1,721,214 research outputs found
Metal oxides nanowires chemical/gas sensors: recent advances
Full text linkChemical/gas sensors are playing and will play a crucial role in smart building, smart houses, environmental monitoring, food quality monitoring and in the customization of personalized medicine, as they allow a constant data collection to monitor all the parameters needed for a preventive intervention related to health and wealth of human beings together with the environment. Nanowires (NWs) and NW-based heterostructures thanks to their peculiar properties such as high crystallinity, flexibility, conductivity, and optical activity are key components of future sensing devices. Notwithstanding a rapid growth in smart, portable, and wearable chemical sensing devices, the development of reliable devices for the detection of chemicals, gases, and vapors is still needed together with the possibility to correlate the sensing data with health and wealth of the analyzed system: food, environment, and human beings. In this short review, I am going to report few recent studies and achievements devoted to increase the functional performances of chemical sensing devices, keeping the focus on materials, sensing transduction, and data extraction/evaluation
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
Growth Processing and Strategies: A Way to Improve the Gas Sensing Performance of Nickel Oxide-Based Devices
No full textThe review paper provides a comprehensive analysis of nickel oxide (NiO) as an emerging material in environmental monitoring by surveying recent developments primarily within the last three years and reports the growth processing and strategies employed to enhance NiO sensing performance. It covers synthesis methods for pristine NiO, including vapor-phase, liquid-phase, and solution-processing techniques, highlighting advantages and limitations. The growth mechanisms of NiO nanostructures are explored, with a focus on the most recent research studies. Additionally, different strategies to improve the gas sensing performance of NiO are discussed (i.e., surface functionalization by metallic nanoparticles, heterostructure formation, carbon-based nanomaterials, and conducting polymers). The influence of these strategies on selectivity, sensitivity, response time, and stability of NiO-based sensors is thoroughly examined. Finally, the challenges and future directions that may lead to the successful development of highly efficient NiO-based gas sensors for environmental monitoring are introduced in this review
Solid oxide fuel cell: Decade of progress, future perspectives and challenges
No full textIn an increasing demand of renewable energy resources, fuel cell represents the highly efficient, clean and sustainable energy conversion source. Broadly speaking, fuel cell can be divided into six different categories according to the types of electrolyte and fuels used. Each type of fuel cells has their own advantages and disadvantages. Among them, solid oxide fuel cell (SOFC) gains significant attentions due to their high efficiency, cost-effectiveness and the possibility to utilize variety of fuels other than hydrogen such as hydrocarbons, coal gas etc. As name implies, SOFC uses solid electrolyte for their operation. Indeed, in medium and large power requirement sectors, SOFC are highly suitable. In the present review article, recent advances and future perspectives of SOFC have been discussed via reviewing the literature over last five years. Most of the available review articles discussed the literature in terms of specific SOFC component such as anode, cathode, electrolytes and so on. In contrast, herein the literatures have been reviewed in the context of two types of SOFC stack designs i.e. planar and tubular that have been immensely used to fabricate efficient SOFC devices. Furthermore, fundamental of SOFC operation and its typical I–V characteristics and SOFC designs are also discussed in detail. Furthermore, preparation techniques for planar and tubular SOFC are briefly described. Finally, some of the recent trends in SOFC technology along with challenges and future perspectives are presented in this review article
Mesoporous polycrystalline SnO2 framework synthesized by direct soft templating method for highly selective detection of NO2
No full textSnO2 is one of the most studied oxide materials for gas sensing applications. Investigations have shown that SnO2 is sensitive to a wide range of gaseous compounds. However, its lack of selectivity remains an issue. Here, a mesoporous polycrystalline SnO2 framework was successfully synthesized using a soft templating method at ambient temperature and pressure. The prepared materials were characterized using X-ray diffraction analysis, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, N2 sorption tests, and X-ray photoelectron spectroscopy. Gas sensing analyses were performed on two batches of the material calcined at 400 °C and 500 °C. The resultant materials were highly conductive at relatively low operating temperatures. The thermal annealing and operating temperatures of the materials had significant effects on their gas sensing response and selectivity. The structure calcined at 400 °C showed a very selective response of 407 to 1 ppm NO2. The superior sensing performance of the obtained mesoporous SnO2 framework is attributed to its small crystal size of 4-5 nm-less than double the thickness of the critical electron depletion layer-as well as its high surface area of 89 m2 g-1 and high pore volume of 0.12 cm3 g-
NiO-GDC nanowire anodes for SOFCs: novel growth, characterization and cell performance
No full textA solid-oxide fuel cell (SOFC) is a sustainable energy resource that has been efficiently used for large-scale applications such as gas-turbines. However, its miniaturization for small-scale applications requires novel electrode materials especially anodes (other than Ni-YSZ) in different configurations and designs such as in the nanostructure form. Herein, we are proposing the growth of a novel nickel oxide-gadolinium doped ceria (NiO-GDC) nanowire-based anode using a vapor-liquid-solid (VLS) mechanism. To the best of our knowledge, NiO-GDC has never been grown before in the form of nanowires using the VLS mechanism. The nanowires are prepared at different evaporation temperatures and exhibit dense morphology. Detailed Raman spectroscopy reveals that during the growth, reorganization of NiO-GDC particles results in the formation of a more complex structure that diverges from pristine NiO-GDC powder. Furthermore, the temperature-dependence of the electrical conductivity reveals that the nanowires prepared at 1400 degrees C (evaporation temperature) possess high conductivity due to better charge-carrier transport, confirmed by their low activation energies. The electrolyte-supported button cell synthesized using a NiO-GDC nanowire anode exhibits a maximum power density of similar to 178 mW cm(-2) at 800 degrees C and concentration polarization is found to be the major loss, as revealed by electrochemical impedance spectroscopy (EIS) data. Based on our preliminary investigations, these nanowires have great potential to be used as an anode for SOFCs
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
Recent Advances in Low-Dimensional Metal Oxides via Sol-Gel Method for Gas Detection
No full textLow-dimensional metal oxides have drawn significant attention across various scientific domains due to their multifaceted applications, particularly in the field of environment monitoring. Their popularity is attributed to a constellation of unique properties, including their high surface area, robust chemical stability, and remarkable electrical conductivity, among others, which allow them to be a good candidate for detecting CO, CO2, H2, NH3, NO2, CH4, H2S, and volatile organic compound gases. In recent years, the Sol-Gel method has emerged as a powerful and versatile technique for the controlled synthesis of low-dimensional metal oxide materials with diverse morphologies tailored for gas sensing applications. This review delves into the manifold facets of the Sol-Gel processing of metal oxides and reports their derived morphologies and remarkable gas-sensing properties. We comprehensively examine the synthesis conditions and critical parameters governing the formation of distinct morphologies, including nanoparticles, nanowires, nanorods, and hierarchical nanostructures. Furthermore, we provide insights into the fundamental principles underpinning the gas-sensing mechanisms of these materials. Notably, we assess the influence of morphology on gas-sensing performance, highlighting the pivotal role it plays in achieving exceptional sensitivity, selectivity, and response kinetics. Additionally, we highlight the impact of doping and composite formation on improving the sensitivity of pure metal oxides and reducing their operation temperature. A discussion of recent advances and emerging trends in the field is also presented, shedding light on the potential of Sol-Gel-derived nanostructures to revolutionize the landscape of gas sensing technologies
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