Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Limiting the Oxidation of WS2 Nanostructures by Oleylamine Surface Passivation for Room Temperature NH3 Sensing

Version 1 : Received: 5 August 2020 / Approved: 6 August 2020 / Online: 6 August 2020 (10:17:35 CEST)

How to cite: Gqoba, S.; Rodrigues, R.; Mphahlele, S.L.; Ndala, Z.; Airo, M.; Kolokoto, T.; Hümmelgen, I.A.; Linganiso, C.E.; Moloto, M.J.; Moloto, N. Limiting the Oxidation of WS2 Nanostructures by Oleylamine Surface Passivation for Room Temperature NH3 Sensing. Preprints 2020, 2020080150 (doi: 10.20944/preprints202008.0150.v1). Gqoba, S.; Rodrigues, R.; Mphahlele, S.L.; Ndala, Z.; Airo, M.; Kolokoto, T.; Hümmelgen, I.A.; Linganiso, C.E.; Moloto, M.J.; Moloto, N. Limiting the Oxidation of WS2 Nanostructures by Oleylamine Surface Passivation for Room Temperature NH3 Sensing. Preprints 2020, 2020080150 (doi: 10.20944/preprints202008.0150.v1).

Abstract

Oleylamine capped WS2 nanostructures were successfully formed at 320 °C via a relatively simple colloidal route. SEM and TEM analyses showed that the 3D nanoflowers that were initially formed disintegrated into 2D nanosheets after prolonged incubation. XPS and XRD analyses confirmed oxidation of WS2 into WO3. Sensors based on these oleylamine capped WS2 nanoflowers and nanosheets still showed a change in electrical response towards various concentrations of NH3 vapour at room temperature in a 25% relative humidity background despite the oxidation. The nanoflowers exhibited n-type response while the nanosheets displayed a p-type response towards NH3 exposure. The nanoflower based sensors showed better response to NH3 vapour exposure than the nanosheets. The sensors showed a good selectivity towards NH3 relative to acetone, ethanol, chloroform and toluene. Meanwhile, a strong interference of humidity to the NH3 response was displayed at high relative humidity levels. The results demonstrated that oleylamine limited the extent of oxidation of WS2 nanostructures. The superior sensing performance of the nanoflowers can be attributed to their hierarchical morphology which enhances the surface area and diffusion of the analyte.

Subject Areas

oleylamine; WS2; nanoflowers; gas sensing

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