Hierarchical aloe-like SnO 2 nanoflowers and their gas sensing properties
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ngyang Li Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602, USA
Xiaodan Wang, Yan Li, Quanshui Li, and Fengping Wanga) Department of Physics, School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, People’s Republic of China (Received 31 January 2018; accepted 27 March 2018)
Unique SnO2 monoflowers with an aloe-like morphology were successfully synthesized via a onestep hydrothermal method. The structural, chemical, and physical characteristics were investigated. The results exhibited that the as-prepared sample was assembled by triangle rutile SnO2 nanoslices with rough surfaces. A possible crystal growth and nanostructure assembling mechanism was proposed. The Raman peaks in 171, 235, and 211 cm 1 proved that a large amount of oxygen defects existed inside the sample, which might narrow the band gap from 3.6 eV of pure SnO2 to 2.7 eV of the sample. The sensor fabricated by aloe-like SnO2 nanostructures exhibited an excellent response and selectivity to ethanol. The developed sensor can detect ethanol as low as 10 ppm at 360 °C. The prepared aloe-like SnO2 microflower sensor exhibited a gas sensing response of about 7.46 when exposed to 100 ppm of ethanol gas at 360 °C, which was probably related to more numerous defects and thinner structure of aloe-like SnO2.
I. INTRODUCTION
Solid-state gas sensors, especially those which are based on metal oxide semiconductors, have been widely used in many applications such as environmental pollution removal, health care, defense, domestic security and safety, food industry, and medical.1–6 This is due to their low cost, ease of synthesis, simple crystal structure, small physical size, prominent stability, high sensitivity, and rapid response.7 Different types of metal oxide materials have been investigated for gas sensing applications, such as Nb2O5,8 ZnO,9–11 WO3,12,13 TiO2,14,15 In2O3,16,17 Fe2O3,18 and SnO2.19 Among these metal oxides, tin oxide is a very important n-type oxide semiconductor with a wide direct band gap (Eg 5 3.6 eV), high conductivity, tunable morphology and crystallinity, and chemical stability, which offers varied technological applications, such as lithium battery,20 optic-electronic device,21–23 dye-sensitized solar cell,24 catalyst,25 and gas sensor.26–28 Because of its excellent performance and practical application, various routes have been used to obtain SnO2 crystals and nanoarchitectures, including hydrothermal technique,29 sol–gel method,30 and chemical vapor deposition.22,31 Hydrothermal synthesis, which a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2018.94
required high temperature as well as pressure, has been most widely used, as the result of its convenient manipulation and flexibility in controlling the size and morphology of the resulting (nano)structures.32 One of the most important applications of the SnO2 material is gas sensors which have been proved to be excellent in gas sensing properties toward ethanol detection.1
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