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    Nanotube- and nanowire-based sensors for air quality monitoring
    (01-01-2022)
    Rani, Sanju
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    This chapter focuses on gas nanosensors based on three nanostructured semiconductor systems, namely, silicon nanowires (SiNWs), carbon nanotubes (CNTs), and metal oxide nanowires (MONWs), for air quality monitoring. Gas sensors form an integral part of both modern technology and our daily lives with their presence around us for ensuring safety, detecting pollution, disease diagnosis, industrial process controls, etc. Although several technologies exist for the detection of gases, semiconductor-based resistive gas sensors offer a highly portable and energy-efficient design and compact instrumentation and have been in use for several decades. The interaction of gas molecules with semiconductor surfaces leads to a change in resistance/conductance through the exchange of charges; hence the quantity and type of gas can be predicted by analyzing the magnitude of resistance change. In this context nanostructures such as nanotubes and nanowires provide not only higher surface area for enhanced gas adsorption but also unidirectional charge transport for a better signal-to-noise ratio. Further, the design of an electronic nose using an assembly of gas-sensing arrays and the implementation of artificial intelligence/machine learning tools have also been outlined.
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    Publication
    Solid-Solution MXenes and Their Properties
    (01-01-2023)
    Khatun, Nasima
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    MXenes are relatively new additions to the two-dimensional (2D) materials category and have become the fastest-growing family among them. Coexistent to their unique and uncommon properties, such as high electrical conductivity, excellent hydrophilicity, and tailoring of surface functional groups, MXenes have found potential applications in a variety of fields, such as energy storage and conversion, electromagnetic interference shielding, sensors, biomedical devices, catalysis, and so on. The chemical formula of MXene is M n +1X n T x (M = transition metals, X = carbon and/or nitrogen, T x = surface terminated functional groups, and n = 1-4). In the solid solution MXenes, more than one element in M and X sites are randomly distributed in a single M n +1X n slab without forming any impurity phase. In this chapter, we systematically discussed the structures, compositions, and processing of each group of solid solution MXenes depending on their n value. The wide variety of M elements, carbon and/or nitrogen ratio, the overall compositions, and surface functional groups influence their properties. Significant changes in the electronic transport, optical, plasmonic, photothermal, mechanical, and magnetic properties are addressed with existing challenges. The chapter concludes with an outlook for future expansion of the solid solution MXenes.