90 results on '"Chil Seong Ah"'
Search Results
2. Electrochromic devices based on ultraviolet-cured poly(methyl methacrylate) gel electrolytes and their utilisation in smart window applications
- Author
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Hyunjoo Lee, Yongseok Jun, Chanyong Lee, Juhee Song, Chil Seong Ah, and Yong Ju Yun
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Materials science ,business.industry ,General Chemistry ,Electrolyte ,Atmospheric temperature range ,medicine.disease_cause ,Electrochromic devices ,Poly(methyl methacrylate) ,chemistry.chemical_compound ,chemistry ,Electrochromism ,visual_art ,Materials Chemistry ,visual_art.visual_art_medium ,medicine ,Optoelectronics ,Methyl methacrylate ,business ,Ultraviolet ,Leakage (electronics) - Abstract
Electrochromic devices (ECDs) have been widely investigated for application in next-generation displays and smart windows thanks to their highly efficient optical transmittance modulation properties. However, several challenges such as chemical and environmental instabilities and leakage of electrolytes limit their practical applications. In this paper, we report a simple and efficient approach for synthesising ultraviolet (UV)-cured poly(methyl methacrylate) (PMMA) gels that can be used as safe electrolytes. The ECDs fabricated with the 10 min UV-cured PMMA gel electrolyte deliver remarkable device performances with a wide optical transmittance transition (ΔT) of 51.3% at a wavelength of 550 nm under −1.2–0 V bias range and fast switching times (Δt) of 1.5 s and 2.0 s for bleaching and colouration, respectively. In addition, excellent operational stability of 98.9% after 11 500 cycles and environmental stability at a wide temperature range of −20 to +70 °C are exhibited. Moreover, a smart electrochromic window system, including an ECD connected with an Arduino circuit, is developed. These smart windows can change colour by simultaneously monitoring the illumination and UV intensities of sunlight.
- Published
- 2020
3. Fabrication of Highly Transparent Electrochromic Mirror Device with Nanoporous Counter Electrode
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Yong-Hae Kim, Sujung Kim, Chil Seong Ah, Chi-Sun Hwang, Hojun Ryu, Joo Yeon Kim, Tae-Youb Kim, Juhee Song, Seong M. Cho, and Sang-Hoon Cheon
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Auxiliary electrode ,Fabrication ,Materials science ,business.industry ,Nanoporous ,Response time ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Reflectivity ,0104 chemical sciences ,Electrochromism ,Optoelectronics ,0210 nano-technology ,business - Published
- 2018
4. New switchable mirror device with a counter electrode based on reversible electrodeposition
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Juhee Song, Tae-Youb Kim, Sujung Kim, Joo Yeon Kim, Sang Hoon Cheon, Chil Seong Ah, Hojun Ryu, Seong M. Cho, Chi-Sun Hwang, Yong-Hae Kim, and Jeong-Ik Lee
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Auxiliary electrode ,Working electrode ,Materials science ,Bistability ,Renewable Energy, Sustainability and the Environment ,business.industry ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Ion ,Electrochromism ,Optoelectronics ,Deposition (phase transition) ,0210 nano-technology ,business ,Voltage - Abstract
A new structure for a switchable mirror device based on reversible electrodeposition is proposed. This device does not contain Cu ions in the electrolyte and adapts a counter electrode. The feasibility of the device was evaluated with a WO3 film, which is a well-known electrochromic material, as a counter electrode. Even in the absence of Cu ions, the WO3 film facilitates a clean erase feature in the device. Furthermore, using a pre-deposited Ag film as a working electrode, Ag deposition can be driven at a substantially lower voltage than that in conventional devices. Moreover the deposition current decreases with the progress of Ag deposition, and stops after completion of the deposition process. The results clearly indicate that the tri-bromine ion, which makes the self-erasing circulation, is not generated during Ag deposition process. The new switchable mirror shows excellent bistability and size scale-up is possible because it does not consume continuous current in the mirror state. By appling the proposed technology, a switchable mirror device with a 7 cm × 9 cm active area was successfully fabricated.
- Published
- 2018
5. Electrochromic device with self-diffusing function for light adaptable displays
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Seong M. Cho, Sang Hoon Cheon, Chi-Sun Hwang, Yong-Hae Kim, Chil Seong Ah, Hojun Ryu, Tae-Youb Kim, Joo Yeon Kim, and Juhee Song
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Nanostructure ,Materials science ,Renewable Energy, Sustainability and the Environment ,business.industry ,Scattering ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Viewing angle ,Electrochromic devices ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Optics ,Gamut ,Electrochromism ,Transmittance ,Optoelectronics ,Contrast ratio ,0210 nano-technology ,business - Abstract
Light-adaptable (LA) displays combining the advantages of reflective and emissive displays, are considered as the future of display technology. Electrochromic devices are potentially strong candidates for reflective-mode LA displays because of their high transmittance in the transparent state and low power consumption. However, the narrow viewing angle of these displays in relation to a hybrid structure of the LA display, is a technical barrier that must be overcome for the successful application of electrochromic devices to light-adaptable displays. In the present study, an electrochromic device with a self-diffusing function was developed for application to light-adaptable displays. Si3N4 scattering particles were incorporated in the TiO2 nanostructure-based electrochromic device. Efficient forward diffuse scatterings were obtained without deteriorating the total transmittance of the device. The contrast ratio and color gamut of the electrochromic device were dramatically improved because of the addition of the scattering particles.
