Highly selective NH3 gas sensor based on Au loaded ZnO nanostructures prepared using microwave-assisted method

K Shingange; Z P Tshabalala; O M Ntwaeaborwa; D E Motaung; G H Mhlongo

doi:10.1016/j.jcis.2016.06.046

Highly selective NH3 gas sensor based on Au loaded ZnO nanostructures prepared using microwave-assisted method

J Colloid Interface Sci. 2016 Oct 1:479:127-138. doi: 10.1016/j.jcis.2016.06.046. Epub 2016 Jun 25.

Authors

K Shingange¹, Z P Tshabalala¹, O M Ntwaeaborwa², D E Motaung³, G H Mhlongo⁴

Affiliations

¹ DST/CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, Pretoria 0001, South Africa; Department of Physics, University of the Free State, Bloemfontein 9300, South Africa.
² Department of Physics, University of the Free State, Bloemfontein 9300, South Africa.
³ DST/CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, Pretoria 0001, South Africa. Electronic address: dmotaung@csir.co.za.
⁴ DST/CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, Pretoria 0001, South Africa. Electronic address: gmhlongo@csir.co.za.

PMID: 27388126
DOI: 10.1016/j.jcis.2016.06.046

Abstract

ZnO nanorods synthesized using microwave-assisted approach were functionalized with gold (Au) nanoparticles. The Au coverage on the surface of the functionalized ZnO was controlled by adjusting the concentration of the Au precursor. According to X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) results, it was confirmed that Au form nanoparticles loaded on the surface of ZnO. The small Au loading level of 0.5wt% showed the highest response of 1600-100ppm of NH3 gas at room temperature (RT) whereas further increase of Au loading level resulted in poor detection of NH3. All Au loaded ZnO (Au/ZnO) based sensors exhibited very short recovery and response times compared to unloaded ZnO sensing materials. The responses of ZnO and Au/ZnO based sensors (0.5-2.5wt%) to other flammable gases, including H2, CO and CH4, were considerably less, demonstrating that Au/ZnO based sensors were highly selective to NH3 gas at room temperature. Spill over mechanism which is the main reason for the observed enhanced NH3 response with 0.5 Au loading level is explained in detail.

Keywords: Au nanoparticles loading; NH(3) gas sensors; ZnO nanorods.