1,721,007 research outputs found
“Quantum dots: Perspectives in next-generation chemical gas sensors” ‒ A review
No full textAdvances in gas sensing devices are urgently needed to reduce air pollution and control human health. In this regard, the progress in the development of low-dimensional semiconductor structures may revolutionize the concept of conventional gas sensors. The confinement of charge carriers in one or more spatial dimensions leads to the unique electrical and optical properties of semiconductor materials. Quantum dots, where the electron-hole pairs are confined in all three dimensions, offer new insights into the properties of materials. The research on quantum dot chemical sensors has become one of the rapidly developing fields in contemporary sensing technologies. The structures comprising quantum dots have shown promising sensing performance indicating that they are emerging as a new class of materials for application in chemiresistive devices. However, the QD-based structures are only beginning to be integrated into the monitoring systems. The experimental findings suggest that intensive studies need to be performed for deeply understanding the influence of synthesis procedures and additive materials on the sensing performance of quantum dots. Moreover, the response and selectivity of the materials should be analyzed considering the band gap changes in quantum dots as the size is varied. This paper provides an overview of the progress in the research of semiconductor quantum dots for application in chemical gas sensors. Advances in the fabrication and functionalities of metal oxide, chalcogenide and carbon quantum dots are highlighted. The effect of precursor materials and preparation methods on the structural features, chemical nature, size reduction and electronic properties of quantum dots are considered to examine their sensing performance. Afterward, a brief summary and outlook for the field are provided, along with the achievements and issues that are important for future studies
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-
Anodic TiO2 nanotubes: A promising material for energy conversion and storage
No full textSelf-organized TiO2 nanotube (TNT) layers formed by an anodization process have emerged for the conception of innovative systems in the conversion and storage of energy. Herein, the latest progress in power sources with a remarkable electrochemical performance involving these versatile nanomaterials is reported. Besides the key role of their physico-chemical properties, the significance of interfaces established with other materials to achieve the fabrication of batteries, supercapacitors and fuel cells showing high electrochemical performance is also high-lighted. Particularly, recent approaches based on the chemical modifications of the TNTs by doping, solid-state reactions, atomic layer deposition, electrodeposition of metallic nanoparticles and copolymers are presented. In addition, the strong potential offered by TNT layers for future research works is discussed. This progress report seeks to demonstrate the strong input of anodic TNT layers for developing the next generation of autonomous devices while stimulating more research efforts dedicated to modern technological applications
Fabrication of TiO2 and TiO2<Nb> Nanotubular Arrays and Their Gas Sensing Properties
No full textAbstractPure TiO2 and TiO2<Nb> nanotubular arrays were successfully sensitized. Nanotubular arrays were prepared by electrochemical anodization of thin films of Ti and of Ti-Nb deposited on alumina substrates with two different roughness. Morphological characterization and functional properties are presented. The gas sensing properties of TiO2 and TiO2<Nb> nanotubes with different gases have been tested in a wide range of operating temperatures
Efficient one-pot synthesis of antimony-containing mesoporous tin dioxide nanostructures for gas-sensing applications
No full textGraphene oxide and its chemical nature: Multi-stage interactions between the oxygen and graphene
No full textIn this paper, we have comprehensively reviewed the results of recent studies on novel unique material, which is a product of oxidation of graphene or graphite and generally known as graphene oxide. The main focus has been to perform critical analysis and understand whether a monomolecular layer of graphene with attached oxygen atoms and/or various oxygen-containing functional groups (epoxy, carbonyl, carboxyl or hydroxyl) can be considered as an independent phase of a substance, i.e. an oxide. The arguments towards the verification of multi-stage interactions between the oxygen and graphene have been highlighted. The definition of graphene oxide has been analyzed considering proposed structure models, approaches utilized for its preparation, properties of graphene-based materials and their applications in advanced microanalytical platforms, environmental security systems, biosensors and chips for mass spectrometry. Moreover, to support the discussions on the pros and cons, we carried out analyses of the graphene oxide-based material in our laboratory and provided the experimental findings. The chemical nature of the combined structure of oxygen-containing functional groups and a single-layer of carbon atoms is of particular importance in the physical chemistry of surfaces and dispersion systems. Thus, this review is expected to improve a modern understanding of the surface chemistry of nanomaterials and also will provide an opportunity to better analyze the stability of their properties that will be important in many application fields, including the development of micro- and nano-devices based on the modified graphene
Progress towards chemical gas sensors: Nanowires and 2D semiconductors
No full textThere is a great interest in portable gas sensing technologies to provide real-time monitoring of indoor and outdoor air quality as well as the human health diagnostics. One-dimensional metal oxide nanowires have demonstrated improved properties compared to the conventional thick film gas sensors. Furthermore, two-dimensional semiconductor nanomaterials have shown great promise for the development of high performance functional devices owing to their unique physical, chemical and electrical characteristics. Hence, they become one of the most investigated structures for the fabrication of detection systems. Herein, we present an overview of the synthesis and sensing properties of metal oxide nanowires and two-dimensional semiconductor nanostructures such as metal-organic frameworks, graphene and transition metal dichalcogenides. We discuss the current achievements and issues in the preparation of pure, doped and composite materials comprising metal oxide nanowires and two-dimensional semiconductors. Then, we discuss the advances in gas sensing performances of the aforementioned materials considering their morphology, compositions and structure. Afterward, we provide a brief summary along with the opportunities and challenges for future fabrication of high performance and small size gas sensing devices
Quality Evaluation of Parmigiano Reggiano Cheese by a Novel Nanowire Device S3 and Evaluation of the VOCs Profile
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