- Published
- 2018
6. Photofragmentation dynamics of n-dodecanethiol-derivatized silver nanoparticles in cyclohexane
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Chil Seong Ah, Hyouk Soo Han, Kwan Kim, and Du-Jeon Jang
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Cyclohexane -- Chemical properties ,Excited state chemistry -- Analysis ,Photochemistry -- Analysis ,Chemicals, plastics and rubber industries - Abstract
Photochemical reaction of n-dodecanethiol-derivatized silver nanoparticles in cyclohexane is studied in the picosecond-second time range and is found to depend nonlinearly on the irradiance of photolysis light. The static absorption bleach by excitation at 532 and 355 nm increases with the irradiance raised to the powers of 1.9 and 1.4, respectively.
- Published
- 2000
7. Solution-processed Au–Ag core–shell nanoparticle-decorated yarns for human motion monitoring
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Yong Ju Yun, Yongseok Jun, Chil Seong Ah, Hyung Ju Park, and Wan Joong Kim
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Materials science ,General Chemical Engineering ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Nanoparticle ,Wearable computer ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Wearable systems ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Human motion ,01 natural sciences ,0104 chemical sciences ,Solution processed ,Core shell ,0210 nano-technology ,ComputingMethodologies_COMPUTERGRAPHICS - Abstract
Wearable strain sensors based on Au–Ag core–shell nanoparticle decorated yarns were fabricated by a solution-based approach. Smart wearable systems with our strain sensors that can monitor various human motions, including finger motion, marching and squatting, and transmit the information of human motion in real time to an LED light was demonstrated.
- Published
- 2017
8. Reflective Colored Organic Light-Emitting Diodes for Light-Adaptable Display
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Chil Seong Ah, Jonghee Lee, Joon Tae Ahn, Jeong-Ik Lee, Jaehyun Moon, Seong Chu Lim, Jong Tae Lim, and Seong M. Cho
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Materials science ,business.industry ,Biomedical Engineering ,Bioengineering ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Colored ,OLED ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business - Published
- 2016
9. Long-lived electrochromic device with multilevel bistability based on portable film-type polymer electrolytes
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Cheon Sang Hoon, Chihun Sung, Seong-Mok Cho, Cho Doo-Hee, Tae-Youb Kim, Ryu Hojun, Chil Seong Ah, Jisu Han, and Song Juhee
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chemistry.chemical_classification ,Materials science ,Bistability ,Renewable Energy, Sustainability and the Environment ,Polymer electrolytes ,business.industry ,02 engineering and technology ,Polymer ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochromic devices ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,Electrochromism ,Transmittance ,Optoelectronics ,Operating voltage ,0210 nano-technology ,business - Abstract
Long-lived electrochromic devices (ECDs) with multilevel bistability based on a portable film-type polymer electrolyte (PFPE) were fabricated and their optical and electrical properties were characterized. WO3 and NiOx, deposited via a vacuum method, were used as electrochromic materials, and PFPEs were assembled in ECDs by a transfer method. The PFPEs were fabricated by inserting a polyvinyl acetal (PVA) based gel electrolyte between a light and a tight release films. The PFPE-based ECD operated reliably for at least 109,000 cycles and showed excellent bistability in multilevel open circuits. For 30 min after removing the applied operating voltage, the ECD maintained 90% and 99% of the original coloration and decoloration transmittance at 550 nm, respectively. The average coloration and decoloration consumed charge and efficiency over 109,000 operation cycles were 4.2 and −4.5 mC/cm2 and 81.4 and −74.8 cm2/C, respectively.
- Published
- 2021
10. Optical and Electrical Properties of Electrochromic Devices Depending on Electrolyte Concentrations and Cell Gaps
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Yong-Hae Kim, Joo Yeon Kim, Sang-Hoon Cheon, Tae-Youb Kim, Juhee Song, Seong M. Cho, Hojun Ryu, Chi-Sun Hwang, and Chil Seong Ah
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Materials science ,genetic structures ,Bistability ,business.industry ,Response time ,Viologen ,02 engineering and technology ,General Chemistry ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochromic devices ,01 natural sciences ,0104 chemical sciences ,Electrochromism ,Electrode ,Transmittance ,medicine ,Optoelectronics ,0210 nano-technology ,business ,medicine.drug - Abstract
The optical and electrical properties of electrochromic devices (ECDs) have been studied as a function of the electrolyte concentration and the cell gap. During tests, the electrolyte concentration was adjusted from 0.01 to 1 M LiClO4, and the cell gaps between the positive and negative electrodes were set at 25, 60, and 100 µm. By varying the electrolyte concentrations and the cell gap, various parameters such as the transmittance, response time, charge consumption, coloration efficiency, and bistability of ECD were comparatively analyzed. Viologen (VO) was used as the reduction electrochromic material, and triarylamine (TAA) was used as the oxidation material.
- Published
- 2016
11. Electrochromic mirror using viologen-anchored nanoparticles
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Tae-Youb Kim, Han Na Kim, Hojun Ryu, Juhee Song, Seong M. Cho, Yong-Hae Kim, and Chil Seong Ah
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Materials science ,Nanoparticle ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,chemistry.chemical_compound ,Optics ,medicine ,General Materials Science ,Sol-gel ,Magnesium fluoride ,Dynamic range ,business.industry ,Mechanical Engineering ,Viologen ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,chemistry ,Mechanics of Materials ,Electrochromism ,Optoelectronics ,Contrast ratio ,0210 nano-technology ,business ,Layer (electronics) ,medicine.drug - Abstract
Electrochromic mirrors (ECMs) that are used in automobile mirrors need to have high reflectance, a high contrast ratio, and a clear image. In particular, it is critical that distortions of clear images are minimized for safety. Therefore, an ECM is fabricated using viologen-anchored nanoparticles and a magnesium fluoride (MgF2) layer with an anti-reflection function. The ECM has approximately 30.42% in the reflectance dynamic range and 125 cm2/C high coloration efficiency.
