1,720,977 research outputs found
Ensembles of Gold Nanowires for the Anodic Stripping Voltammetric Determination of Inorganic Arsenic
No full text3D-ensembles of gold nanowires electrodes (3D-NEEs) are produced by electroless gold deposition in track-etched polycarbonate (PC) membranes, followed by partial etching (plama or chemical) of the polymeric membrane. These electrodes are applied to the anodic stripping voltammetric determination
of inorganic As. The controlled etching of the PC template increased the gold surface area, widening the linear range of the analytical response with respect to ensembles of gold nanodisk electrodes (2D-NEEs). 3D-NEEs prepared using a chemical etching time of 10 s allows the anodic
stripping determination of As(III) with a detection limit of 0.08 g/L and a linear range extended up to 20 g/L. The speciation of inorganic As As(III) and (As(V)) in river water is possible by difference between As(III) and total inorganic As, determined after reduction of As(V) with cysteine. The proposed method is successfully validated by comparison with ICP-MS determination
Pyrolyzed Photoresist Carbon Electrodes for Trace Electroanalysis of Nickel(II)
Full text linkNovel pyrolyzed photoresist carbon electrodes for electroanalytical applications have been produced by photolithographic technology followed by pyrolysis of the photoresist. A study of the determination of Ni(II) dimethylglyoximate (Ni-DMG) through adsorptive cathodic stripping voltammetry at an in situ bismuth-modified pyrolyzed photoresist electrode (Bi-PPCE) is reported. The experimental conditions for the deposition of a bismuth film on the PPCE were optimized. The Bi-PPCE allowed the analysis of trace concentrations of Ni(II), even in the presence of Co(II), which is the main interference in this analysis, with cathodic stripping square wave voltammograms characterized by well-separated stripping peaks. The calculated limits of detection (LOD) were 20 ng∙L−1 for Ni(II) alone and 500 ng∙L−1 in the presence of Co(II). The optimized method was finally applied to the analysis of certified spring water (NIST1640a)
Optimization of carbon electrodes derived from epoxy-based photoresist
Full text linkIn this contribution we report on results from an optimization study of SU-8 photoresist derived carbon electrodes. SU-8 derived carbon tends to be glassy in nature, however, based on the exact pyrolysis strategy and other fabrication parameters employed one can obtain a range of electrical, electrochemical and thermal properties related to the variation of the graphitic content of the thus obtained carbon. Hence, in order to obtain electrodes that emulate or improve upon the performance of commercially available glassy carbon (GC) electrodes, the right choice of pyrolysis conditions, and fabrication parameters such as the polymer patterning method, the nature of the substrate, polymer precursor film thickness and dimensions of the electrodes are all important. Carbon electrodes made employing a variety of pyrolysis times and pyrolysis end temperatures, film thicknesses and substrates are investigated by cyclic voltammetry of a redox probe ([Fe(CN)(6)](4-)), resistance measurements and spectroscopic analysis (Raman and XRD). SU-8 derived carbon electrodes displayed a wide potential stability window even in acidic media comparable to that of commercially available GC electrodes. Finally, these electrodes were applied to the simultaneous detection of traces of Cd(II) and Pb(II) through anodic stripping voltammetry and detection limits as low as 0.7 and 0.8 mu gL(-1) were achieved
Electroanalytical Applications of Sensors Based on Pyrolized Photoresist Carbon Electrodes
No full textPyrolyzed photoresist carbon electrodes (PPCEs) fabricated by photolithographic micro-fabrication and pyrolysis of the epoxy-based photoresist named SU-8 are applied to electroanalysis. Bismuth-modified PPCEs (Bi-PPCEs) are used in the adsorptive cathodic stripping voltammetry (AdCSV) of Ni(II) and in the speciation of inorganic Cr, while PPEs are used in the cyclic voltammetric (CV) study of bilirubin (BR) in dimethyl sulfoxide
Highly luminescent metal-organic frameworks through quantum dot doping
No full textThe incorporation of highly luminescent core-shell quantum dots (QDs) within a metal-organic framework (MOF) is achieved through a one-pot method. Through appropriate surface functionalization, the QDs are solubilized within MOF-5 growth media. This permits the incorporation of the QDs within the evolving framework during the reaction. The resulting QD@MOF-5 composites are characterized using X-ray fluorescence, cross-sectional confocal microscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and small-angle X-ray scattering. The synergistic combination of luminescent QDs and the controlled porosity of MOF-5 in the QD@MOF-5 composites is harnessed within a prototype molecular sensor that can discriminate on the basis of molecular size.Dario Buso, Jacek Jasieniak, Matthew D. H. Lay, Piero Schiavuta, Paolo Scopece, Jamie Laird, Heinz Amenitsch, Anita J. Hill and Paolo Falcar
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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