Abstract
Nanostructured semiconducting metal oxides (SMOs) are among the most popular sensing materials for integration into resistive-type gas sensors owing to their low costs and high sensing performances. SMOs can be decorated or doped with noble metals to further enhance their gas sensing properties. Ag is one of the cheapest noble metals, and it is extensively used in the decoration or doping of SMOs to boost the overall gas-sensing performances of SMOs. In this review, we discussed the impact of Ag addition on the gas-sensing properties of nanostructured resistive-based gas sensors. Ag-decorated or -doped SMOs often exhibit better responsivities/selectivities at low sensing temperatures and shorter response times than those of their pristine counterparts. Herein, the focus was on the detection mechanism of SMO-based gas sensors in the presence of Ag. This review can provide insights for research on SMO-based gas sensors.
Highlights
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When the Ag-doped graphene sensor was exposed to H2S gas, H2S adsorbed on Ag rather than on C because Ag is less electronegative than C; the adsorption of H2S led to a possible dissociation of H2S, and SO2 and H2O were formed by the release of electrons (Figure 18)
We have examined the promising effects of Ag addition on the detection performances of chemiresistive gas sensors
Summary
In the area of SMOs-based gas sensors, there are many review papers [26,27,28,29,30,31,32,33,34,35]. The observed enhancement in the NO2 detection performance of ZnO nanoellipsoids after Ag loading was associated with the synergistic effects of the semiconductor composite and Ag. the improvement of the sensing response in the presence of Ag was linked to the increased electron utilization ratio and the decreased recombination rate of photogenerated electrons and holes due to the trapping of electrons in the Ag NPs during excitation. Organic/inorganic hybrid nanocomposites possess unique characteristics owing to the combined properties of polymers and SMOs. decoration with noble metals, including Ag, may enhance the unique characteristics of the hybrid materials because of the catalytic activity of Ag. Qin et al [84] reported the NH3-sensing properties of Ag-loaded polypyrrole@Si nanowire (Ppy@SiNW) core–shell structures (Figure 15). These factors caused higher response amplitudes at high ambient humidity [84]
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