences, sensors, flexible electronics, and biotechnologies. Based on the rapid development of printing
techniques for the fabrication of photovoltaic devices [3], this work shows an innovative platform involving inkjet printing to fabricate pseudo-planar heterojunction (PHJ) organic solar cells (OSC)
on ITO/PET [4]. The process is based on the sequential deposition of two quasi-miscible inks
containing poly(3-hexylthiophene) (P3HT) and (6,6)-phenyl-C61-butyric acid methyl ester (PCBM), the model donor/acceptor couple for OSCs. The optimization of printing process consists in finding
a suitable ink formulation (chlorobenzene based for P3HT and chlorobenzene:dichlorometane in the
ratio 1:1 for PCBM), droplet velocity (about 7-8 m/s), droplet spacing ȝP, ultimately leading
to satellites-free spherical picolitre-scale droplets resulting in a continuous film on the ITO/PET
support. The chemical analysis of the PCBM-on-P3HT printed film is realized by atomic force
microscopy, X-ray photoelectron spectroscopy and fluorescence spectroscopy. The morphology is
characterized by a continuous and low roughness surface at the center of a printed droplet (average
roughness is about 1.3 nm), whereas nanometric aggregates at the droplet border are observed, as a
result of Marangoni flows mainly involving PCBM molecules. Such instabilities bringing molecular
recirculation to the droplet border agree with models developed for bisolvent droplets evaporation
[5]. XPS depth profile under mild sputtering (1 kV) permits to analyze the two printed layers,
demonstrating the lack of the separation of the P3HT and PCBM layers due the occurrence of
complete mixing. The almost complete quenching of the P3HT fluorescence emission band at about
655 nm due to the PCBM layer printed on top of P3HT confirms the effective formation of an
interface between the two films. The characterization of the solar cell device allows demonstrating
the goodness of the proposed approach, since the extracted parameters are quite similar (in
particular the power conversion efficiency) to those realized in a previous reference study which
employs spin coating deposition of the same materials in a glove box under inert nitrogen
atmosphere [6]. In conclusion, this study is a first step towards the analysis of functional interfaces
for the realization of a new class of inkjet printed PHJs and, in general, printed mixing interfaces
Pseudo-Planar Organic Heterojunctions by Sequential Printing of Quasi-Miscible Inks
Full text linkThis work deals with the interfacial mixing mechanism of picoliter (pL)-scale droplets produced by sequential inkjet printing of organic-based inks onto ITO/PET surfaces at a moderately high Weber number (~101). Differently from solution dispensing processes at a high Bond number such as spin coating, the deposition by inkjet printing is strictly controlled by droplet velocity, ink viscosity, and surface tension. In particular, this study considers the interfacial mixing of droplets containing the most investigated donor/acceptor couple for organic solar cells, i.e., poly(3-hexylthiophene) (P3HT) and (6,6)-phenyl-C61-butyric acid methyl ester (PCBM), showing how low-viscosity and low-surface energy inks can be leveraged for the fabrication of an interface suitable for a pseudo-planar heterojunction (pseudo-PHJ) organic solar cell (OSC) that is a convenient alternative to a bulk heterojunction (BHJ) OSC. The resulting thin-film morphology and molecular organization at the P3HT/PCBM interface are investigated, highlighting the roles of dissolution-driven molecular recirculation. This report represents a first step toward the sequential inkjet printing fabrication of pseudo-PHJ OSCs at low consumption of solvents/chemicals
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
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