1,720,962 research outputs found
A highly sensitive and selective biosensor based on nitrogen-doped graphene for non-enzymatic detection of uric acid and dopamine at biological pH value
No full textFew layered graphene nanosheets were successfully doped with nitrogen through microwave irradiation and thoroughly characterized by using electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The electrochemical efficiency of N-doped graphene toward enzyme-free detection of uric acid (UA) and dopamine (DA) at neutral pH (7.4) was studied by chronoamperometry and cyclic voltammetry measurements. At working potential of +0.3 V (vs. Ag/AgCl), N-doped graphene electrode revealed ultra-high sensitivity of 2.06 mA mM−1 cm−2 and low limit of detection (LOD) of 0.13 μM within a concentration range of 0 to 0.6 mM for UA detection. Also, at very higher potential of +1.8 V (vs. Ag/AgCl), N-doped graphene sensor exhibited a highly selective response toward DA with very low LOD of 4.5 nM and high sensitivity of 7.63 mA mM−1 cm−2 in a broad linear concentration range from 0.1 to 100 μM. Furthermore, the performance of UA and DA sensors in the real blood sample was satisfactory. © 20181
Microwave-assisted synthesis of graphene modified CuO nanoparticles for voltammetric enzyme-free sensing of glucose at biological pH values
No full textThe effect of graphene nanosheets on the glucose sensing performance of CuO powders was investigated. CuO and graphene-modified CuO nanoparticles (NPs) were fabricated by microwave-assisted synthesis and characterized by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The material was placed on a glassy carbon electrode (GCE) which then was characterized by cyclic voltammetry and chronoamperometry with respect to the capability of sensing glucose both at pH 13 and pH 7.4. The results revealed that the modified GCE has a fast and selective linear response to glucose at pH 13 that covers the 0.21 μM to 12 mM concentration range, with a 0.21 μM low detection limit. The presence of graphene nanosheets results in an improved sensitivity which is to 700 μA mM−1 cm−2. In solution of pH 7.4, the respective data are a linear analytical range from 5 to 14 mM; a 5 μM LOD and a sensitivity of 37.63 μA mM−1 cm−2 at working potential of −0.05 V (vs. Ag/AgCl) and scan rate of 50 mV s−1. Ascorbic acid, dopamine, uric acid, sucrose, maltose and fructose do not interfere. [Figure not available: see fulltext.]. © 2017, Springer-Verlag GmbH Austria, part of Springer Nature.1
Synthesis and electrocatalytic performance of high loading active PtRu multiwalled carbon nanotube catalyst for methanol oxidation
No full textMultiwalled carbon nanotube (MWCNT) supported PtRu catalyst was prepared by improved aqueous impregnation method. The catalyst nanoparticles were characterized by using high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. According to the results of physicochemical characterization, PtRu alloy nanoparticles with low content of surface oxidation states were successfully synthesized on the outer surface of MWCNT supporting materials. Electrocatalytic activity of catalyst materials was investigated by using electrochemical half cell and CO stripping analyses. Results of electrochemical measurements indicate that the prepared PtRu/MWCNT catalyst shows an enhanced electrochemical activity toward methanol oxidation and a high electrocatalytic activity for CO oxidation. It is believed that superior performance of the PtRu/MWCNT catalyst is mostly attributed to the high degree of alloy formation and low contents of oxidized species of Pt and Ru. © 2012 Elsevier Ltd. All rights reserved.
Tungsten carbide on directly grown multiwalled carbon nanotube as a co-catalyst for methanol oxidation
No full textMultiwalled carbon nanotubes (MWCNT) were grown directly on the surface of graphite rod by using CVD process and then modified with tungsten carbide by carbothermal hydrogen carbonization technique. Then, platinum nanoparticles were deposited on the MWCNTs by means of electrodeposition technique. Catalyst materials were characterized by electron microscopy, X-ray photoelectron spectroscopy and three electrode electrochemical measurements. Catalysts supported on the directly grown MWCNTs exhibit notably better electrocatalytic performance towards methanol oxidation compared to the commercial Pt/C catalyst. Modification of MWCNTs with tungsten carbide was shown to further increase the catalyst performance. It is believed that the superior performance of catalysts prepared on the MWCNTs as catalyst support results mostly from the superior electrical contact and unique spatial configuration of the directly grown MWCNTs, while the positive effect of the tungsten carbide co-catalyst is mostly attributed to its improved resistance towards poisoning with the reaction intermediates produced during the methanol oxidation. © 2012 Elsevier B.V.
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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Get PDFWe 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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