- Published
- 2016
12. Driving mechanism of high speed electrochromic devices by using patterned array
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Joo Yeon Kim, Tae-Youb Kim, Chil Seong Ah, Seong M. Cho, and Hojun Ryu
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Materials science ,Renewable Energy, Sustainability and the Environment ,Nanoparticle ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochromic devices ,01 natural sciences ,Durability ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Switching time ,Mechanism (engineering) ,0210 nano-technology - Abstract
Electrochromic devices (ECDs) having a high switching speed and a good durability were developed with viologen-anchored TiO 2 (VTO) nanoparticles and antimony-doped SnO 2 (ATO) nanoparticles. The fabricated ECDs showed a good stability after 30,000 cycles driving at 4 Hz speed. Also, the dynamic behavior of their devices was studied using 6×6 patterned array cells. The driving tests of 4 types were used to understand the exact driving mechanism and to prevent the rapid blur problem.
- Published
- 2016
13. Reflective‐Type Transparent/Colored Mirror Switchable Device Using Reversible Electrodeposition with Fabry–Perot Interferometer
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Juhee Song, Seong M. Cho, Jisu Han, Tae-Youb Kim, Chil Seong Ah, and Chihun Sung
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Materials science ,Colored ,Mechanics of Materials ,business.industry ,Optoelectronics ,General Materials Science ,Electrochromic devices ,business ,Industrial and Manufacturing Engineering ,Fabry–Pérot interferometer ,Indium tin oxide - Published
- 2020
14. Electrochromic Infrared Light Modulation in Optical Waveguides
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Jin Tae Kim, Juhee Song, Chil Seong Ah, and Hojun Ryu
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Materials science ,Electrochromism ,Modulation ,business.industry ,Infrared ,Optoelectronics ,Electrochromic devices ,business ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials - Published
- 2019
15. Graphene Electrode Enabling Electrochromic Approaches for Daylight-Dimming Applications
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Yong-Hae Kim, Seungmin Cho, Joo Yeon Kim, Chi-Sun Hwang, Jeong-Ik Lee, Chil Seong Ah, Nam Sung Cho, Tae-Youb Kim, Sujung Kim, Sang-Hoon Cheon, Ji-Young Oh, Seong M. Cho, Seung-Youl Kang, Hojun Ryu, Kisoo Kim, and Kyuwon Kim
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Fabrication ,Materials science ,Oxide ,lcsh:Medicine ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,Electrochromic devices ,01 natural sciences ,Article ,law.invention ,chemistry.chemical_compound ,PEDOT:PSS ,law ,lcsh:Science ,Multidisciplinary ,business.industry ,Graphene ,lcsh:R ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,Electrochromism ,Electrode ,Optoelectronics ,lcsh:Q ,0210 nano-technology ,business ,Indium - Abstract
For environmental reason, buildings increasingly install smart windows, which can dim incoming daylight based on active electrochromic devices (ECDs). In this work, multi-layered graphene (MLG) was investigated as an ECD window electrode, to minimize carbon dioxide (CO2) emissions by decreasing the electricity consumption for building space cooling and heating and as an alternative to the transparent conductor tin-doped indium oxide (ITO) in order to decrease dependence on it. Various MLG electrodes with different numbers of graphene layers were prepared with environmentally friendly poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) to produce ECD cells. Tests demonstrated the reproducibility and uniformity in optical performance, as well as the flexibility of the ECD fabrication. With the optimized MLG electrode, the ECD cells exhibited a very fast switching response for optical changes from transparent to dark states of a few hundred msec.
- Published
- 2018
16. Highly conductive and environmentally stable gold/graphene yarns for flexible and wearable electronics
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Hae Jin Kim, Jong Ho Shin, Yong Ju Yun, Yongseok Jun, Won G. Hong, and Chil Seong Ah
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Materials science ,Graphene ,business.industry ,Nanotechnology ,02 engineering and technology ,Bending ,Conductivity ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,law ,Electrical resistivity and conductivity ,Colloidal gold ,Gravimetric analysis ,General Materials Science ,0210 nano-technology ,business ,Electrical conductor ,Wearable technology - Abstract
Here, we fabricated high-performance gold/graphene yarns through a facile method by the electroless deposition of gold nanoparticles onto the surface of graphene yarns. The gold/graphene yarns are fabricated using a completely solution-based process that can be scaled up for practical applications. They possess high electrical conductivity (2.86 × 102 S cm-1) and good gravimetric specific conductivity (6.81 × 102 S cm2 g-1) as well as good reliability under 1000 bending tests with a maximum bending angle of 170° and 10 washing tests with laundry detergents. These stable conducting yarns could also be integrated into textiles and clothes in various forms to create smart fabrics and wearable devices. In addition, this facile approach is easily applicable to various graphene films and devices on soft substrates that are presently used in flexible/wearable electronics.
- Published
- 2017
17. Electrochromic device for the reversible electrodeposition system
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Tae-Youb Kim, Hye Yong Chu, Chil Seong Ah, Hojun Ryu, Seong M. Cho, and Kyung-Soo Suh
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Materials science ,business.industry ,Dynamic range ,Honeycomb structure ,Wavelength ,Optics ,Electrochromism ,Transmittance ,Optoelectronics ,General Materials Science ,Electrical and Electronic Engineering ,business ,Deposition (law) ,Voltage - Abstract
A novel silver (Ag) deposition-based electrochromic device was developed for the reversible electrodeposition (RED) system. The electrochromic device can switch between transparent and mirror states in response to a change in the applied voltage. The dynamic range of the transmittance percent (%) for the fabricated device was about 90% at the 550 nm wavelength. A large-area RED display system was also successfully fabricated using the parted electrochromic cells of the honeycomb structure. The interelectrode space and the extent of the large-area RED display system were 50 μm and 10×10 cm, respectively.
