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Real-time detection of chlorine gas using Ni/Si shell/core nanowires
Lee, Dong-Jin,Heo, Kwang,Lee, Hyungwoo,Jin, Joon-Hyung,Chang, Hochan,Park, Minjun,Lee, Han-Bo-Ram,Kim, Hyungjun,Lee, Byung Yang Springer US 2015 NANOSCALE RESEARCH LETTERS Vol.10 No.1
<P>We demonstrate the selective adsorption of Ni/Si shell/core nanowires (Ni-Si NWs) with a Ni outer shell and a Si inner core on molecularly patterned substrates and their application to sensors for the detection of chlorine gas, a toxic halogen gas. The molecularly patterned substrates consisted of polar SiO<SUB>2</SUB> regions and nonpolar regions of self-assembled monolayers of octadecyltrichlorosilane (OTS). The NWs showed selective adsorption on the polar SiO<SUB>2</SUB> regions, avoiding assembly on the nonpolar OTS regions. Utilizing these assembled Ni-Si NWs, we demonstrate a sensor for the detection of chlorine gas. The utilization of Ni-Si NWs resulted in a much larger sensor response of approximately 23% to 5 ppm of chlorine gas compared to bare Ni NWs, due to the increased surface-to-volume ratio of the Ni-Si shell/core structure. We expect that our sensor will be utilized in the future for the real-time detection of halogen gases including chlorine with high sensitivity and fast response.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1186/s11671-015-0729-2) contains supplementary material, which is available to authorized users.</P>
Lee, Minbaek,Lee, Joohyung,Kim, Tae Hyun,Lee, Hyungwoo,Lee, Byung Yang,Park, June,Jhon, Young Min,Seong, Maeng-Je,Hong, Seunghun IOP Pub 2010 Nanotechnology Vol.21 No.5
<P>Nanoscale sensors based on single-walled carbon nanotube (SWNT) networks have been considered impractical due to several fundamental limitations such as a poor sensitivity and small signal-to-noise ratio. Herein, we present a strategy to overcome these fundamental problems and build highly-sensitive low-noise nanoscale sensors simply by controlling the structure of the SWNT networks. In this strategy, we prepared nanoscale width channels based on aligned SWNT networks using a directed assembly strategy. Significantly, the aligned network-based sensors with narrower channels exhibited even better signal-to-noise ratio than those with wider channels, which is opposite to conventional random network-based sensors. As a proof of concept, we demonstrated 100 nm scale low-noise sensors to detect mercury ions with the detection limit of ∼1 pM, which is superior to any state-of-the-art portable detection system and is below the allowable limit of mercury ions in drinking water set by most government environmental protection agencies. This is the first demonstration of 100 nm scale low-noise sensors based on SWNT networks. Considering the increased interests in high-density sensor arrays for healthcare and environmental protection, our strategy should have a significant impact on various industrial applications. </P>
Hyungwoo Kim,Jangwon Lee,Jongsuh Lee,Jaeyub Hyun,Semyung Wang IEEE 2016 IEEE transactions on magnetics Vol.52 No.3
<P>In this paper, a magnetic resonator for wireless energy transfer system is designed using topology optimization based on an electromagnetic wave analysis. To analyze the magnetic resonator, the finite-difference time-domain method in a 2-D transverse magnetic mode is used with a Gaussian pulse source and perfectly matched layers. The topology optimization using solid isotropic material with the penalization method of a magnetic resonator is conducted to maximize magnetic energy. After these approaches, the fast Fourier transform is used to obtain the response of the magnetic resonator system over a wide range of frequencies.</P>
Comparative analysis of human facial skin microbiome between topical sites compared to entire face
Lee Haeun,Jeong Jinuk,Oh Yunseok,Lee Cherl-Jun,Mun Seyoung,Lee Dong-Geol,Jo HyungWoo,Heo Young Mok,Baek Chaeyun,Heo Chan Yeong,Kang So Min,한규동 한국유전학회 2021 Genes & Genomics Vol.43 No.12
Background Skin is an essential outer barrier and supports the growth of commensal microorganisms that protects a host from the ofense of foreign toxic organisms. With the rapid development of next-generation sequencing (NGS)-based applications, skin microbiome research for facial health care has reached industry growth, such as therapy and cosmetic product development. Despite the acceleration of skin microbiome research, experimental standardization protocol has not yet been established in the facial site and method of sampling. Objective Thus, we aimed to investigate the diferences in microbial composition at each facial site (cheek, mouth, forehead, and entire face) using comprehensive microbiome analysis. Methods Twelve specimens from three men (four specimens per one person) were collected. The hypervariable regions (V3–V4) of the bacterial 16S rRNA gene were targeted for 16S amplicon library construction and classifcation of bacterial taxonomy. Skin microbial composition for all specimens was investigated, and the diferences site-by-site in skin microbial composition were analyzed and evaluated by the various statistical tests. Results We were able to validate the independent correlation between the skin microbiome composition and the facial sites. The cheek site showed the highest alpha-diversity in richness and evenness scores compared to the forehead and mouth. The cheek and mouth sites showed a positive correlation (R2 value>0.93) with the entire face, while the forehead sites were negatively correlated (R2 value<0.2). Given the relative abundance based on statistical correlation analysis, we estimated that the cheek site could be considered an optimal topical site to replace the entire face. Conclusion Our study suggests that skin microbiome profling of four facial sites confrms that the cheek shows the most similar skin fora with the entire face. This study would be informative for preventing bias caused by sampling methods before researching and understanding skin cosmetics development or skin diseases.
