1,721,112 research outputs found
Electrochemiluminescence devices based on Novel materials for Biosensors
No full textThe main objective of this thesis was to discover highly efficient, cost effective and environmental friendly electrode material for the detection of Ruthenium Tris Bypiridil (Ru(bpy)32+) using ElectroChemiLuminescence (ECL) technique. In this regard different novel materials, Carbon NanoTubes (CNT), Bismuth oxide (Bi2O3), Bismuth oxychloride (BiOCl), Bi2O3/CNT composite, BiOCl/CNT composite, Carbon Fiber (CF), Silicon Carbide (SiC) and Biomass material, have been utilized as a working electrode (WE) in the ECL analysis. Throughout the ECL experiments, gold (Au) were used as an auxiliary electrode and silver/silver chloride (Ag/AgCl) were used as a reference electrode. Concerning CNT working electrode, self-standing cylindrical-shaped Multi-Walled Carbon NanoTubes (MWCNT) were grown by means of chemical vapour deposition (CVD) system. The bundles were initially back contacted with copper wire and then encapsulated into epoxy resin to provide electrical insulation. During the measurements, it was observed that emission of light is periodic and it last for hundreds of voltammetric cycles. The efficiency was found out to be far better than commercially used Glassy Carbon (GC) working electrode, used as a benchmark. The only problem with CNT was the non-reproducibility which we don't have in case of GC. The analysis showed that, even they are not cost-effective and environmental friendly; they are highly efficient and can be considered as disposable electrode material for ECL based biosensor platforms. On the other hand, different bismuth based materials were investigated as a WE in ECL experiments. Initially, Bi2O3, BiOCl and their composite with CNT were used to make different kind of pellets and then the process of electrical connection and encapsulation was performed. The ECL analysis showed that it is possible to have light emission with all bismuth based working electrodes but with lower intensities. Bismuth is considered to be cheap and less toxic then glassy carbon but the efficiency of bismuth based electrodes were found out to be lesser than glassy carbon. CF is now reached to a maturity level and they represent a growing industry with multitude of applications. Due to large surface area and high electrical conductivity, CF is widely used as electrode material for various applications. In order to exploit these properties, CF was also used as WE for ECL analysis. During the analysis, it has been noticed that the light emission were almost constant with very low deviation. The light emission with CF electrode was found to be even better than the standard glassy carbon electrode (GCE) used as benchmark. Sensitivity, bio-compatibility and low cost are the main characteristics which make CF a potential candidate for the future biosensor platforms. The superior bio-electric properties of SiC make it an ideal candidate for bio-electrodes. The SiC is considered to be one of the most favourable bio-compatible materials due to its hydrophilicity and rich surface chemistry. In this work three different kinds of SiC material; (1) SiC with SiO2 shell (2) SiC without SiO2 shell (3) SiC thin film, were used as working electrodes. The light emission with all these electrodes was found to be quite strong and stable in time. Biomass, are considered to be one of the best resources for the production of cost-effective and environmental friendly products. These solid wastes have the peculiarity of producing low ash and high carbon contents through the process of pyrolyzation and activation. In this work we have used Bamboo and Pistachio Nut Shells (PNS), two biomass materials, as a precursor for making working electrodes. Bamboo sticks were initially pyrolyzed, using metal oxide chemical vapour deposition (MOCVD) system. This work was carried out in order to prove the possibility of using less expensive carbon based electrodes for ECL analysis. It has also been showed the possibility of making electrodes through biomass materials. Initially bamboo was pyrolyzed in an argon fluxed oven at 850°C. In order to attain a high amount of purity, the surface of the resulted pyrolysed bamboo sticks were cleaned with an acid attack. The purity was later confirmed by XPS and TGA analysis. The experimental analysis showed that the bamboo electrodes have outstanding electrochemical properties than standard GC electrodes, even if they are lacking good reproducibility. The tubular structure of bamboo was found to be a vital factor for such higher ECL emissions and stability. In order to use PNS as working electrode in ECL experiments, initially, it was carbonized at 500°C for 2 hours by using Chemical Vapour Deposition (CVD) apparatus. Consequently, the Carbonized Pistachio Nut Shells (CPNS) were activated with KOH at 900°C in Argon atmosphere. Field Emission Scanning Electron Microscopy (FESEM) analysis confirmed the grain size, structural porosity, activation with KOH and elemental composition. The experimental analysis showed that the ECL efficiency and stability with CNPS electrodes are comparable with GC electrodes but like bamboo they are also lacking good reproducibility. The very low cost of the raw material combined with such good results make them good candidates for future ECL based disposable biosensor platform
Comparison of unusual carbon-based working electrodes for electrochemiluminescence sensors
No full textIn this work, unconventional carbon-based materials were investigated for use in electrochemiluminescence (ECL) working electrodes. Precursors such as bamboo, pistachio shells, kevlar® fibers and camphor were differently treated and used as working electrodes in ECL experiments. After a proper process they were assembled as electrodes and tested in an electrochemical cell. Comparison among them and with a commercial glassy carbon electrode (GCE) shows a very good response for all of them thus demonstrating their potential use as disposable low-cost electrodes for early detection electrochemical analysis
Pyrolyzed bamboo electrode for electrogenerated chemiluminescence of Ru(bpy)32+
No full textA novel, ultra low cost and environmental friendly electrode material for electrogenerated chemi- luminescence (ECL) was developed by pyrolyzing bamboo sticks. Scope of the work is to prove the use of carbon-based electrodes, in our case one of the less expensive possible, for doing electrochemical analy- sis based on ECL technology. It is also proved the very interesting possibility of producing electrodes by pyrolyzation of organic materials. The pyrolyzation was accomplished in an argon fluxed oven at 850◦C. The resulting pyrolyzed bamboo sticks were tested as electrodes, after their surface were cleaned with an acid attack to achieve a high degree of purity, as confirmed by TGA and XPS analysis. The bamboo electrodes showed higher ECL efficiencies and stability than standard glassy carbon ones, even if they still suffer of poor reproducibility. Typical bamboo tubular structure was found to be a key factor for such a great signal enhancement in electrochemical experiment
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
- …
