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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>
Wide Contact Structures for Low-Noise Nanochannel Devices Based on a Carbon Nanotube Network
Lee, Hyungwoo,Lee, Minbaek,Namgung, Seon,Hong, Seunghun American Chemical Society 2010 ACS NANO Vol.4 No.12
<P/><P>We have developed a wide contact structure for low-noise nanochannel devices based on a carbon nanotube (CNT) network. This low-noise CNT network-based device has a dumbbell-shaped channel, which has wide CNT/electrode contact regions and, in effect, reduces the contact noise. We also performed a systematic analysis of structured CNT networks and established an empirical formula that can explain the noise behavior of arbitrary-shaped CNT network-based devices including the effect of contact regions and CNT alignment. Interestingly, our analysis revealed that the noise amplitude of <I>aligned</I> CNT networks behaves quite differently compared with that of <I>randomly oriented</I> CNT networks. Our results should be an important guideline in designing low-noise nanoscale devices based on a CNT network for various applications such as a highly sensitive low-noise sensor.</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>
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..
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>