Abstract
In this work, the main objective is to enhance the gas sensing capability through investigating the effect of Al and Mg doping on ZnO based sensors. ZnO, Mg1% doped ZnO, Al5% doped ZnO and (Al5%, Mg1%) co-doped ZnO nanoparticles (NPs) were synthesized by a modified sol-gel method. The structural characterization showed the hexagonal crystalline structure of the prepared samples. Morphological characterizations confirmed the nanometric sizes of the NPs (27–57 nm) and elemental composition investigation proved the existence of Al and Mg with low concentrations. The optical characterization showed the high absorbance of the synthesized samples in the UV range. The gas sensing performances of the synthesized samples, prepared in the form of thick films, were investigated. Sensing tests demonstrated the high influence of the Al and Mg on the sensing performances towards H2 and CO gas, respectively. The 5A1MZO-based sensor exhibits high sensitivity and low detection limits to H2 (<2 ppm) and CO (<1 ppm). It showed a response around 70 (at 250 °C) towards 2000 ppm H2 and 2 (at 250 °C) towards CO.
Highlights
We have reported in our previous work [26] a considerable improvement in formaldehyde sensing of Ca-doped ZnO NPs-based sensor due to the basic centers provided by calcium which induces high gas adsorption
Carbon monoxide (CO) is an odorless, colorless, flammable and toxic gas which is produced by fossil fuel combustion, automotive emissions, industrial activities and household fuel-based devices
After that, when a reducing gas such as H2 or CO is injected into the chamber, the gas molecules react with the oxygen anion and release the trapped electrons back to the of 17 conduction band
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Various materials such as graphene, polymers, small organic materials and semiconductor oxides are used for the sensitive detection of certain reducing gases [12,13]. This induces the release of free electrons and contributes to high conductivity in ZnO material [28] In this context, we have reported in our previous work [26] a considerable improvement in formaldehyde sensing of Ca-doped ZnO NPs-based sensor due to the basic centers provided by calcium which induces high gas adsorption. The Ga doped ZnO-based sensor showed a capacity to detect low CO concentrations at relatively lower operating temperature (200 ◦ C). It showed higher sensitivity and faster response/recovery times compared to pure ZnO sensor.
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