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Hyunsung Ko,김봉규,Kyung Hyun Kim,허철,Wan-Joong Kim,Jongcheol Hong,Seon Hee Park,Seong-Seok Yang,Ho-Jin Jang,성건용 한국광학회 2010 Current Optics and Photonics Vol.14 No.4
This study reports a portable and precision photonic biosensor reader that can measure the concentration of a particular antigen using an optical resonant reflection biosensor (ORRB). To create a compact biosensor reader, a compact tunable vertical-cavity surface-emitting laser (VCSEL) and a compact built-in wavelength meter were manufactured. The wavelength stability and accuracy of the compact built-in wavelength meter were measured to be less than 0.02 nm and 0.06 nm, respectively. The tunable VCSEL emission wavelength was measured with the compact built-in wavelength meter, it has a fast sweep time (~ 10 seconds) and a wide tuning range (> 4 nm) that are sufficient for biosensor applications based on ORRB. The reflection spectrum of a plastic based ORRB chip was measured by the fabricated portable photonic biosensor reader using the VCSEL and wavelength meter. Although the reader is the size of a palmtop device, it could make a precise measurement of the peak wavelength on equal terms with a conventional bulky optical spectrometer.
Enhanced ethanol sensing properties of TeO2/In2O3 core-shell nanorod sensors
Hyunsung Ko,박성훈,Soyeon An,이종무 한국물리학회 2013 Current Applied Physics Vol.13 No.5
TeO2/In2O3 coreeshell nanorods were fabricated using thermal evaporation and sputtering methods. The multiple networked TeO2/In2O3 coreeshell nanorod sensor showed responses of 227-632%, response times of 50-160 s, and recovery times of 190-220 s at ethanol (C2H5OH) concentrations of 50-250 ppm at 300 ℃. The response values are 1.6-2.9 times higher and the response and recovery times are also considerably shorter than those of the pristine TeO2 nanorod sensor over the same C2H5OH concentration range. The origin of the enhanced ethanol sensing properties of the coreeshell nanorod sensor is discussed.
Enhanced NO2 Gas Sensing Properties of WO3-Coated Multiwall Carbon Nanotube Sensors.
Ko, Hyunsung,Park, Sunghoon,Park, Suyoung,Lee, Chongmu American Scientific Publishers 2015 Journal of Nanoscience and Nanotechnology Vol.15 No.7
<P>WO3-coated multiwall carbon nanotubes (MWCNTs) were fabricated by sputter-deposition of WO3 on MWCNT paste. The outer diameters of WO3-coated MWCNTs ranged from 20 to 40 nm and the lengths ranged up to a few tens of micrometers. The low-magnification TEM image of a typical WO3-coated CNT showed a CNT with an inner diameter of ~20 nm and a tube wall thickness of ~7 nm and WO3 shells with a thickness up to 10 nm at both edges of the tube. The WO3 shells were very nonuniform in thickness not only along the axis of the nanotube but also from one nanotube to the other. The sensing properties of multiple networked WO3-coated CNT sensors toward NO2 gas were examined. The WO3-coated MWCNT sensors showed responses of 120-221% over an NO2 concentration range of 1 to 5 ppm at room temperature. The responses were 1-2 fold higher than those of the pristine MWCNT sensor over the same NO2 concentration range. The origin of the enhancement of the MWCNTs in the response to NO2 by coating them with WO3 is discussed.</P>
Ko, Eun-Byul,Choi, Jae-Seok,Jung, Hyunsung,Choi, Sung-Churl,Kim, Chang-Yeoul American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.2
<P>Transparent conducting oxide (TCO) is widely used for the application of flat panel display like liquid crystal displays and plasma display panel. It is also applied in the field of touch panel, solar cell electrode, low-emissivity glass, defrost window, and anti-static material. Fluorine-doped tin oxide (FTO) thin films were fabricated by spray pyrolysis of ethanol -added FTO precursor solutions. FTO thin film by spray pyrolysis is very much investigated and normally formed at high temperature, about 500 degrees C. However, these days, flexible electronics draw many attentions in the field of IT industry and the research for flexible transparent conducting thin film is also required. In the industrial field, indium-tin oxide (ITO) film on polymer substrate is widely used for touch panel and displays. In this study, we investigated the possibility of FTO thin film formation at relatively low temperature of 250 degrees C. We found out that the control of volume of input precursor and exhaust gases could make it possible to form FTO thin film with a relatively low electrical resistance, less than 100 Ohm/sq and high optical transmittance about 88%.</P>
UV-assisted Room temperature Gas Sensing of GaN-core/ZnO-shell Nanowires
박성훈,Hyunsung Ko,김수현,이종무 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.10
GaN is highly sensitive to low concentrations of H2 in ambient air and is almost insensitiveto most other common gases. However, enhancing the sensing performance and the detectionlimit of GaN is a challenge. This study examined the H2-gas-sensing properties of GaN nanowiresencapsulated with ZnO. GaN-core/ZnO-shell nanowires were fabricated by using a two-step processcomprising the thermal evaporation of GaN powders and the atomic layer deposition of ZnO. Thecore-shell nanowires ranged from 80 to 120 nm in diameter and from a few tens to a few hundreds ofmicrometers in length, with a mean shell layer thickness of 8 nm. Multiple-networked pristine GaNnanowire and ZnO-encapsulated GaN (or GaN-core/ZnO-shell) nanowire sensors showed responsesof 120 − 147% and 179 − 389%, respectively, to 500 − 2,500 ppm of H2 at room temperatureunder UV (254 nm) illumination. The underlying mechanism of the enhanced response of the GaNnanowire to H2 gas when using ZnO encapsulation and UV irradiation is discussed.
Photoluminescence in MgO-ZnO Nanorods Enhanced by Hydrogen Plasma Treatment
박성훈,Hyunsung Ko,문영호,이종무 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.11
MgO nanorods were fabricated by the thermal evaporation of Mg3N2. The influence of ZnO sheathing and hydrogen plasma exposure on the photoluminescence (PL) of the MgO nanorods was studied. PL measurements of the ZnO-sheathed MgO nanorods showed two main emission bands: the near band edge emission band centered at ~380 nm and the deep level emission band centered at ~590 nm both of which are characteristic of ZnO. The near band edge emission from the ZnO-sheathed MgO nanorods was enhanced with increasing the ZnO shell layer thickness. The near band edge emission from the ZnO-sheathed MgO nanorods appeared to be enhanced further by hydrogen plasma irradiation. The underlying mechanisms for the enhancement of the NBE emission from the MgO nanorods by ZnO sheathing and hydrogen plasma exposure are discussed.