title: Ultrasensitive NO2 Sensor Based on Ohmic Metal-Semiconductor Interfaces of Electrolytically Exfoliated Graphene/Flame-Spray-Made SnO2 Nanoparticles Composite Operating at Low Temperatures.
abstract: In this work, flame-spray-made undoped SnO2 nanoparticles were loaded with 0.1-5 wt % electrolytically exfoliated graphene and systematically studied for NO2 sensing at low working temperatures. Characterizations by X-ray diffraction, transmission/scanning electron microscopy, and Raman and X-ray photoelectron spectroscopy indicated that high-quality multilayer graphene sheets with low oxygen content were widely distributed within spheriodal nanoparticles having polycrystalline tetragonal SnO2 phase. The 10-20 μm thick sensing films fabricated by spin coating on Au/Al2O3 substrates were tested toward NO2 at operating temperatures ranging from 25 to 350 °C in dry air. Gas-sensing results showed that the optimal graphene loading level of 0.5 wt % provided an ultrahigh response of 26,342 toward 5 ppm of NO2 with a short response time of 13 s and good recovery stabilization at a low optimal operating temperature of 150 °C. In addition, the optimal sensor also displayed high sensor response and relatively short response time of 171 and 7 min toward 5 ppm of NO2 at room temperature (25 °C). Furthermore, the sensors displayed very high NO2 selectivity against H2S, NH3, C2H5OH, H2, and H2O. Detailed mechanisms for the drastic NO2 response enhancement by graphene were proposed on the basis of the formation of graphene-undoped SnO2 ohmic metal-semiconductor junctions and accessible interfaces of graphene-SnO2 nanoparticles. Therefore, the electrolytically exfoliated graphene-loaded FSP-made SnO2 sensor is a highly promising candidate for fast, sensitive, and selective detection of NO2 at low operating temperatures.
authors.affiliation: Department of Physics and Materials Science, Faculty of Science, Chiang Mai University , Chiang Mai 50202, Thailand.
authors.forename: Nantikan
authors.initials: N
authors.lastname: Tammanoon
authors.affiliation: Nanoelectronics and MEMS Laboratory, National Electronics and Computer Technology Center, National Science and Technology Development Agency , Klong Luang, Pathumthani 12120, Thailand.
authors.forename: Anurat
authors.initials: A
authors.lastname: Wisitsoraat
authors.affiliation: Nanoelectronics and MEMS Laboratory, National Electronics and Computer Technology Center, National Science and Technology Development Agency , Klong Luang, Pathumthani 12120, Thailand.
authors.forename: Chakrit
authors.initials: C
authors.lastname: Sriprachuabwong
authors.affiliation: Nanoelectronics and MEMS Laboratory, National Electronics and Computer Technology Center, National Science and Technology Development Agency , Klong Luang, Pathumthani 12120, Thailand.
authors.forename: Ditsayut
authors.initials: D
authors.lastname: Phokharatkul
authors.affiliation: Nanoelectronics and MEMS Laboratory, National Electronics and Computer Technology Center, National Science and Technology Development Agency , Klong Luang, Pathumthani 12120, Thailand.
authors.forename: Adisorn
authors.initials: A
authors.lastname: Tuantranont
authors.affiliation: Materials Science Research Center, Faculty of Science, Chiang Mai University , Chiang Mai 50202, Thailand.
authors.forename: Sukon
authors.initials: S
authors.lastname: Phanichphant
authors.affiliation: Department of Physics and Materials Science, Faculty of Science, Chiang Mai University , Chiang Mai 50202, Thailand.|Materials Science Research Center, Faculty of Science, Chiang Mai University , Chiang Mai 50202, Thailand.
authors.forename: Chaikarn
authors.initials: C
authors.lastname: Liewhiran
keywords: NO2 sensing; SnO2; flame spray pyrolysis; graphene; sensor