title: Hybridization of Zinc Oxide Tetrapods for Selective Gas Sensing Applications.
abstract: In this work, the exceptionally improved sensing capability of highly porous three-dimensional (3-D) hybrid ceramic networks toward reducing gases is demonstrated for the first time. The 3-D hybrid ceramic networks are based on doped metal oxides (MexOyand ZnxMe1-xOy, Me = Fe, Cu, Al) and alloyed zinc oxide tetrapods (ZnO-T) forming numerous junctions and heterojunctions. A change in morphology of the samples and formation of different complex microstructures is achieved by mixing the metallic (Fe, Cu, Al) microparticles with ZnO-T grown by the flame transport synthesis (FTS) in different weight ratios (ZnO-T:Me, e.g., 20:1) followed by subsequent thermal annealing in air. The gas sensing studies reveal the possibility to control and change/tune the selectivity of the materials, depending on the elemental content ratio and the type of added metal oxide in the 3-D ZnO-T hybrid networks. While pristine ZnO-T networks showed a good response to H2gas, a change/tune in selectivity to ethanol vapor with a decrease in optimal operating temperature was observed in the networks hybridized with Fe-oxide and Cu-oxide. In the case of hybridization with ZnAl2O4, an improvement of H2gas response (to ∼7.5) was reached at lower doping concentrations (20:1), whereas the increase in concentration of ZnAl2O4(ZnO-T:Al, 10:1), the selectivity changes to methane CH4gas (response is about 28). Selectivity tuning to different gases is attributed to the catalytic properties of the metal oxides after hybridization, while the gas sensitivity improvement is mainly associated with additional modulation of the electrical resistance by the built-in potential barriers between n-n and n-p heterojunctions, during adsorption and desorption of gaseous species. Density functional theory based calculations provided the mechanistic insights into the interactions between different hybrid networks and gas molecules to support the experimentally observed results. The studied networked materials and sensor structures performances would provide particular advantages in the field of fundamental research, applied physics studies, and industrial and ecological applications.
authors.affiliation: Functional Nanomaterials, Institute for Materials Science, Kiel University , Kaiserstrasse 2, D-24143, Kiel, Germany.|Department of Microelectronics and Biomedical Engineering, Technical University of Moldova , 168 Stefan cel Mare Avenue, MD-2004 Chisinau, Republic of Moldova.
authors.forename: O
authors.identifier: http://orcid.org/0000-0002-7913-9712
authors.initials: O
authors.lastname: Lupan
authors.affiliation: Department of Microelectronics and Biomedical Engineering, Technical University of Moldova , 168 Stefan cel Mare Avenue, MD-2004 Chisinau, Republic of Moldova.
authors.forename: V
authors.initials: V
authors.lastname: Postica
authors.affiliation: Functional Nanomaterials, Institute for Materials Science, Kiel University , Kaiserstrasse 2, D-24143, Kiel, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Gröttrup
authors.affiliation: Department of Chemistry, University College London , 20 Gordon Street, London WC1H 0AJ, United Kingdom.|Research & Development, University of Petroleum and Energy Studies (UPES) , Bidholi, Dehradun 248007, India.
authors.forename: A K
authors.initials: AK
authors.lastname: Mishra
authors.affiliation: Department of Chemistry, University College London , 20 Gordon Street, London WC1H 0AJ, United Kingdom.|School of Chemistry, Cardiff University , Main Building, Park Place, Cardiff CF10 3AT, United Kingdom.
authors.forename: N H
authors.initials: NH
authors.lastname: de Leeuw
authors.affiliation: Department of Physics and I3N, Institute for Nanostructures, Nanomodelling and Nanofabrication, University of Aveiro , 3810-193 Aveiro, Portugal.
authors.forename: J F C
authors.initials: JF
authors.lastname: Carreira
authors.affiliation: Department of Physics and I3N, Institute for Nanostructures, Nanomodelling and Nanofabrication, University of Aveiro , 3810-193 Aveiro, Portugal.
authors.forename: J
authors.initials: J
authors.lastname: Rodrigues
authors.affiliation: Department of Physics and I3N, Institute for Nanostructures, Nanomodelling and Nanofabrication, University of Aveiro , 3810-193 Aveiro, Portugal.
authors.forename: N
authors.initials: N
authors.lastname: Ben Sedrine
authors.affiliation: Department of Physics and I3N, Institute for Nanostructures, Nanomodelling and Nanofabrication, University of Aveiro , 3810-193 Aveiro, Portugal.
authors.forename: M R
authors.initials: MR
authors.lastname: Correia
authors.affiliation: Department of Physics and I3N, Institute for Nanostructures, Nanomodelling and Nanofabrication, University of Aveiro , 3810-193 Aveiro, Portugal.
authors.forename: T
authors.identifier: http://orcid.org/0000-0001-6945-2759
authors.initials: T
authors.lastname: Monteiro
authors.affiliation: Department of Microelectronics and Biomedical Engineering, Technical University of Moldova , 168 Stefan cel Mare Avenue, MD-2004 Chisinau, Republic of Moldova.
authors.forename: V
authors.initials: V
authors.lastname: Cretu
authors.affiliation: Department of Microelectronics and Biomedical Engineering, Technical University of Moldova , 168 Stefan cel Mare Avenue, MD-2004 Chisinau, Republic of Moldova.
authors.forename: I
authors.initials: I
authors.lastname: Tiginyanu
authors.affiliation: Functional Nanomaterials, Institute for Materials Science, Kiel University , Kaiserstrasse 2, D-24143, Kiel, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Smazna
authors.affiliation: Functional Nanomaterials, Institute for Materials Science, Kiel University , Kaiserstrasse 2, D-24143, Kiel, Germany.
authors.forename: Y K
authors.identifier: http://orcid.org/0000-0002-8786-9379
authors.initials: YK
authors.lastname: Mishra
authors.affiliation: Functional Nanomaterials, Institute for Materials Science, Kiel University , Kaiserstrasse 2, D-24143, Kiel, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Adelung
keywords: CH4 gas; DFT study; ZnO tetrapod; gas sensor; hybrid; hydrogen sensor; optical studies; selectivity