- Published
- 2014
18. Colorimetric quantitative sensing of alkali metal ions based on reversible assembly and disassembly of gold nanoparticles
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Wan Soo Yun, Chil Seong Ah, Sang-Woo Joo, and Wan-Joong Kim
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Ionic radius ,Chemistry ,Inorganic chemistry ,General Physics and Astronomy ,Nanoparticle ,Alkali metal ,Ion ,Metal ,Colloid ,Colloidal gold ,Color changes ,visual_art ,visual_art.visual_art_medium ,General Materials Science - Abstract
A novel and simple method for the colorimetric quantitative sensing of individual alkali metal ions (Li + , Na + , K + , and Rb + ) based on the reversible properties of self-assembled aggregates and individual gold nanoparticles (Au NPs) is described. This paper demonstrates reversible self-assembly processes where the degree of assembly and disassembly is dependent on the individual alkali metal ion concentration, nanoparticle size, and alkali metal ionic radii. The color changes of the colloidal Au NPs with metal ion concentrations in colloidal NP solutions occur reversibly. Below a certain concentration of alkali metal ions, the aggregates of Au NPs are redispersed. As the Au NP diameters and the alkali metal ionic radii increase, the critical concentration decreases.
- Published
- 2013
19. Switchable Holographic Device Based on Reversible Electrodeposition
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Yong-Hae Kim, Jeong-Ik Lee, Joo Yeon Kim, Seong M. Cho, Tae-Youb Kim, Chi-Young Hwang, Juhee Song, Sujung Kim, Chil Seong Ah, Chi-Sun Hwang, Sang Hoon Cheon, and Hojun Ryu
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Materials science ,Spatial light modulator ,business.industry ,Holography ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Industrial and Manufacturing Engineering ,0104 chemical sciences ,law.invention ,Mechanics of Materials ,law ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business - Published
- 2018
20. Photo selective protein immobilization using bovine serum albumin
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Jongcheol Hong, Chil Seong Ah, Chan Woo Park, Chul Huh, Wan-Joong Kim, Bong Kyu Kim, Jong-Heon Yang, Yo Han Choi, Kwang Hyo Chung, Ansoon Kim, and Gun Yong Sung
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Materials science ,Chromatography ,biology ,General Physics and Astronomy ,Substrate (chemistry) ,Surfaces and Interfaces ,General Chemistry ,Condensed Matter Physics ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,chemistry ,Ellipsometry ,Diazirine ,biology.protein ,Fluorescence microscope ,Molecule ,Bovine serum albumin ,Bifunctional ,Protein adsorption - Abstract
A simple and selective technique which immobilizes protein onto a solid substrate by using UV illumination has been developed. In protein immobilization, a Bovine serum albumin (BSA) performed bifunctional role as a cross-linker between substrate and proteins and as a blocker inhibiting a nonspecific protein adsorption. A new photo-induced protein immobilization process has been investigated at each step by fluorescence microscopy, ellipsometry, and Fourier transform infrared (FT-IR) spectroscopy. A UV photomask has been used to induce selective protein immobilization on target regions of the surface of the SiO2 substrates under UV illumination with negligible nonspecific binding. The UV illumination also showed improved photostability than the conventional methods which employed bifunctional photo-crosslinker molecules of photo-reactive diazirine. This new UV illumination-based photo-addressable protein immobilization provides a new approach for developing novel protein microarrays for multiplexed sensing as well as other types of bio-immobilization in biomedical devices and biotechnologies.
- Published
- 2012
21. Design and Fabrication of Integrated Fabry-Perot Type Color Reflector for Reflective Displays
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Sang Hoon Cheon, Hojun Ryu, Seong M. Cho, Chil Seong Ah, Juhee Song, Tae-Youb Kim, and Hye Yong Chu
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Materials science ,Fabrication ,business.industry ,Biomedical Engineering ,Bioengineering ,Reflector (antenna) ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,010309 optics ,Wavelength ,NTSC ,Gamut ,Optics ,0103 physical sciences ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business ,Deposition (law) ,Fabry–Pérot interferometer ,Visible spectrum - Abstract
A Fabry-Perot type integrated color reflector, with red/blue/green colors as subpixels, was designed and fabricated with Si substrate. Ag films were used as reflective mirror layers, SiO2 films were used as Fabry-Perot cavity layers and W films were used as partially reflective layers for the cavity. To minimize the effects of the thickness variation of the oxide cavity layers, the structure of the color reflector was optimized, and the differential deposition scheme was devised and applied in the fabrication process. The integrated color reflector was successfully fabricated with the proposed fabrication scheme. The measured white reflectance was > 45% in the visible spectrum range and -49% at 550 nm wavelength. The fabricated reflector had moderate color gamut of 17% of the National Television System Committee (NTSC) standard and it showed very high white reflectivity. The fabricated color reflector is expected to be applicable to reflective displays.
