Influence of exposure time and bias voltage on the response kinetics of toluene vapour on Ho3+-doped NiO chemiresistive sensors: Yellow-emitter nanophosphors

T. P. Mokoena*, H. C. Swart, T. A. Nhlapo, S. J. Mofokeng, T. D. Malevu, M. R. Mhlongo, D. E. Motaung

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

The incorporation of rare earths (REs) into semiconducting metal oxides is advantageous for creating surface defects and manipulating electronic structures. Therefore, the hydrothermal method fabricated p-type NiO nanostructures with various holmium (Ho3+) ion concentrations of 0, 1, 2, 3, and 4 wt% are investigated. The gas sensing features of the Ho3+-doped NiO sensors were conducted at different bias voltages and exposure times. At the bias voltage of 1 V with the exposure time of 5 min, the Ho3+-doped NiO sensors displayed a relatively high response of 36.35%, detection limit and sensitivity of 449 ppb and 0.749 ppm−1, respectively towards 60 ppm toluene at 100 °C. Upon increasing the exposure time to 1 h, at the applied bias voltage of 0.5 V, the response improved by almost 6 times (Rg/Ra ∼ 201%) towards 60 ppm of toluene, showing the outstanding toluene selectivity against benzene, xylene, ethyl-benzene and acetone vapours. The gas sensing findings proved that an appropriate concentration of Ho3+ doping, exposure time and applied bias voltage have a significant influence on the sensing performances. Further tuning of these features could result in an improved sensing response. The increased sensing mechanism is assigned to the creation of oxygen vacancies.

Original languageEnglish
Article number111378
JournalInorganic Chemistry Communication
Volume158
DOIs
Publication statusPublished - Dec 2023

Keywords

  • Applied bias voltage
  • Exposure time
  • NiO
  • Rare earth doping
  • Toluene vapour

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