Elsevier

Applied Surface Science

Volume 476, 15 May 2019, Pages 391-401
Applied Surface Science

Full Length Article
ppb level triethylamine detection of yolk-shell SnO2/Au/Fe2O3 nanoboxes at low-temperature

https://doi.org/10.1016/j.apsusc.2019.01.110Get rights and content

Highlights

  • Novel SnO2/Au/Fe2O3 yolk-shell nanoboxes have been successfully synthesized.

  • The growth mechanism of SnO2/Au/Fe2O3 nanoboxes was investigated systematically.

  • Yolk-shell SnO2/Au/Fe2O3 nanoboxes exhibited high response to ppb level of TEA gas.

Abstract

Yolk-shell nanostructures with high specific surface area and more active areas become the development direction of gas sensors. In this work, yolk-shell SnO2/Au/Fe2O3 nanoboxes with specific surface area of 38.3 m2 g−1 were successfully prepared. The size of Fe2O3 nanocubes was about 300 nm, the thickness of SnO2 was about 20 nm and the diameter of Au nanoparticles was about 12 nm. Benefiting from the distinctive structure and catalytic activity of precious metals, the as-prepared SnO2/Au/Fe2O3 yolk-shell nanostructures showed outstanding response to triethylamine (TEA) gas at 240 °C. The response value to 100 ppm TEA gas was 126.84, which was about 6 times and 14 times of the Au/Fe2O3 and Fe2O3 samples. In addition, yolk-shell SnO2/Au/Fe2O3 nanoboxes also exhibited a low detection limit (50 ppb), good response and recovery character (7/10 s). This experiment provided novel ideas for the design of new nanostructures for gas sensors.

Introduction

Metal oxide semiconductors (MOSs) have been widely used in the field of gas sensors due to their miniaturized dimensions, availability of easy fabrication methods, low-costs, and considerable chemical, structural and environmental stabilities [1], [2], [3], [4]. Among the MOSs, iron oxides and their composites are promising candidates as less expensive and their remarkable properties in gas sensing, photocatalyst, magnetic, and so on [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15]. Particularly, recent attentions have been focused on gas sensing properties of hematite (α-Fe2O3) with different microstructures and morphologies due to its high selectivity towards volatile organic compounds (VOCs). For instance, Wang et al. successfully synthesized three-dimensional nanostructures of α-Fe2O3 materials via an environmentally friendly hydrothermal approach. They found that the well-defined bilayer interface effectively enhanced the ethanol sensing performance of the α-Fe2O3 nanostructures [16]. Zhang et al. reported hollow sea urchin-like α-Fe2O3 nanostructures exhibited significant improvements in ethanol sensing characteristics [17].

On the other hand, tin oxide (SnO2), as another important functional material, has been also intensively investigated due to its unique properties and great potential applications [18], [19], [20], [21], [22], [23], [24]. Recently, many reports demonstrated that composite system can improve the gas-sensing performance of metal oxide [25]. Notably, many studies have demonstrated that the gas sensing performance can be significantly improved by formation of SnO2/Fe2O3 composites. Yu et al. demonstrated the excellent acetone sensing performances of α-Fe2O3@SnO2 core-shell heterostructure nanotubes [26]. In our previous work, heterostructures composed of SnO2 nanorod/Fe2O3 nanocubes were prepared by hydrothermal route, which showed obviously improved gas sensing properties when compared to pure Fe2O3 nanocubes [27]. Different from the traditional bulk materials, the hollow structures generally lead to an efficiently increase in catalytic activity because of the larger specific area. Therefore, yolk-shell nanostructures with a good wealth of outstanding properties can exhibit more space for applications in gas sensors [16], [28]. Therefore, the design of SnO2/Fe2O3 composites with novel yolk-shell architectures is believed to be an effective method to construct high performance gas sensors.

In addition, the introduction of noble metal (such as Au, Ag, Pt) can also improve the gas sensing properties because noble metals could act as catalysts to modify the surface of metal oxide semiconductors [29], [30], [31]. However, to the best of our knowledge, the report on synthesis and gas sensing performances of iron oxide-noble metal-tin oxide ternary nanocomposites has been lacking. Herein, a new type of ternary hybrid architecture, yolk–shell SnO2/Au/Fe2O3 nanobox, has been designed and fabricated. The results revealed that the yolk–shell SnO2/Au/Fe2O3 nanoboxes exhibited significantly enhanced sensing performance to triethylamine (TEA) in terms of high response, low detection limit (50 ppb), better selectivity, and rapid response and recover, holding great potential as a high-performance sensing material for gas sensors.

Section snippets

Synthesis of Fe2O3 nanocubes

In a typical synthesis process, 2.16 g of FeCl3 and 3.244 g of NaOH were added into 10 mL of dissolved water respectively. Next, the two parts of solutions were mixed evenly. The mixture was poured into a flask, transferred into oven and aged at 100 °C for 90 h to obtain the Fe2O3 nanotubes. The precipitates were collected, washed and dried.

Synthesis of Au/Fe2O3 nanocubes

The Au/Fe2O3 nanocubes were synthesized by our previous method. 50 mg of as-prepared Fe2O3 samples was scattered into 15 mL deionized water and sonicated

Morphological and structural characterization

The XRD patterns in Fig. 1 display the crystal phase composition of the five samples. As can be seen in the obtained XRD patterns in panel 1(a), all diffraction peaks were attributed to the standard XRD patterns of Fe2O3 (JCPDS card no. 33-0664) and no impurity peaks were observed. The diffraction peaks of Au (JCPDS card No. 65-2870) can be seen in panel 1(b). The XRD patterns in panel 1(c) and 1(d) showed a steamed bread peak between 20 and 30°, which was presumably amorphous silicon oxide.

Conclusions

In summary, we have successfully synthesized the unique SnO2/Au/Fe2O3 ternary hybrid architectures. The as-synthesized nanocomposites present the typical yolk-shell nanobox structures with hollow interiors, which consisted of Fe2O3 nanocubes, loaded catalytic Au nanoparticles, and SnO2 shells. The sensor based on yolk-shell SnO2/Au/Fe2O3 nanoboxes delivers a higher response than most of the other reported TEA sensors, relatively rapid response and recover, and outstanding selectivity for TEA

Acknowledgements

This work was financially supported by National Natural Science Foundation of China (No. 61102006), and Natural Science Foundation of Shandong Province, China (No. ZR2018LE006 and ZR2015EM019).

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