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Photocatalytic and Gas Sensitive Multiwalled Carbon Nanotube/TiO2-ZnO and ZnO-TiO2 Composites Prepared by Atomic Layer Deposition

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Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Szent Gellért tér 4., H-1111 Budapest, Hungary
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Department of Physical Chemistry and Materials Science, Budapest University of Technology and Economics, P.O. Box 92, H-1521 Budapest, Hungary
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Institute for Technical Physics and Materials Science, Research Centre of Energy, Hungarian Academy of Sciences, Konkoly–Thege út 29–33., H-1121 Budapest, Hungary
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Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, Budafoki út 8., H-1111 Budapest, Hungary
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Department of Atomic Physics, Budapest University of Technology and Economics, Budafoki út 8., H-1111 Budapest, Hungary
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Department of Inorganic Chemistry, AGH University of Science and Technology, Mickiewicza 30., 30-059 Kraków, Poland
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ASM Microchemistry Oy, Pietari Kalmin katu 1F2, FI-00560 Helsinki, Finland
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Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
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Author to whom correspondence should be addressed.
Nanomaterials 2020, 10(2), 252; https://doi.org/10.3390/nano10020252
Received: 5 December 2019 / Revised: 14 January 2020 / Accepted: 23 January 2020 / Published: 31 January 2020

TiO2 and ZnO single and multilayers were deposited on hydroxyl functionalized multi-walled carbon nanotubes using atomic layer deposition. The bare carbon nanotubes and the resulting heterostructures were characterized by TG/DTA, Raman, XRD, SEM-EDX, XPS, TEM-EELS-SAED and low temperature nitrogen adsorption techniques, and their photocatalytic and gas sensing activities were also studied. The carbon nanotubes (CNTs) were uniformly covered with anatase TiO2 and wurtzite ZnO layers and with their combinations. In the photocatalytic degradation of methyl orange, the most beneficial structures are those where ZnO is the external layer, both in the case of single and double oxide layer covered CNTs (CNT-ZnO and CNT-TiO2-ZnO). The samples with multilayer oxides (CNT-ZnO-TiO2 and CNT-TiO2-ZnO) have lower catalytic activity due to their larger average densities, and consequently lower surface areas, compared to single oxide layer coated CNTs (CNT-ZnO and CNT-TiO2). In contrast, in gas sensing it is advantageous to have TiO2 as the outer layer. Since ZnO has higher conductivity, its gas sensing signals are lower when reacting with NH3 gas. The double oxide layer samples have higher resistivity, and hence a larger gas sensing response than their single oxide layer counterparts. View Full-Text
Keywords: carbon nanotubes; titanium dioxide; zinc oxide; atomic layer deposition; photocatalysis; gas sensing carbon nanotubes; titanium dioxide; zinc oxide; atomic layer deposition; photocatalysis; gas sensing
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Bakos, L.P.; Justh, N.; Moura da Silva Bezerra da Costa, U.C.; László, K.; Lábár, J.L.; Igricz, T.; Varga-Josepovits, K.; Pasierb, P.; Färm, E.; Ritala, M.; Leskelä, M.; Szilágyi, I.M. Photocatalytic and Gas Sensitive Multiwalled Carbon Nanotube/TiO2-ZnO and ZnO-TiO2 Composites Prepared by Atomic Layer Deposition. Nanomaterials 2020, 10, 252.

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