Zn(OH)F Nanorods for Highly Sensitive NO 2 Gas Sensor Applications
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Zn(OH)F Nanorods for Highly Sensitive NO2 Gas Sensor Applications Tae-yil Eom SKKU Advanced Institute of Nano Technology, Sungkyunkwan University, Suwon 16419, Korea
Joon-Shik Park∗ Smart Sensor Research Center, Korea Electronics Technology Institute (KETI), Seongnam 13509, Korea
Hoo-Jeong Lee† Department of Smart Fab. Technology, Sungkyunkwan University, Suwon 16419, Korea (Received 12 October 2020; revised 19 October 2020; accepted 20 October 2020) In this study, Zn(OH)F nanorods were synthesized via a microwave-assisted hydrothermal process and employed for NO2 gas sensor, for the first time. Without adding NH4 F in the synthesis process, caltrop-like ZnO structure was formed. The characteristics of Zn(OH)F nanorods were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), and compared to those of caltrop-like ZnO. Additionally, the Zn(OH)F nanorods were further systematically studied by annealing them at 250, 350, and 450 ◦ C to examine thermal stability. The Zn(OH)F nanorods start to transform after annealing at 350 ◦ C. The sensor based on the Zn(OH)F nanorods showed very high response of 63.4 toward 1.3 ppm of NO2 gas at 100 ◦ C, which is 8.6 times higher than the response of the sensor based on the caltrop-like ZnO. In addition, the sensor based on Zn(OH)F nanorods showed an excellent selectivity toward H2 (5 ppm), C2 H5 OH (10.6 ppm), NH3 (10.6 ppm), C6 H5 CH3 (36.2 ppm), and CH3 COCH3 (2.8 ppm). Keywords: Zn(OH)F, NO2 gas sensor, Microwave-assisted, Highly sensitive, Annealing temperature variations DOI: 10.3938/jkps.77.1055
I. INTRODUCTION Nitrogen dioxide (NO2 ) generated from combustion of fossil fuels is a major atmospheric pollutant which causes respiratory diseases [1, 2]. Metal oxide semiconductors such as ZnO, SnO2 , and In2 O3 have been used as sensing materials of gas sensors for NO2 detection [3– 5]. Among them, ZnO, as a n-type material, is a good candidate for NO2 sensing material owing to its high response, low cost, non-toxicity, and diverse morphologies [3, 6]. For instance, in a study done by Agarwal et al., ZnO nanoflowers-based sensor was fabricated, showing a response of around 35 toward NO2 gas of 1 ppm [7]. Lee et al. also reported ZnO-rGO sensing membranes, exhibiting a response of 47.4% toward NO2 gas of 100 ppm [8]. Wang et al. synthesized ZnO nanorod/Au hybrids to enhance NO2 response (4.66 to 1 ppm) [9]. Recently, metal fluoride hydroxide materials such as Zn(OH)F, Co(OH)F, and Fe(OH)F, which are distinct from the conventional metal oxide materials, received ∗ E-mail: † E-mail:
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pISSN:0374-4884/eISSN:1976-8524
attentions as being applied to chemical catalysts, photocatalysts, and Li/Na-ion batteries for their high conductivity and good electrochemical property [10–12]. Considering reported high NO2 sensing performances of ZnO materials, Zn(OH)F, with a good catalytic property, could be a possible candidate for NO2 gas sensor. In this w
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