Scientific Results

Functionalised zinc oxide nanowire gas sensors: Enhanced NO2 gas sensor response by chemical modification of nanowire surfaces

Year: 2012

Authors: Waclawik E.R., Chang J., Ponzoni A., Concina I., Zappa D., Comini E., Motta N., Faglia G., Sberveglieri G.

Autors Affiliation: Queensland Univ Technol, Sch Chem Phys & Mech Engn, Brisbane, Qld 4000, Australia;
Univ Brescia, Dept Chem & Phys, I-25133 Brescia, Italy;
SENSOR Lab, CNR IDASC, I-25133 Brescia, Italy

Abstract: Surface coating with an organic self-assembled monolayer (SAM) can enhance surface reactions or the absorption of specific gases and hence improve the response of a metal oxide (MOx) sensor toward particular target gases in the environment. In this study the effect of an adsorbed organic layer on the dynamic response of zinc oxide nanowire gas sensors was investigated. The effect of ZnO surface functionalisation by two different organic molecules, tris(hydroxymethyl)aminomethane (THMA) and dodecanethiol (DT), was studied. The response towards ammonia, nitrous oxide and nitrogen dioxide was investigated for three sensor configurations, namely pure ZnO nanowires, organic-coated ZnO nanowires and ZnO nanowires covered with a sparse layer of organic-coated ZnO nanoparticles. Exposure of the nanowire sensors to the oxidising gas NO2 produced a significant and reproducible response. ZnO and THMA-coated ZnO nanowire sensors both readily detected NO2 down to a concentration in the very low ppm range. Notably, the THMA-coated nanowires consistently displayed a small, enhanced response to NO2 compared to uncoated ZnO nanowire sensors. At the lower concentration levels tested, ZnO nanowire sensors that were coated with THMA-capped ZnO nanoparticles were found to exhibit the greatest enhanced response. Delta R/R was two times greater than that for the as-prepared ZnO nanowire sensors. It is proposed that the Delta R/R enhancement in this case originates from the changes induced in the depletion-layer width of the ZnO nanoparticles that bridge ZnO nanowires resulting from THMA ligand binding to the surface of the particle coating. The heightened response and selectivity to the NO2 target are positive results arising from the coating of these ZnO nanowire sensors with organic-SAM-functionalised ZnO nanoparticles.


Volume: 3      Pages from: 368  to: 377

More Information: The authors acknowledge the financial support of the Queensland Government through the Queensland Smart State Futures Program NIRAP (National and International Research Alliances Program). ERW acknowledges the QUT Faculty of Science for financial support and the Queensland Government for a Queensland International Fellowship. JC gratefully acknowledges the China Scholarship Council for a PhD scholarship in pursuit of this work.
KeyWords: gas sensor; nanowire; tris( hydroxymethyl) aminomethane; self-assembled monolayer; zinc oxide
DOI: 10.3762/bjnano.3.43

Citations: 58
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