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Hybridization of zinc oxide tetrapods for selective gas sensing applications

Lupan, O., Postica, V, Gröttrup, J, Mishra, A K, de Leeuw, Nora H, Carreira, J F C, Rodrigues, J, Sedrine, N Ben, Correia, Maria R, Monteiro, Teresa, Cretu, V, Tiginyanu, I, Smazna, Daria, Mishra, Y K and Adelung, R 2017. Hybridization of zinc oxide tetrapods for selective gas sensing applications. ACS Applied Materials & Interfaces 9 (4) , pp. 4084-4099. 10.1021/acsami.6b11337

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In this work, the exceptionally improved sensing capability of highly porous 3-D hybrid ceramic networks with respect to reducing gases is demonstrated for the first time. The 3-D hybrid ceramic networks are based on metal oxides (MexOy and ZnxMe1-xOy, Me= Fe, Cu, Al) doped and alloyed zinc oxide tetrapods (ZnO-T) forming numerous 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 tetrapods grown by flame transport synthesis (FTS) approach with different weight ratios (ZnO:Me, e.g., 20:1) and followed by subsequent thermal annealing them 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 the added metal oxide in 3-D ZnO-T hybrid networks. While pristine ZnO-T networks showed a good response to H2 gas, a change/tune in selectivity to ethanol vapour with a decrease in optimal operating temperature was observed in the networks hybridized with Fe-oxide and Cu-oxide. In case of hybridization with ZnAl2O4 an improvement of H2 gas response (to ≈ 7.5) was reached at lower doping concentrations (20:1), whereas the increasing in concentration of ZnAl2O4 (10:1), the selectivity changes to methane CH4 gas (response ≈ 28). Selectivity tuning to different gases is attributed to the catalytic properties of the metal oxides after hybridization, while the sensitivity improvement is mainly associated with additional modulation of 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 supporting the experimentally observed results. The studied materials and sensor structures would provide particular advantages in the field of fundamental research, industrial and ecological applications.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Uncontrolled Keywords: CH4 gas; DFT study; gas sensor; hybrid; hydrogen sensor; optical studies; selectivity; ZnO tetrapod
Publisher: American Chemical Society
ISSN: 1944-8244
Date of First Compliant Deposit: 10 February 2017
Date of Acceptance: 30 December 2016
Last Modified: 24 Jan 2018 09:48

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