Graphene–nanowire hybrid structures for high-performance photoconductive devices
Lee, Hyungwoo,Heo, Kwang,Park, Jaesung,Park, Yongju,Noh, Seunguk,Kim, Kwang S.,Lee, Changhee,Hong, Byung Hee,Jian, Jikang,Hong, Seunghun The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.17
<P>Graphene–CdS nanowire (NW) hybrid structures with high-speed photoconductivity were developed. The hybrid structure was comprised of CdS NWs which were selectively grown in specific regions on a single-layer graphene sheet. The photoconductive channels based on graphene–CdS NW hybrid structures exhibited much larger photocurrents than graphene-based channels and much faster recovery speed than CdS NW network-based ones. Our graphene–CdS NW structures can be useful because they were much faster than commercial CdS film-based photodetectors and had photocurrents large enough for practical applications.</P> <P>Graphic Abstract</P><P>We have developed a photoconductive channel based on graphene–CdS nanowire hybrid structures which exhibited large photocurrent and fast recovery speed. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm16565a'> </P>
Nanoscale Direct Mapping of Noise Source Activities on Graphene Domains
Lee, Hyungwoo,Cho, Duckhyung,Shekhar, Shashank,Kim, Jeongsu,Park, Jaesung,Hong, Byung Hee,Hong, Seunghun American Chemical Society 2016 ACS NANO Vol.10 No.11
<P>An electrical noise is one of the key parameters determining the performance of modern electronic devices. However, it has been extremely difficult, if not impossible, to image localized noise sources or their activities in such devices. We report a 'noise spectral imaging' strategy to map the activities of localized noise sources in graphene domains. Using this method, we could quantitatively estimate sheet resistances and noise source densities inside graphene domains, on domain boundaries and on the edge of graphene. The results show high activities of noise sources and large sheet resistance values at the domain boundary and edge of graphene. Additionally, we showed that the top layer in double layer graphene had lower noises than single-layer graphene. This work provides valuable insights about the electrical noises of graphene. Furthermore, the capability to directly map noise sources in electronic channels can be a major breakthrough in electrical noise research in general.</P>
LEE, HEE JUNG,JO, SUZY,RYU, JEONGHYUN,JEONG, HAN-SOL,LEE, GUEMSAN,RYU, MI HEON,JUNG, MYEONG HO,KIM, HYUNGWOO,KIM, BYUNG JOO SPANDIDOS PUBLICATIONS 2015 MOLECULAR MEDICINE REPORTS Vol.12 No.2
<P>Schisandra chinensis Turcz. fruit is widely used to treat skin diseases. The aim of this study was to determine the anti-inflammatory effects of the methanol extract of S. chinensis (MESC) on 1-fluoro-2,4-dinitrofluorobenzene (DNFB)-induced contact dermatitis (CD) in mice. The effects of MESC on ear thickness and weight, histopathological changes, immune cell filtration and cytokine production were investigated in DNFB-induced CD mice. Topical application of MESC effectively inhibited ear swelling (30 or 300 μg on the left ear, P<0.001; 30 μg on the right ear, P<0.001). MESC also inhibited hyperplasia, spongiosis (100 μg/ear, P<0.05 and 300 μg/ear, P<0.001, respectively) and immune cell infiltration (100 μg/ear, P<0.05; 300 μg/ear, P<0.001) induced by DNFB. In addition, MESC suppressed increases in tumor necrosis factor (TNF)-α levels (100 or 300 μg/ear, P<0.05), interferon (INF)-γ (30 μg/ear, P<0.05; 100 μg/ear, P<0.01; 300 μg/ear, P<0.001), interleukin (IL)-6 (300 μg/ear, P<0.05) and monocyte chemoattractant protein (MCP)-1 (30 μg/ear, P<0.05; 100 μg/ear, P<0.01; 300 μg/ear, P<0.001). These results suggest that the anti-inflammatory effects of MESC are mediated by the reduced production of TNF-α, IFN-γ, IL-6 and MCP-1, and that MESC has potential use for the treatment of inflammatory skin diseases.</P>
Unified low power optimization algorithm by gate freezing, gate sizing and buffer insertion
Hyungwoo Lee,Hakgun Shin,Juho Kim 한국물리학회 2005 Current Applied Physics Vol.5 No.4
One of the major factors contributing to the power dissipation in CMOS digital circuits is the switching activity. Many of suchswitching activities include spurious pulses, called glitches. In this paper, we propose a new method of glitch reduction by gatefreezing, gate sizing, and buer insertion. The proposed method unies gate freezing, gate sizing, and buer insertion into a singleoptimization process to maximize the glitch reduction. The eectiveness of our method is veried experimentally using LGSynth91benchmark circuits with a 0.5l m standard cell library. Our optimization method reduces glitches by 65.64% and the power by31.03% on average..