High-Temperature Synthesis of Nickel-Based Nanoparticles for Use as Materials in Sensors of Potentially Hazardous Gases

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–The gas-sensing properties of nickel ferrite (NiFe₂O₄) and nickel oxide (NiO) nanoparticles prepared by a self-sustaining levitation-jet synthesis (LJS) method are reported. These have been compared to the gas-sensing properties of a NiO sensor prepared using a commercially sourced powder. The microstructure, surface area, particle size, and morphology varied widely across the sensors fabricated. It was anticipated that these contrasting properties would play a key role in either enhancing or worsening the sensing capabilities of the materials. Gases of interest included ethanol, toluene, and carbon monoxide as well as the gas response of the sensors was investigated at different operating temperatures. In general, the sensors responded to gases with different degrees of sensitivity. Among the sensors with higher surface areas, one provided noticeable enhancements in sensitivity towards gases when compared, for instance, to the sensitivity of the commercially based NiO sensor. The NiFe₂O₄ sensor presented most promise as a gas sensor to ethanol and, to a greater or lesser degree, towards toluene gas. In general, sensors were poorly responsive to the carbon monoxide concentrations tested. This study is one of the first reports of using LJS-based powders for gas sensing applications and it highlights the suitability of the method to fabricate size- and shape-controlled nanomaterials for the detection of environmentally relevant gases.