- Published
- 2016
22. Effects of Pre-reducing Sb-Doped SnO2 Electrodes in Viologen-Anchored TiO2 Nanostructure-Based Electrochromic Devices
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Yong-Hae Kim, Chil Seong Ah, Juhee Song, Seong M. Cho, Joo Yeon Kim, Sang Hoon Cheon, Chi-Sun Hwang, Ho Jun Ryu, and Tae Youb Kim
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Materials science ,Nanostructure ,General Computer Science ,business.industry ,Doping ,Viologen ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochromic devices ,01 natural sciences ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Electrochromism ,Electrode ,medicine ,Optoelectronics ,Electrical and Electronic Engineering ,0210 nano-technology ,business ,medicine.drug - Published
- 2016
23. Detection of uncharged or feebly charged small molecules by field-effect transistor biosensors
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Joon Sung Lee, Wan-Joong Kim, Gun Yong Sung, Jong-Heon Yang, Kwang Hyo Chung, Chan Woo Park, Chil Seong Ah, Yo Han Choi, Jungho Kim, and In Bok Baek
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Aflatoxin B1 ,Transistors, Electronic ,Chemistry ,Transistor ,Biomedical Engineering ,Biophysics ,Analytical chemistry ,Metal Nanoparticles ,Ionic bonding ,Nanoparticle ,Biosensing Techniques ,General Medicine ,Ochratoxins ,Small molecule ,law.invention ,Isoelectric point ,law ,Electrochemistry ,Zearalenone ,Molecule ,Field-effect transistor ,Gold ,Biosensor ,Biotechnology - Abstract
This paper describes a new technique for the detection of uncharged or feebly charged small molecules (
- Published
- 2012
24. Analysis of configuration of surface-immobilized proteins by Si nanochannel field effect transistor biosensor
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Chil Seong Ah, Gun Yong Sung, Chan Woo Park, Chang-Geun Ahn, Jong-Heon Yang, Ansoon Kim, and Tae-Youb Kim
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Field effect transistor ,Chemistry(all) ,Analytical chemistry ,Salt (chemistry) ,chemistry.chemical_compound ,symbols.namesake ,Materials Chemistry ,Molecule ,Immobilized proteins ,Electrical and Electronic Engineering ,Instrumentation ,Debye length ,chemistry.chemical_classification ,Chemistry ,Metals and Alloys ,Conductance ,General Medicine ,Buffer solution ,Top-down ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Ionic strength ,Si nanochannel ,Chemical Engineering(all) ,symbols ,Field-effect transistor ,Counterion ,Biosensor - Abstract
We demonstrate the application of ‘top-down’ fabricated Si nanochannel field effect transistor biosensors in measuring the configuration of charged proteins immobilized on the Si surface. We have immobilized monoclonal antibodies of PSA (anti-PSA) on the p-type Si channel surface, and monitored the channel conductance in response to the variation of ionic strength (salt concentration) and pH level of the buffer solution. The dependency of channel conductance on the salt concentration is consistent with the screening of protein charges by dissolved counterions, enabling quantitative estimation of the distance from the Si surface to anti-PSA molecules based on calculated Debye screening lengths (λD) for each salt concentration. The effect of salt concentration on the pH-dependency of channel conductance has also been studied, and explained in terms of the net charge of anti-PSA as a function of pH.
- Published
- 2011
25. Response to Cardiac Markers in Human Serum Analyzed by Guided-Mode Resonance Biosensor
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Jongcheol Hong, Chil Seong Ah, Ansoon Kim, Junghan Song, Bong Kyu Kim, Seon Hee Park, Wan-Joong Kim, Sanghoon Song, Kyung-Hyun Kim, Gun Yong Sung, and Chul Huh
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Detection limit ,Cardiac troponin ,Chromatography ,Immobilized enzyme ,Myoglobin ,Chemistry ,Photoelectron Spectroscopy ,Troponin I ,Immobilized Antibodies ,Biosensing Techniques ,Immunogold labelling ,Analytical Chemistry ,chemistry.chemical_compound ,Creatine Kinase, MB Form ,Humans ,Gold ,Antibodies, Immobilized ,Biosensor ,Biomarkers - Abstract
Cardiac markers in human serum with concentrations less than 0.1 ng/mL were analyzed by use of a guided-mode resonance (GMR) biosensor. Cardiac troponin I (cTnI), creatine kinase MB (CK-MB), and myoglobin (MYO) were monitored in the serum of both patients and healthy controls. Dose-response curves ranging from 0.05 to 10 ng/mL for cTnI, from 0.1 to 10 ng/mL for CK-MB, and from 0.03 to 1.7 μg/mL for MYO were obtained. The limits of detection (LOD) for cTnI, CK-MB, and MYO were less than 0.05, 0.1, and 35 ng/mL, respectively. Analysis time was 30 min, which is short enough to meet clinical requirements. Antibody immobilization and the hydrophilic properties of the guided-mode resonance filter (GMRF) surface were investigated by X-ray photoelectron spectroscopy (XPS) and by monitoring the peak wavelength shift and water contact angle (CA). Both assays used to evaluate the surface density of the immobilized antibodies, a sandwich enzyme-linked immunosorbent assay (ELISA) and a sandwich immunogold assay, showed that the antibodies were successfully immobilized and sufficiently aligned to detect the low concentration of biomarkers. Our results show that the GMR biosensor will be very useful in developing low-cost portable biosensors that can screen for cardiac diseases.
- Published
- 2010
26. Electronic Detection of Biomarkers by Si Field-Effect Transistor from Undiluted Sample Solutions with High Ionic Strengths
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Jong-Heon Yang, Chil Seong Ah, Chang-Geun Ahn, Gun Yong Sung, Tae-Youb Kim, Chan Woo Park, Ansoon Kim, Wan-Joong Kim, and In Bok Baek
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Ionic strength ,Chemistry ,Phosphate buffered saline ,Analytical chemistry ,Ionic bonding ,Direct monitoring ,Field-effect transistor ,General Chemistry ,Biosensor ,Dilution - Abstract
In this study, we have developed a new detection method using Si field effect transistor (FET)-type biosensors, which enables the direct monitoring of antigen-antibody binding within very high-ionic-strength solutions such as 1×PBS and human serum. In the new method, as no additional dilution or desalting processes are required, the FET-type biosensors can be more suitable for ultrasensitive and real-time analysis of raw sample solutions. The new detection scheme is based on the observation that the strength of antigen-antibody-specific binding is significantly influenced by the ionic strength of the reaction solutions. For a prostate specific antigen (PSA), in some conditions, the binding reaction between PSA and anti-PSA in a low-ionic strength reaction solution such as 10 µM phosphate buffer is weak (reversible), while that in high-ionic strength reaction solutions such as 1×PBS or human serum is strong.
