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Highly Selective NO2 Gas Sensors made of MWCNTs and WO3 Hybrid Layers
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2007 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 154, no 5, J141-J149 p.Article in journal (Refereed) Published
Abstract [en]

Hybrid gas sensors were fabricated by means of multiwalled carbon nanotubes (MWCNTs) covered by W O3 deposited by an advanced reactive gas deposition method. In order to increase the dispersion of nanotubes and attach functional groups to their surface so as to enhance their compatibility with other compounds, the MWCNTs were functionalized in two different radio-frequency plasmas (oxygen or hydrogen) under different operating conditions. X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy were employed to analyze the composition and morphology of the hybrid films. Gas sensors based on such films were found to be very selective to N O2 when operated at room temperature. No cross-sensitivity was found to other hazardous gases such as N H3 or CO.

Place, publisher, year, edition, pages
2007. Vol. 154, no 5, J141-J149 p.
Keyword [en]
carbon nanotubes, tungsten compounds, thin films, gas sensors, sputter deposition, X-ray photoelectron spectra, scanning electron microscopy, atomic force microscopy
National Category
Engineering and Technology
URN: urn:nbn:se:uu:diva-14397DOI: 10.1149/1.2667855ISI: 000245371700055OAI: oai:DiVA.org:uu-14397DiVA: diva2:42167
Available from: 2008-01-30 Created: 2008-01-30 Last updated: 2016-04-11Bibliographically approved
In thesis
1. Nanostructured Transition Metal Oxides in Cleantech Application: Gas Sensors, Photocatalysis, Self-cleaning Surfaces Based on TiO2, WO3 and NiO
Open this publication in new window or tab >>Nanostructured Transition Metal Oxides in Cleantech Application: Gas Sensors, Photocatalysis, Self-cleaning Surfaces Based on TiO2, WO3 and NiO
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis focuses on the application of nanocrystalline transition metal oxide TiO2, WO3 and NiO thin films in new “green” building technologies. Specifically, their physicochemical properties in photocatalytic, self-cleaning and gas sensing applications are studied. There is an intimate connection between comfort issues, health, with connections to energy efficiency, leading to a need for intelligent building materials and green architecture. The importance of good indoor environment is augmented by the fact that modern man in developed countries spends some 90 % of his time inside buildings and vehicles. Poor air quality may lead to discomfort of the person inhabiting a building and in ultimately cause adverse health effects.

Thin films of nanocrystalline TiO2 were prepared using reactive DC magnetron sputtering. Crystalline mesoporous films of WO3 and NiO were prepared using advanced gas deposition technique (AGD). The crystal structure, morphology, optical and chemical properties of the films were characterized by using grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM), UV/Vis spectroscopy and X-ray photoelectron spectroscopy (XPS), respectively. The photocatalytic properties and adsorption of both organic and inorganic molecules on pure and functionalized films were probed by in situ Fourier transform infrared spectroscopy (FTIR). The gas sensing properties of sensors based on TiO2, WO3 and NiO were investigated by conductivity measurements and noise spectroscopy.

It was found for the first time that NiO based thin film sensors can be used to detect H2S and NO2 at low temperatures – down to room temperature. Hybrid WO3 sensors functionalized with multiwalled carbon nanotubes (MWCNTs) were used to detect NO2, CO and NH3 gases. These hybrid gas sensors show improved recovery properties compared to unmodified WO3 sensors. TiO2 based gas sensors were able to detect low concentrations of H2S by noise spectroscopy provided that the sensors were irradiated by UV light. Furthermore we show that sulphur is photo-fixated in crystalline TiO2 films upon simultaneous SO2 gas exposure and UV irradiation. Studies of the kinetics and identity of the photo-fixated sulphur complexes show that these are formed by photo-induced reactions between oxygen and SO2 at oxygen surface vacancy sites in TiO2. The sulphur modified TiO2 films show interesting self-cleaning properties compared to the pure films.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 69 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 809
Gas sensing, Self-cleaning, photo-fixation, photocatalysis, TiO2, WO3, NiO
National Category
Manufacturing, Surface and Joining Technology Other Materials Engineering
Research subject
Engineering Science with specialization in Solid State Physics
urn:nbn:se:uu:diva-148872 (URN)978-91-554-8026-4 (ISBN)
Public defence
2011-03-25, Häggsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 739Available from: 2011-03-17 Created: 2011-03-11 Last updated: 2011-05-04

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Topalian, ZarehGranqvist, Claes G.
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