1,721,002 research outputs found
Near room temperature light-activated ws2-decorated rgo as no2 gas sensor
No full textThe NO2 response in the range of 200 ppb to 1 ppm of a chemoresistive WS2-decorated rGO sensor has been investigated at operating temperatures of 25 °C and 50 °C in dry and humid air (40% RH) under dark and Purple Blue (PB) light conditions (λ = 430 nm). Few-layers WS2, exfoliated by ball milling and sonication technique, with average dimensions of 200 nm, have been mixed with rGO flakes (average dimension 700 nm) to yield WS2-decorated rGO, deposited on Si3N4 substrates, provided with platinum (30 μm gap distance) finger-type electrodes. TEM analysis showed the formation of homogeneous and well-dispersed WS2 flakes distributed over a thin, continuous and uniform underlying layer of interconnected rGO flakes. XPS and STEM revealed a partial oxidation of WS2 flakes leading to the formation of 18% amorphous WO3 over the WS2 flakes. PB-light irradiation and mild heating of the sensor at 50 °C substantially enhanced the baseline recovery yielding improved adsorption/desorption rates, with detection limit of 400 ppb NO2 and reproducible gas responses. Cross sensitivity tests with humid air interfering vapor highlighted a negligible influence of water vapor on the NO2 response. A charge carrier mechanism between WS2 and rGO is proposed and discussed to explain the overall NO2 and H2O response of the WS2-rGO hybrids
Optical and conductometric gas sensing properties of sol-gel TiO2 films doped with Au nanoparticles
No full textTiO2 sol-gel films have been doped with colloidal
gold nanoparticles (NPs) and used as a platform for
optical and conductometric gas sensors for CO and H2
detection.
Optical gas sensors of this type require an
operating temperature above 300 °C. Measurements
performed at 360 °C showed a reversible gas-induced
variation of absorption spectra for both CO and H2.
The variation in absorbance depends on testing
wavelength and film annealing temperature.
Conductometric gas sensors showed excellent
performances toward H2 detection with a dynamic
response close to ideal
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
The influece of water vapour on carbon monoxide sensitivity of α-Fe2O3 microporous ceramic sensors
No full textVariations 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
Comparison of single and binary oxide MoO3, TiO2 and WO3 sol-gel gas sensors
No full textA systematic comparison of sol-gel prepared titanium dioxide (TiO2), WO3, and MoO3 single metal oxide based gas sensors was conducted. Process variables such as solution concentration, deposition parameters, gelling time, annealing time and temperature, remained constant. Sensors based on binary compound MoO3-TiO2 and MoO3-WO3 were also investigated to determine if the performance is superior to their single oxide constituents. The sensors were systematically exposed to O-2, O-3, CO and NO2 gases and ethanol vapor at concentration levels of particular interest. MoO3 binary compound based sensors showed promising O-3, CO and NO2 gas response. Their use as a sensing film for gas is limited due to the materials low evaporating temperature, limiting its operating temperature below 350 degreesC. However, the binary oxide of MoO3-WO3 showed a high response to ethanol vapor and a highly selective response to NO2. (C) 2002 Elsevier Science B.V. All rights reserved
2D Amorphous/Crystalline a-In2O3/In2Se3 Nanosheet Heterostructures with Improved Capability for H2 and NO2 Sensing
Full text linkSpontaneous degradation of 2D transition-metal dichalcogenides/chalcogenides (TMDs/MCs) gas sensors in dry/ wet air represents one of the most significant drawback of these interfaces, hampering the reproducibility of the baseline resistance and sensor's signal stability (i.e., sensor's creep). Herein, we report a simple protection strategy stimulating the formation of a self -assembled oxide (a-MOx) over TMDs/MCs, which promotes effective passivation of the underlying surface and excellent gas sensing response. Liquid-phase-exfoliated few-layers 2D-In2Se3 have been annealed in air at 180 degrees C for 24 h to yield an a-In2O3/In2Se3 heterostructure comprising a self-assembled a-In2O3 amorphous skin (5-10 nm) over 2D-crystalline In2Se3 (5-30 nm). The isomorphic conversion of In2Se3 into a-In2O3 specifically enables the layered shape of the precursor 2D-In2Se3 to be preserved after annealing, therefore providing all the surface-to-volume advantages of 2D interfaces. The excellent baseline and sensor's signal reproducibility to H2 (5-100 ppm) and NO2 (400 ppb-1 ppm) after 1 year of delivery at 100 degrees C operating temperature demonstrated that the oxide skin effectively passivates the underlying 2D-In2Se3 from further oxidation. Significantly, the a-In2O3/In2Se3 heterostructure shows better H2 sensing response with respect to 2D TMDs/MCs sensors, with experimental detection limits as low as 5 ppm H2 and 400 ppb NO2, with associated RR (Ra/Rg) = 2.1 to 100 ppm H2 and RR (Rg/Ra) = 2.3 to 1 ppm NO2 in dry air. A charge carrier mechanism between the a-In2O3/In2Se3 heterostructure and H2, NO2, and H2O molecules is presented to discuss the humidity cross response to H2 and NO2. The passivation strategy here proposed can be extended to a large variety of TMDs/MCs, opening new perspectives for the effective exploitation of layered amorphous gas-sensing interfaces
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