- Published
- 2010
27. Fabrication of Anionic Sulfate-Functionalized Nanoparticles as an Immunosensor by Protein Immobilization
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Chil Seong Ah, Wan-Joong Kim, Ansoon Kim, Sungho Ko, Hyeon-Bong Pyo, and Sanghee Kim
- Subjects
Anions ,Surface Properties ,Analytical chemistry ,Emulsion polymerization ,Nanoparticle ,Antibodies ,Antigen-Antibody Reactions ,chemistry.chemical_compound ,X-ray photoelectron spectroscopy ,Electrochemistry ,Zeta potential ,Humans ,Bicinchoninic acid assay ,General Materials Science ,Particle Size ,Spectroscopy ,Immunoassay ,Sulfates ,Troponin I ,Models, Immunological ,Surfaces and Interfaces ,Potassium persulfate ,Condensed Matter Physics ,chemistry ,Immunoglobulin G ,Nanoparticles ,Polystyrenes ,Particle ,Polystyrene ,Nuclear chemistry - Abstract
Anionic sulfate (SO(4)(-))-functionalized polystyrene (PS) nanoparticles were prepared by the thermal decomposition of potassium persulfate (KPS) in the presence of sodium tetraborate via emulsion polymerization. The presence of a SO(4)(-) group at a solid/liquid interface of a particle surface was confirmed by a zeta potential value of -40.6 mV as well as the shifting of S 2p spectra toward a lower-binding-energy region around 162.7 eV (2p(3/2)) and 164.4 eV (2p(1/2)) in X-ray photoelectron spectroscopy (XPS) analysis. The electrostatic attraction between positively charged antibodies of human immunoglobulin G (hIgG) and cardiac troponin I (cTnI) and negatively charged particle surfaces was accomplished. The atomic force microscopy (AFM) measurement and bicinchoninic acid (BCA) assay results show binding structure between hIgG and antibodies of hIgG (anti-hIgG) with a gradual increase in particle diameter to 152.6 nm (bare), 170.2 nm (hIgG), and 178.9 nm (hIgG/anti-hIgG). Surface coverage densities of 331.4 ng/cm(2) (hIgG) and 320.3 ng/cm(2) (cTnI) and the binding capacity of hIgG to HyLite-750-labeled Fab-specific anti-hIgG (approximately 81.2%) indicate that the majority of hIgG was immobilized with a Y-shaped orientation. The sandwich immunoassay results provide the evidence that the immunological activity of cTnI on the PS nanoparticle surface was retained because the binding activity of the cTnI-PS nanoparticle/cTnI (antigen)/detection cTnI-antibody reaction showed a 5-fold higher activity than that of the cTnI-PS nanoparticle/human serum albumin (HSA)/detection cTnI antibody used as a negative control.
- Published
- 2010
28. Direct label-free electrical immunodetection in human serum using a flow-through-apparatus approach with integrated field-effect transistors
- Author
-
Chan Woo Park, Ansoon Kim, Chil Seong Ah, Tae-Youb Kim, Gun Yong Sung, Jong-Heon Yang, Chang-Geun Ahn, and Sun Hee Park
- Subjects
Conductometry ,Transistors, Electronic ,Point-of-care testing ,Biomedical Engineering ,Biophysics ,Nanotechnology ,Biosensing Techniques ,Proteomics ,Sensitivity and Specificity ,Sensor array ,Biomarkers, Tumor ,Electrochemistry ,Humans ,Cancer marker ,Label free ,Immunoassay ,Staining and Labeling ,Drug discovery ,Chemistry ,Reproducibility of Results ,Equipment Design ,General Medicine ,Carcinoembryonic Antigen ,Equipment Failure Analysis ,Systems Integration ,Flow Injection Analysis ,Field-effect transistor ,Biosensor ,Blood Chemical Analysis ,Biotechnology ,Biomedical engineering - Abstract
In order to identify changes in the levels of key proteins in response to the onset or development of a disease, the research fields of proteomics and genomics seek to develop new biomarkers. Specifically, simple and fast biomarker screens have a central role in many areas of healthcare, including disease diagnosis and drug discovery. Biologically modified field-effect transistor (BioFET) is one of the most attractive approaches because of the on-chip integration of the sensor array, fast response, high reliability and low-cost mass production. However, the BioFETs used to detect macromolecules have been operated only in buffer solution with low salt concentrations because of the Debye screening length of blood or serum. Here we report a novel detection technique for direct label-free immunodetection of cancer markers in human serum using a Si-FET that was fabricated by conventional photolithographic processes. The proposed sensing method shows no dissociation of antigen-antibody binding as in general immunoassays, unlike the previous reports on Si-FET sensors. This method therefore overcomes the Debye length problem of immunodetection in human fluids, such as serum, that are generally encountered by FET-based biosensors. Our results demonstrate specific label-free and real-time immunodetection of a cancer marker at a concentration of 0.2 ng/mL in human serum, quantitative detection of the marker from 0.2 to 114 ng/mL, and successful multiplexed sensing of three different cancer markers. We believe that connecting our simple electrical detection method, which does not require pretreatment of serum, with well-established whole blood filter technology will contribute to the development of new point-of-care testing (POCT) sensors.
