1,720,972 research outputs found
Dependence of the photoactivity of CdS prepared in butanol-ethylenediamine mixture in function of different sacrificial electron donors
No full textThe nanospheres and nanofibers of CdS were prepared by simple chemical precipitation method using a mixture of water:butanol:ethylenediamine solvents. The effect of either water or butanol as solvents and the volume ratio of butanol:ethylenediamine on the morphology, crystallinity, electronic and surface properties of CdS were investigated. The obtained CdS nanospheres or nanofibers were analyzed by X-ray diffraction, field emission scanning electron microscopy and diffuse reflectance spectroscopy. An evolution from nanospheres to nanofibers depending on the relative fraction of solvent and chemical species was observed, which was driven by the formation of Cd-complexes and S-polymerized precursors. The chemical composition and surface properties of CdS nanostructures as function of the butanol:ethylenediamine solvent ratio used for the synthesis were analyzed by X-ray photoelectron and infrared spectroscopies. The correlations between the morphology, crystallinity, electronic and surface properties with the photocatalytic activity of CdS was investigated in the bluephoto-assisted reduction of 4-Nitrophenol using hydrazine as sacrificial electron donors (SED ' s). The impact the others SED's in the presence of citric acid on the increasing of photoactivity of CdS as function of created shallow energetic states was investigated by photoelectrochemical characterization
Photocatalytic discoloration of methyl orange dye by δ-Bi2O3 thin films
No full textCubic delta bismuth oxide (δ-Bi2O3) thin films were deposited on glass substrates using magnetron sputtering onto Corning glass slides with different roughness. The efficiency of the Bi2O3 films as a photocatalytic semiconductor for the discoloration of dyes was tested by using methyl orange (MO) solutions as the probe under UV, sunlight and white light. Moreover, the effect of the substrate roughness, as a parameter to enhance the active surface area, was also evaluated. The results indicated that similar discoloration percentages (98% in 180 min) were obtained for the three illumination ranges for surfaces with average roughness below 1.5 μm. The discoloration reaction rate was significantly higher when the UV light was used in comparison to visible and sunlight. In order to appreciate the significance of these results, the photodiscoloration efficiency of the optimized δ-Bi2O3 films was compared to TiO2 films deposited by magnetron sputtering and TiO2-P25 Degussa particles. The outcomes showed better color removal of the dye when using the rough Bi2O3 thin films in comparison to both TiO2 materials, suggesting that δ-Bi2O3 films are a rather promising photocatalytic material. Moreover, the photoinduced wettability change of the films was measured showing that δ-Bi2O3 films present a photoinduced hydrophilicity, similarly to TiO2
Good practices for reporting the photocatalytic evaluation of a visible-light active semiconductor: Bi2O3, a case study
No full textIn this paper, we discuss the importance of distinguishing the contributions of photolysis, adsorption, sensitization, degradation and mineralization processes to the photocatalytic activity of a visible-light active semiconductor: Bi2O3. Based on this case study, we propose a follow-up work plan to obtain the relevant information and achieve proper interpretation of reported data to adequately infer the photocatalytic activity of the Bi2O3 material. To do so, we compared the changes in the theoretical and experimental absorbance spectra of three different dyes during the photodegradation process: rhodamine-B (RhB), acid blue 113 (AB) and indigo carmine (IC). Photocatalytic degradation of these dyes using the same semiconductor material (Bi2O3) was performed using the standard spectrocolorimetric method while taking care to appropriately consider the competing processes mentioned above. Furthermore, the degree of mineralization achieved due to the photocatalytic degradation of the dyes was obtained using the total organic carbon (TOC) analysis. The commonly used evaluation of the results suggests that a certain degree of photodegradation and mineralization was achieved. However, careful analysis indicates that this was mainly due to a decrease in the relative concentration of the dye molecules in the solution because of their adsorption on the surface of the semiconductor and not to complete degradation
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
No full text“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
No full textWe 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
Chemical induced porosity on BiVO4 films produced by double magnetron sputtering to enhance the photo-electrochemical response
No full textDispelling the Myths Behind First-author Citation Counts
No full textWe 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
- …
