1,720,969 research outputs found
Laccase and tyrosinase on electrochemically reduced GO and MWCNTs hybrid for the development of polyphenols biosensors
No full textCarbon nanomaterials as glassy carbon modifiers for electrochemical devices with boosted activity
Full text linkGlassy carbon electrodes (GCEs) modified with a composite made of multi-walled carbon nanotubes (MWCNTs)
and electrochemically reduced graphene oxide (ERGO) were employed to investigate the electroactivity of
dopamine (DA) an catechol (CA) which resulted into a significant improvement of the analytical performances.
The same composite was used to support tyrosinase or laccase in order to fabricate amperometric biosensors for
determining total polyphenols in juice samples, based on the reduction of the enzymatically produced quinone.
Carbon based nanomaterials were also exploited to induce the electrosynthesis of layered double hydroxides
(LDHs). Using glucose as target, electrocatalytic activity was found to be higher than when LDH was deposited on
bare GCE
Modified Electrodes for Energy and Sensing Applications
No full textThis thesis describes the research focused on the study of different electrode supports modified with layered double hydroxides (LDHs) on Co or Ni as M(II) and Al or Fe as M(III) or conducting polymers for energy applications. The LDHs were characterized by electrochemical techniques, FE-SEM, XRD, XPS and XAS. Glassy carbon and Pt electrodes modified with electrosynthesized LDHs were employed in order to investigate their performances as oxygen evolution reaction catalysts and as pseudocapacitor materials. Moreover, the electrochemical synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) on indium tin oxide (ITO) was carried out in order to exploit an alternative route to fabricate bulk heterojunction solar cells with similar performances but less expensive than those obtained by casting. The photoactive layer was composed by [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) as electron acceptor, while as donor polymer it was employed either the commonly employed rr-poly(3-hexylthiophene) or a polythiophene copolymer, functionalized with a porphyrin derivative in order to improve the absorption in the UV/Vis region.
In the second part of the thesis, the LDHs modified electrodes were employed for sensing, taking into account the electrocatalytic oxidation of sugars. Ni/Al or Ni/Fe LDHs were studied with the aim to investigate again the effect of Fe on the electrocatalysis. LDHs prepared both by chemical and electrochemical syntheses were employed with the aim of studying the effect of the order degree on the LDHs performance since this parameter is crucial to improve the “sensing” properties. Furthermore, a sensor for the amperometric detection of sugars in flow systems, based on Co/Al LDH electrosynthesized on Pt electrodes, was developed. A mixture of sugars was submitted to high performance anion chromatography with amperometric detection, using the modified electrode as the working electrode. Moreover, to assess the applicability of the device glucose, fructose, and sucrose content in real samples were successfully determined
Ni/Al Layered Double Hydroxide and Carbon Nanomaterial Composites for Glucose Sensing
Full text linkLayered
double hydroxides (LDHs) have been combined with graphene
and/or carbon nanotubes to prepare new composite materials with fascinating
electrochemical features. For the first time, this work describes
the development of an electrosynthesis protocol that allows the deposition
of thin films of a Ni/Al LDH on glassy carbon electrodes previously
modified with carbon nanomaterials. Three different approaches (potentiostatic,
galvanostatic, and potentiodynamic) were investigated to identify
the best procedure. In all cases the potentiodynamic synthesis exhibits
better reproducibility than the potentiostatic one which is the most
used in the literature. The reliability of the synthesis protocol
was evaluated by performing the LDH electrodeposition using glassy
carbon electrodes modified with multiwalled carbon nanotubes and/or
electrochemically reduced graphene oxide arranged in five configurations.
XRD and SEM analysis confirmed the LDH formation. Cyclic voltammetry
shows the graphene presence ensured a large electrochemically active
area with values 3 times higher than the one observed for an LDH deposited
on a bare glassy carbon. Moreover, impedance electrochemical spectroscopy
highlights that carbon nanomaterials play a key role in reducing the
charge transfer resistance. In fact, it decreases from 2800 KΩ
recorded for LDH deposited on bare glassy carbon to about 600 Ω
for the best composite material. The materials were tested for glucose
electrooxidation which was exploited for the fabrication of a sensor
with high sensitivity (2.6 A M–1 cm–2 for the best device) and low limit of detection (0.6 μM for
the best device)
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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