- Published
- 2010
29. Laser-induced mutual transposition of the core and the shell of a Au(at the rate)Pt nanosphere
- Author
-
Chil Seong Ah, Seol Ji Kim, and Du-Jeon Jang
- Subjects
Gold compounds -- Chemical properties ,Gold compounds -- Thermal properties ,Platinum -- Chemical properties ,Platinum -- Thermal properties ,Laser photochemistry -- Research ,Chemicals, plastics and rubber industries - Abstract
The mutual transportation of the core and the shell of a Au(at the rate)Pt core-shell nanosphere is obtained by using picosecond laser pulses to excite the surface-plasmon resonances of platinum. The thermalized photon energy of platinum-plasmon resonances induces the core metal of gold having the lower melting temperature to melt and soak out to the surface to become the shell metal of a newly formed Pt(at the rate)Au core-shell nanosphere.
- Published
- 2006
30. Effects of pH and Ion Concentration in Phosphate Buffer Solution on the Sensitivity of the Silicon Nanowire BioFETs
- Author
-
Gun Yong Sung, Chang-Guen Ahn, Jaehyun Lee, Chan Woo Park, Mincheol Shin, and Chil Seong Ah
- Subjects
symbols.namesake ,Materials science ,Nanosensor ,Phosphate buffered saline ,Analytical chemistry ,symbols ,General Physics and Astronomy ,Nanotechnology ,Sensitivity (control systems) ,Silicon nanowires ,Debye length ,Ion - Published
- 2009
31. Nanogap Array Fabrication Using Doubly Clamped Freestanding Silicon Nanowires and Angle Evaporations
- Author
-
In-Bok Baek, Byung Hoon Kim, Chang-Guen Ahn, Ansoon Kim, Chan Woo Park, Chil Seong Ah, Jong-Heon Yang, and Han Young Yu
- Subjects
Fabrication ,Materials science ,General Computer Science ,Silicon dioxide ,Semiconductor device fabrication ,Transistor ,Nanowire ,Nanoparticle ,Molecular electronics ,Nanotechnology ,Evaporation (deposition) ,Electronic, Optical and Magnetic Materials ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Electrical and Electronic Engineering - Abstract
We present a simple semiconductor process to fabricate nanogap arrays for application in molecular electronics and nano-bio electronics using a combination of freestanding silicon nanowires and angle evaporation. The gap distance is modulated using the height of the silicon dioxide, the width of the Si nanowires, and the evaporation angle. In addition, we fabricate and apply the nanogap arrays in single-electron transistors using DNA-linked Au nanoparticles for the detection of DNA hybridization.
- Published
- 2009
32. Spatially Selective Immobilization of Functional Materials onto Silicon Surfaces Using Electrochemical Method
- Author
-
Kyuwon Kim, Chil-Seong Ah, and Soo-Hyoun Park
- Subjects
Materials science ,Silicon ,chemistry ,Colloidal gold ,Nanowire ,Molecule ,chemistry.chemical_element ,Nanoparticle ,Nanotechnology ,Electrochemistry ,Deposition (law) ,Nanowire array - Abstract
We present a method for spatially selective immobilization of functional materials, such as proteins and nanoparticles, onto pre-activated silicon surfaces by electrochemical reaction. Carboxymethylbenzendiazonium (CMBD) cations, being adsorbable on silicon surfaces through electrochemically reductive deposition, is used as an anchor molecule to prepare the pre-activated silicon surfaces. It is demonstrated that the use of BD reaction is very efficient for the selective immobilization because the functional materials are immobilized exclusively onto the pre-adsorbed CMBD region. The method is applied to immobilize gold nanoparticles on the selected nanowire of the nanowire array.
- Published
- 2009
33. Colorimetric Analysis on Flocculation of Bioinspired Au Self-Assembly for Biophotonic Application
- Author
-
Wan Soo Yun, Jasmine Austin, Shanghee Kim, Ansoon Kim, Jaetae Seo, Gun Yong Sung, Chil Seong Ah, and Wan-Joong Kim
- Subjects
Materials science ,Article Subject ,Absorption spectroscopy ,Surface plasmon ,Physics::Optics ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Colloidal gold ,lcsh:Technology (General) ,lcsh:T1-995 ,General Materials Science ,Self-assembly ,0210 nano-technology ,Absorption (electromagnetic radiation) ,Colorimetric analysis ,Plasmon ,Localized surface plasmon - Abstract
Gold nanoparticles exhibited strong surface plasmon absorption and couplings between neighboring particles within bioactivated self-assembly modified their optical properties. Colorimetric analysis on the optical modification of surface plasmon resoanance (SPR) shift and flocculation parameter functionalized bioinspired gold assembly for biophotonic application. The physical origin of bioinspired gold aggregation-induced shifting, decreasing, or broadening of the plasmon absorption spectra could be explained in terms of dynamic depolarization, collisional damping, and shadowing effects.
- Published
- 2009
34. Excited-state tautomerization dynamics of 7-hydroxyquinoline in beta-cyclodextrin
- Author
-
Han Jung Park, Oh-Hoon Kwon, Chil Seong Ah, and Du-Jeon Jang
- Subjects
Cyclodextrins -- Chemical properties ,Quinoline -- Chemical properties ,Excited state chemistry -- Research ,Chemicals, plastics and rubber industries - Abstract
The excited-state tautomerization dynamics of 7-hydroxyquinoline in beta-cyclodextrin is compared with that in pure water by measuring isotope-dependent fluorescence kinetics as well as absorption and emission spectra. The normal species tautomerizes stepwise via forming anionic intermediate species in both systems.
