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Facile synthesis of titania nanowires by a hot filament method and conductometric measurement of their response to hydrogen sulfide gas.

Munz, M; Langridge, M T*; Devarepally, K K*; Cox, D C; Patel, P; Martin, N A; Vargha, G; Stolojan, V*; White, S; Currey, R J* (2013) Facile synthesis of titania nanowires by a hot filament method and conductometric measurement of their response to hydrogen sulfide gas. ACS Appl. Mater. Interfaces, 5 (4). pp. 1197-1205.

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Abstract

Titania nanostructures are of increasing interest for a variety of applications, including photovoltaics, water splitting, and chemical sensing. Owing to the photocatalytical properties of TiO2, chemical processes that occur at its surface can be exploited for highly efficient nanodevices. A facile and fast synthesis route has been explored that is free of catalysts or templates. An environmental scanning electron microscopy (ESEM) system was employed to grow titania nanowires (NWs) in a water vapor atmosphere (~1 mbar) and to monitor the growth in situ. In addition, the growth process was also demonstrated using a simple vacuum chamber. In both processes, a titanium filament was heated via the Joule effect and NWs were found to grow on its surface, as a result of thermal oxidation processes. A variety of nanostructures were observed across the filament, with morphologies changing with the wire temperature from the center to the end points. The longest NWs were obtained for temperatures between ~730 °C and 810°C. Typically, they have an approximate thickness of ~300 nm and lengths of up to a few micrometers. Cross sections prepared by focused-ion-beam milling revealed the presence of a porous layer beneath the NW clusters. This indicates that the growth of NWs is driven by oxidation-induced stresses in the subsurface region of the Ti filament and by enhanced diffusion along grain boundaries. To demonstrate the potential of titania NWs grown via the hot filament method, single NW devices were fabricated and used for conductometric sensing of hydrogen sulfide (H2S) gas. The NW electric resistance was found to decrease in the presence of H2S. Its variation can be explained in terms of the surface depletion model.

Item Type: Article
Keywords: Titania (TiO2) nanowires, Semiconductor nanostructures, Nanodevices, Nanosensors, Dry synthesis, Chemical vapour deposition (CVD), Hot filament, Diffusion, Grain boundaries, Oxidation, Compressive stress, Gas sensing, Hydrogen sulphide (H2S)
Subjects: Nanoscience
Nanoscience > Surface and Nanoanalysis
Identification number/DOI: 10.1021/am302655j
Last Modified: 02 Feb 2018 13:14
URI: http://eprintspublications.npl.co.uk/id/eprint/5752

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