Facile control of room temperature nitrogen dioxide gas selectivity induced by copper oxide nanoplatelets

D N Oosthuizen; Ioannis Korditis; H C Swart; D E Motaung

doi:10.1016/j.jcis.2019.10.036

Facile control of room temperature nitrogen dioxide gas selectivity induced by copper oxide nanoplatelets

J Colloid Interface Sci. 2020 Feb 15:560:755-768. doi: 10.1016/j.jcis.2019.10.036. Epub 2019 Oct 13.

Authors

D N Oosthuizen¹, Ioannis Korditis², H C Swart³, D E Motaung⁴

Affiliations

¹ Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA9300, South Africa; DST/CSIR National Centre for Nano-structured Materials, Council for Scientific Industrial Research, Pretoria ZA0001, South Africa. Electronic address: oosthuizendn@gmail.com.
² Department of Physics and Engineering, University of Zululand, Kwa-Dlangezwa, 3886, South Africa.
³ Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA9300, South Africa.
⁴ Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA9300, South Africa; Department of Physics, University of Limpopo, Private Bag X1106, Sovenga 0727, South Africa. Electronic address: david.motaung@ul.ac.za.

PMID: 31706648
DOI: 10.1016/j.jcis.2019.10.036

Abstract

Development of room-temperature operating gas sensors, utilizing p-type CuO nanoplatelets for air quality monitoring with excellent response, high sensitivity and good reliability, is highly desirable. Therefore, in this work, we investigated both the influence of synthesis reaction temperature and time on the sensitivity, selectivity, and response of CuO nanoplatelets prepared through the hydrothermal synthetic method, in the presence of NaOH as base, without the support of any surfactant. The gas sensing findings revealed that the CuO nanoplatelets NO₂ sensitivity and selectivity can be controlled and tuned by adjusting the synthesis reaction temperature and time, while maintaining the morphology. The CuO-based sensors revealed a remarkable response of 14.5 to 20 ppm NO₂, with a sensitivity of 0.47 ppm^-1 at room temperature. A decrease in sensing performance was observed at higher operating temperatures. The findings affirmed that such sensor response/sensitivity is not dependent on the specific surface area and is relatively interrelated to the adsorption sites, the average crystallite size, and low charge carrier concentration, giving rise to a more pronounced change in CuO sensor resistance. The influence of relative humidity (RH) was also investigated to have an understanding of the sensor performance in real testing conditions. Additionally, the stability analyses to four cycles of different humidity percentages and gas concentration-related repeatability conditions were carried out, and the sensor revealed a slight drifting when increasing the number of testing cycles.

Keywords: CuO; Humidity; NO(2) gas sensing; Temperature-dependent.