1,721,274 research outputs found
3D-(p/p/n) NiO/NiWO4/WO3 heterostructures for the selective detection of ozone
No full textWe propose 3D branched-like NiO/NiWO4/WO3 nano-heterostructures for the selective detection of ozone (O-3) at ppb levels, which is crucial for environmental and public health protection. These complex nano-heterostructures were fabricated using a combination of the vapor-liquid-solid and vapor-solid mechanisms, during which the reaction between NiO and WO3 leads to the formation of an intermediate seed, i.e., NiWO4. By controlling the charge transport within the nano-heterostructure through modulation of the operating temperature, sensors demonstrated highly selective sensing performances toward O-3 compared to NiO and WO3 nanowire sensors. At 300 degrees C, a response as high as 4709 +/- 9 was observed for 300 ppb of O-3 gas. In fact, we were able to achieve high selectivity toward O-3 compared to other highly reactive oxidizing compounds such as NO2. Due to their remarkable sensing performance, these heterostructures are leading candidates for the fabrication of future-generation miniaturized sensing devices for environmental and/or health monitoring
Shelf Life Study of NiO Nanowire Sensors for NO2 Detection
No full textAbstract: In this letter, conductometric sensing devices based on VLS grown NiO nanowires were presented for the detection of low concentrations of NO2. Moreover, the shelf life of sensing devices stored in ambient environmental conditions was tested over a period of 6 months. The VLS grown NiO nanowires were uniform in nature, covering completely the substrate surface area, with diameters ranging from 10 to 50 nm. The sensing devices show excellent performances, such as good stability, high response, outstanding selectivity toward NO2 and low detection limit. The devices were tested toward different analytes such as H2, acetone, NO2, etc. Indeed, at optimal working temperature, they show highly selective behavior towards NO2. Finally, the shelf life study reports that, due the exposure to the atmosphere, NiO nanowires exhibit a decrease in their conductivity, which enhances the response of the sensor. Graphic Abstract: [Figure not available: see fulltext.
ZnO Nanowires/Self-Assembled Monolayer Mediated Selective Detection of Hydrogen
No full textWe are proposing a novel self-assembled monolayer (SAM) functionalized ZnO nanowires (NWs)-based conductometric sensor for the selective detection of hydrogen (H2). The modulation of the surface electron density of ZnO NWs due to the presence of negatively charged terminal amine groups (-NH2) of monolayers leads to an enhanced electron donation from H2 to ZnO NWs. This, in turn, increases the relative change in the conductance (response) of functionalized ZnO NWs as compared to bare ones. In contrast, the sensing mechanism of bare ZnO NWs is determined by the chemisorbed oxygen ions. The functionalized ZnO NWs exhibit an eight times higher response compared to bare ZnO NWs at an optimal working temperature of 200 degrees C. Finally, in comparison to studies in the literature involving strategies to enhance the sensing performance of metal oxides toward H2, like decoration with metal nanoparticles, heterostructures, and functionalization with a metal-organic framework, etc., SAM functionalization showed superior sensing results
Materials Engineering for Chemical Sensing Enhancement
No full textMetal oxides nanowires and novel heterostructures are synthesized using different techniques and finally integrated into gas sensing platform. In particular, nanowires were synthesized using thermal oxidation and VLS mechanism. While, heterostructures i.e. NiO/ZnO (p-n) and NiO/NiWO4/WO3 (p-p-n) were synthesized using VLS and VS mechanisms. Detailed investigations reveal the dependence of sensors selectivity and sensitivity on nanowires synthesis techniques. While, the superior performance of heterostructures as compared to bare nanowires presents the novel pathway to further enhance the performance of nanostructured gas sensors
One-Dimensional Nanostructured Oxide Chemoresistive Sensors
No full textDay by day, the demand for portable, low cost, and efficient chemical/gas-sensing devices is increasing due to worldwide industrial growth for various purposes such as environmental monitoring and health care. To fulfill this demand, nanostructured metal oxides can be used as active materials for chemical/gas sensors due to their high crystallinity, remarkable physical/chemical properties, ease of synthesis, and low cost. In particular, (1D) one-dimensional metal oxides nanostructures, such as nanowires, exhibit a fast response, selectivity, and stability due to their high surface-to-volume ratio, well-defined crystal orientations, controlled unidirectional electrical properties, and self-heating phenomenon. Moreover, with the availability of large-scale production methods for nanowire growth such as thermal oxidation and evaporation-condensation growth, the development of highly efficient, low cost, portable, and stable chemical sensing devices is possible. In the last two decades, tremendous advances have been achieved in 1D nanostructured gas sensors ever since the pioneering work by Comini on the development of a SnO2 nanobelt for gas sensor applications in 2002, which is one such example from which many researchers began to explore the field of 1D-nanostructure-based chemical/gas sensors. The Sensor Laboratory (University of Brescia) has made major contributions to the field of metal oxide nanowire chemical/gas-sensing devices. Over the years, different metal oxides such as SnO2, ZnO, WO3, NiO, CuO, and their heterostructures have been grown for their nanowire morphology and successfully integrated into chemoresistive gas-sensing devices. Hence in this invited feature article, Sensor Laboratory research on the synthesis of metal oxide nanowires and novel heterostructures and their characterization and gas-sensing performance during exposure to different gas analytes has been presented. Moreover, some new strategies such as branched-like nanowire heterostructures and core-shell nanowire structures adopted to enhance the performance of nanowire-based chemical sensor are presented in detail
Materials Engineering Strategies to Control Metal Oxides Nanowires Sensing Properties
No full textMetal oxides (MOXs), in the form of nanowires, have proved to be an excellent active sensing layer of chemoresistive sensors due to their unique physical/chemical properties such as single crystallinity, exceptional electrical properties, and so on. Indeed, MOXs nanowires-based gas sensors show fast dynamic response with excellent reproducibility, stability, and reactivity toward various gas analytes. However, their limited selectivity and high operation temperature that lead to high power consumption are still major issues that need to be addressed. To improve these characteristics, researchers nowadays are working in the direction of modifying nanowires with different strategies. These strategies include nanowires heterostructures, decoration with particles (metals and metal oxides), core–shell structures, and surface functionalization with self-assembled monolayers and modification with graphene (pristine and oxidized). By employing these strategies, nanowires sensing performances, especially their selectivity, sensitivity, and response, can immensely enhance. Hence, in this review article, the above-mentioned strategies to improve the sensing performance of MOXs nanowires are reviewed. Attention is paid to underlying sensing mechanisms and improved sensing characteristics. In addition, MOXs gas sensing mechanism, working principle of conductometric gas sensors, and different synthesis techniques, used to modify nanowires, are also briefly discussed
Editorial: Oxytocin in brain health and disease: how can it exert such pleiotropic neuromodulatory effects?
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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
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