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Flexible NO2 gas sensor using multilayer graphene films by chemical vapor deposition
HongKyw Choi,Hu Young Jeong,Dae-Sik Lee,Choon-Gi Choi,Sung-Yool Choi 한국탄소학회 2013 Carbon Letters Vol.14 No.3
We report a highly sensitive NO2 gas sensor based on multi-layer graphene (MLG) films synthesized by a chemical vapor deposition method on a microheater-embedded flexible substrate. The MLG could detect low-concentration NO2 even at sub-ppm (<200 ppb) levels. It also exhibited a high resistance change of ~6% when it was exposed to 1 ppm NO2 gas at room temperature for 1 min. The exceptionally high sensitivity could be attributed to the large number of NO2 molecule adsorption sites on the MLG due to its a large surface area and various defect-sites, and to the high mobility of carriers transferred between the MLG films and the adsorbed gas molecules. Although desorption of the NO2 molecules was slow, it could be enhanced by an additional annealing process using an embedded Au microheater. The outstanding mechanical flexibility of the graphene film ensures the stable sensing response of the device under extreme bending stress. Our large-scale and easily reproducible MLG films can provide a proof-of-concept for future flexible NO2 gas sensor devices.
최홍규(HongKyw Choi),송복득(Bok Deuk Song),김성훈(Sung-Hoon Kim) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.6
COVID-19로 인해 공연·영상·문화산업 부분에 다양한 형태로 영향을 미치고 있다. 비대면이 일상이 되고 온라인으로 다양한 콘텐츠를 즐기게 됨에 따라 소비자들은 실재감과 사실감이 배가된 콘텐츠를 요구하고 있다. 이와 같은 요구에 발맞춰 여러 방면에서 입체 영상 콘텐츠가 제작되고 해당 산업군에 관한 관심이 높아지고 있다. 본 논문은 s3D 공연장과 s3D 공연을 합성하여 소비자가 선택한 공연장에 시청하고자 하는 공연이 s3D로 나타낼 수 있는 입체미디어 플랫폼 개발을 위한 s3D 영상 합성 시스템에 관한 내용이다. s3D 영상 합성을 위해 선행되어야 하는 부분은 두 개 이상의 s3D 영상이 위화감 없이 구현되기 위해 입체 값을 일치시켜야 한다. 본 연구에서는 입체 값을 조절할 수 있는 여러가지 변수중에 IAD(Inter-Axial Distance)를 조절함으로써 s3D 배경영상에 s3D 영상이 위화감 없이 합성 가능한 시스템을 개발하고자 한다.
Lee, Hyosun,Nedrygailov, Ievgen I.,Lee, Young Keun,Lee, Changhwan,Choi, Hongkyw,Choi, Jin Sik,Choi, Choon-Gi,Park, Jeong Young American Chemical Society 2016 NANO LETTERS Vol.16 No.3
<P>Direct detection of hot electrons generated by exothermic surface reactions on nanocatalysts is an effective strategy to obtain insight into electronic excitation during chemical reactions. For this purpose, we fabricated a novel catalytic nanodiode based on a Schottky junction between a single layer of graphene and an n-type TiO2 layer that enables the detection of hot electron flows produced by hydrogen oxidation on Pt nanoparticles. By making a comparative analysis of data obtained from measuring the hot electron current (chemicurrent) and turnover frequency, we demonstrate that graphene's unique electronic structure and extraordinary material properties, including its atomically thin nature and ballistic electron transport, allow improved conductivity at the interface between the catalytic Pt nanoparticles and the support. Thereby, graphene-based nanodiodes offer an effective and facile way to approach the study of chemical energy conversion mechanisms in composite catalysts with carbon-based supports.</P>
Aligned Circular-Type Nanowire Transistors Grown on Multilayer Graphene Film
Kim, Hwansoo,Choi, Hongkyw,Choi, Sung-Yool,Ju, Sanghyun American Chemical Society 2011 The Journal of Physical Chemistry Part C Vol.115 No.45
<P>High-performance transistors using semiconducting nanowires are very promising devices for flexible or transparent electronic applications. However, nanowire-based transistors inevitably have placement and alignment issues, which make them troublesome for real-world applications and can be limiting factors in novel applications. Here we present a novel device structure that can be easily adapted for producing high-yield nanowire transistors. We fabricated fully transparent circular tin oxide (SnO<SUB>2</SUB>) nanowire transistors employing multilayer graphene films (MGFs) as a seed electrode and aligned nanowires as a semiconductor channel. The nanowires were grown directly on MGFs without metal catalysts through a vapor–solid (VS) mechanism. On the basis of these properties, aligned SnO<SUB>2</SUB> nanowires were grown only on the exposed MGF using patterned MGF/SiO<SUB>2</SUB> structures. Regardless of the growth direction of the nanowires centered on the MGF, the as-grown nanowires can play the role of transistor channels because of the circular shape of the gate and the source-drain electrodes. Consequently, the yield rate of circular nanowire transistor structure was around two times as high as that of existing linear nanowire transistor structure.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2011/jpccck.2011.115.issue-45/jp2052008/production/images/medium/jp-2011-052008_0005.gif'></P>
Hybrid nanowire–multilayer graphene film light-emitting sources
Kim, Sangdan,Choi, Hongkyw,Jung, Mi,Choi, Sung-Yool,Ju, Sanghyun IOP Pub 2010 Nanotechnology Vol.21 No.42
<P>We report a versatile hybrid device consisting of one-dimensional ZnS and Te-doped ZnS (ZnS:Te) nanowires (NWs) upon two-dimensional multilayer graphene films (MGFs). Single-crystalline ZnS and ZnS:Te NWs were grown directly on a MGF without a catalyst, and exhibited blue-green and blue emission peaks of ∼ 503 and ∼ 440 nm. A field emission light emitter using ZnS:Te NWs on a MGF was demonstrated, and it indicates excellent contact properties between the NWs and MGFs. The resulting hybrid devices are promising candidates for potential applications as building blocks for the development of highly functional and efficient electroluminescent devices and field-emitting devices including flexible and/or transparent display devices. </P>