Abstract
A composite material based on carbon quantum dots (CQDs) and NiO was prepared and tested for methane sensing. The synthesis procedure is simple and foresees the preparation of the CQDs by citric acid pyrolysis and NiO by hydrothermal synthesis. A phase sonication and stirring procedure yielded the composite CQDs@NiO at different loads. The composites were characterized by X-ray diffraction, ultraviolet–visible light (UV–Vis) spectroscopy, SEM microscopy, energy-dispersive spectroscopy (EDS) mapping, and surface area, porosity, and impedance measurements. A gas sensor was built in-house and used to probe the response of the synthesized samples to CH4 detection, at constant environmental humidity. The CQDs@NiO at 1% weight load displayed excellent performances in terms of gas response both vs. temperature and vs. concentration, whereas higher loads resulted in CQD aggregation and diminished output. Response/recovery times of the 1%CQDs@NiO sample were good, as well as the selectivity and the stability over time and for variable environmental humidity. The estimated limit of detection was 0.1 ppm.
Highlights
Methane gas is extensively employed as fuel in houses and industries, and as a propellant for automotive vehicles [1,2,3]
The carbon quantum dots (CQDs)@NiO at 1% weight load displayed excellent performances in terms of gas response both vs. temperature and vs. concentration, whereas higher loads resulted in CQD aggregation and diminished output
Because of the odorless and flammable nature of this asphyxiant gas, the development of sensitive detectors for real-time detection at concentrations lower than its explosive limit is in pressing need
Summary
Methane gas is extensively employed as fuel in houses and industries, and as a propellant for automotive vehicles [1,2,3]. Low-cost fabrication of CH4 sensors is an asset in order to make such devices accessible to the general public In this framework, the ideal combination of sensors properties includes sensitivity, quick response, low-cost sensing material and sensor components. It must be added that, for other gases such as CO2 , potentiometric sensors were developed, without a need for trapping in liquid, albeit working at high temperatures and requiring a BaCO3 layer for limiting the humidity interference [16] Under these premises, we designed and probed a low-cost material to insert in a home-assembled sensor, built with an available set of components, for high-sensitivity CH4 detection. We opted for NiO as a substrate, because of its good sensing
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