1,720,956 research outputs found
Hydrothermal Growth and Hydrogen Selective Sensing of Nickel Oxide Nanowires
No full textLow cost synthesis of nanostructured metal oxides for gas sensing application at low temperature is nowadays of crucial importance in many fields. Herein, NiO p-type semiconducting nanowires with polycrystalline structure were prepared by a facile and scalable hydrothermal method. Morphology and crystal structure of the NiO nanowires were investigated by scan electron microscopy, X-ray diffraction, and transmission electron microscopy. The nanostructured material was then tested as hydrogen sensor showing very good performance in terms of sensor response, stability, absence of drifts, and speed of response and recovery. The selectivity of the NiO sensor to hydrogen towards other gases (ethanol, ammonia, and liquefied petroleum gas) was found to be good
Comparative gas-sensing performance of 1D and 2D ZnO nanostructures
No full textIn this work we have grown one-dimensional (1D) and two-dimensional (2D) zinc oxide nanostructures. Changing the deposition parameters we were able to obtain ZnO nanowires with an average diameter of 80-250 nm. Nanosheets grown in different conditions show thickness values in the range 70-360 nm. These kinds of nanostructure have been used to fabricate conductometric gas sensors for liquid petroleum gas (LPG) detection. Different sensing parameters are investigated in both cases as a function of the dimensionality and size of the zinc oxide nanostructures. A first approximation of the "depletion layer sensing mechanism" is used to explain how the geometrical factors of one- and two-dimensional nanostructures affect their sensing parameters. The depletion layer affects two dimensions of nanowires and only one of nanosheets. This greatly improves the sensor response of 1D-nanostructures. On the other side two-dimensional nanostructures have a larger cross-section, which increases the base current, thus lowering the limit of detection. At the same operative conditions, nanowires show a better percentage response when compared to similar thickness nanosheets, but 2D nanosheets demonstrate an improved limit of detection (LoD). (C) 2015 Elsevier B.V. All rights reserved
A label-free electrochemical biosensor based on screen-printed electrodes modified with gold nanoparticles for quick detection of bacterial pathogens
Full text linkIn this study, carbon screen-printed electrodes (SPEs) modified with gold nanoparticles (AuNPs), were prepared for label-free detection of Escherichia coli(E. coli) O157. AuNPs were synthesized by an electrochemical method and then modified on the carbon SPEs to improve the stability and effectiveness of the biosensor. Anti-E. coli O157 antibody was immobilized on the modified SPEs via -NHS cross-linking. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were selected to investigate electrochemical properties of modified carbon SPEs in a 5.0 mM K3[Fe(CN)6]/ K4[Fe(CN)6] added with 0.1 M KCl as well as to detect E. coli O157 bacteria. Results showed that the carbon SPEs were successfully modified with AuNPs of 18.0 ± 1.6 nm. The electrochemical signal of modified SPEs was stable after CV cycles, and the charge transfer resistance (Rct) decreased approximately to half of its initial value. Importantly, electrochemical biosensors based on AuNPs-modified carbon SPEs could detect E. coli O157 in the range of 10–106 CFU/mL without labels. The limit of detection was found at 15 CFU/mL with a signal-to-noise ratio of 3:1, and the time of detection was about 30 min. The success of as-prepared biosensor could open a strategy of portable diagnostics for label-free and quick detection of bacterial pathogens causing food-borne diseases, hospital-acquired infections as well as the emerging and re-emerging infectious diseases
Eco-friendly facile synthesis of Co3O4-Pt nanorods for ethylene detection towards fruit quality monitoring
Full text linkEthylene, a biomarker widely employed for evaluating fruit ripening during storage, exists at extremely low concentrations. Therefore a gas sensor with high sensitivity and a sub-ppm detection limit is needed. In this work, porous Co3O4 nanorods were synthesized through a hydrothermal method involving Co(NO3)2, Na2C2O4, H2O and ethylene glycol (EG), followed by annealing at 400 degrees C in air. The surface of the porous Co3O4 nanorods was functionalized with Pt nanoparticles to enhance the ethylene sensing performance. The effect of Co3O4 surface functionalisation with Pt nanoparticles was investigated by adding different amounts of nanoparticles. The sensor's outstanding performance at the optimum working temperature of 250 degrees C is attributed to the synergy between the high catalytic activity of Pt nanoparticles and the extensive surface area of the porous Co3O4 nanorods. Compared to pure Co3O4, the 0.031 wt% Pt sensor showed better ethylene sensing performance with a response 3.4 times that of pristine Co3O4. The device also demonstrated high selectivity, repeatability, long-term stability and a detection limit of 0.13 ppm for ethylene, which is adequate for fruit quality monitoring. The gas sensing mechanism of porous Co3O4 nanorods and the influence of Pt decoration on sensor performance are discussed
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
- …
