Abstract
Among various approaches to improve the sensing performance of metal oxide, the metal-doped method is perceived as effective, and has received great attention and is widely investigated. However, it is still a challenge to construct heterogeneous metal-doped metal oxide with an excellent sensing performance. In the present study, porous Pb-doped ZnO nanobelts were prepared by a simply partial cation exchange method, followed by in situ thermal oxidation. Detailed characterization confirmed that Pb was uniformly distributed on porous nanobelts. Additionally, it occupied the Zn situation, not forming its oxides. The gas-sensing measurements revealed that 0.61 at% Pb-doped ZnO porous nanobelts exhibited a selectively enhanced response with long-term stability toward n-butanol among the investigated VOCs. The relative response to 50 ppm of n-butanol was up to 47.7 at the working temperature of 300 °C. Additionally, the response time was short (about 5 s). These results were mainly ascribed to the porous nanostructure, two-dimensional belt-like morphology, enriched oxygen vacancies and the specific synergistic effect from the Pb dopant. Finally, a possible sensing mechanism of porous Pb-doped ZnO nanobelts is proposed and discussed.
Highlights
Academic Editor: Andrea PonzoniDue to the outstanding merits of low cost, easy fabrication, high-sensing performance and compatibility with modern electronic devices, resistive-type metal oxide semiconductor (MOS) gas sensors have been widely applied to detect VOCs in various fields, such as human health, environment monitoring, food processing and industrial manufacture.Compared with p-type oxide semiconductors, n-type oxide semiconductors have received more attention since the discovery of oxide semiconductor-based gas sensors in the 1960s, because of their special sensing mechanism and highly relative response [1–4]
The results show a fast response of the sensors and a stable value of response in the saturation region, which has a regular relationship with the concentration of n-butanol
For n-butanol, methanol and isopropanol, they are more than four, two and three times of those of the pristine ZnO porous nanobelts, respectively. This suggests that the sensing performance of ZnO porous nanobelts is greatly improved by the doping of Pb. This result manifested the high sensing selectivity of the 0.61 at% Pb-doped ZnO porous nanobelts toward n-butanol, which could be ascribed to the particular active interfaces from the doped Pb ions at the surfaces, and the synergistic effect between the molecular polarity of n-butanol and the polar surface provided by Pb. [41,52]
Summary
Due to the outstanding merits of low cost, easy fabrication, high-sensing performance and compatibility with modern electronic devices, resistive-type metal oxide semiconductor (MOS) gas sensors have been widely applied to detect VOCs in various fields, such as human health, environment monitoring, food processing and industrial manufacture. The technology of doping ions in MOSs was widely applied in the practical field of improving performance, which was responsible for forming oxygen vacancies and changing electronic structures of metal oxides [7]. The low-dimensional nanomaterial and porous structure were generally applied to practical gas-sensing, because the increased specific surface area always meant a larger resistance variation of sensing materials and more efficient reactions at the surface [11,12]. The synthetic strategy presented here could be generally extended to design other semiconductor metal oxide gas sensors with outstanding performances
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