- Published
- 2005
35. Laser-induced growth and reformation of gold and silver nanoparticles
- Author
-
Du-Jeon Jang, Seol Ji Kim, and Chil Seong Ah
- Subjects
Materials science ,Polyvinylpyrrolidone ,Nucleation ,Nanoparticle ,Bioengineering ,Nanotechnology ,General Chemistry ,Condensed Matter Physics ,Laser ,Atomic and Molecular Physics, and Optics ,Silver nanoparticle ,law.invention ,Metal ,Colloid ,Chemical engineering ,law ,Modeling and Simulation ,visual_art ,visual_art.visual_art_medium ,medicine ,General Materials Science ,Irradiation ,medicine.drug - Abstract
The sizes, shapes, and growth rates of gold and silver nanoparticles stabilized with polyvinylpyrrolidone in water can be controlled by using picosecond laser pulses. The nucleation of small metal clusters formed with NaBH4 addition to produce nanoparticles takes two months with aging but 30 min with laser irradiation. Laser pulses can also induce nanoparticles to have narrow size and shape distribution or to undergo aggregation into much larger particles. The latter process is more likely found when the metal is silver or the irradiation wavelength is short. Laser-induced growth and shape transformation processes are explained in terms of BH4− depletion, metal fusion, and electron ejection followed by disintegration.
- Published
- 2008
36. Shape Transformation and Relaxation Dynamics of Photoexcited TiO2/Ag Nanocomposites
- Author
-
Dongha Shin, Mee Rahn Kim, Chil Seong Ah, Du-Jeon Jang, Sang Kyung Lee, and Wan In Lee
- Subjects
Materials science ,Nanocomposite ,Relaxation (NMR) ,Biomedical Engineering ,Sintering ,Bioengineering ,General Chemistry ,Electron ,Condensed Matter Physics ,Silver nanoparticle ,Adsorption ,Chemical engineering ,Computational chemistry ,Photocatalysis ,General Materials Science ,Surface states - Abstract
The laser-induced sintering of TiO2 nanoparticles into larger nanospheres is accelerated by adsorbed silver particles. For the same weight fraction of silver, silver nanoparticles of 5 nm in diameter modify TiO2 nanoparticles more effectively than those of 1.5 nm do, suggesting that the photocatalysis of TiO2 nanoparticles as well as their stability is highly dependent on the sizes, the shapes, and the distribution of adsorbed metal nanoparticles. The photoexcited electrons of TiO2 nanoparticles are quenched at trap sites and surface states by transfer to the conduction band of silver, implying that the presence of adsorbed silver nanoparticles enhances the photocatalytic effect of TiO2.
- Published
- 2008
37. Photolysis dynamics of benzyl phenyl sulfide adsorbed on silver nanoparticles
- Author
-
Seol Ji Kim, Taeg Gyum Kim, Chil Seong Ah, Kwan Kim, and Du-Jeon Jang
- Subjects
Water chemistry -- Research ,Radicals (Chemistry) -- Research ,Chemicals, plastics and rubber industries - Abstract
Results obtained with time-resolved transient-absorption spectroscopy to show the detailed photoreaction mechanism of BPS adsorbed on silver nanoparticles suspended in water is discussed. The benzenethiolate combines to the metallic surface of a silver nanoparticle in 30 ns while the benzyl radical abstracts atomic hydrogen from water in 130 ns to form toluence.
- Published
- 2004
38. Optical Fabrication of Hollow Platinum Nanospheres by Excavating the Silver Core of Ag@Pt Nanoparticles
- Author
-
Chil Seong Ah, Seol Ji Kim, and Du-Jeon Jang
- Subjects
Core (optical fiber) ,Fabrication ,Materials science ,chemistry ,Mechanics of Materials ,Mechanical Engineering ,chemistry.chemical_element ,General Materials Science ,Nanotechnology ,Surface plasmon resonance ,Pt nanoparticles ,Platinum - Published
- 2007
39. Temperature-induced control of aspect ratio of gold nanorods
- Author
-
Chil Seong Ah, Kwang-Pil Lee, Hyung Ju Park, Wan Soo Yun, Wan-Joong Kim, and Insung S. Choi
- Subjects
Materials science ,Aqueous solution ,Hydrogen ,Aspect ratio ,Inorganic chemistry ,Nanowire ,food and beverages ,chemistry.chemical_element ,Nanoparticle ,Surfaces and Interfaces ,Condensed Matter Physics ,Ascorbic acid ,Silver nanoparticle ,Surfaces, Coatings and Films ,chemistry ,Nanorod - Abstract
Aspect ratio of gold nanorods can be controlled by simply adjusting the reaction temperature in the seed-mediated synthesis of the nanorods. The gold nanorods were synthesized by the injection of gold nanoparticle seeds of around 4nm in diameter into a reaction mixture containing hydrogen tetrachloroaurate, hexadecyltrimethylammonium bromide, and ascorbic acid. Average aspect ratio of the resulting nanorod increases from 1 to about 40 with decreasing the reaction temperature from 315to276K, which can be attributed to the temperature-induced change in the shape of the micellar templates. For further understanding of the growth mechanism, silver nanoparticles were also used as seeds in the preparation of the gold nanorod.
- Published
- 2006
40. Fabrication of Movable Nanostructures by Selective Etching of Nanoplates
- Author
-
Wan Soo Yun, Chil-Seong Ah, Dong Han Ha, and Yong-Ju Yun
- Subjects
Nanostructure ,Materials science ,Fabrication ,Etching (microfabrication) ,Mechanical Engineering ,Nanotechnology - Published
- 2006
41. Size-Controlled Synthesis of Machinable Single Crystalline Gold Nanoplates
- Author
-
Chil Seong Ah, Wan Soo Yun, Hyung Ju Park, Yong Ju Yun, Wan-Joong Kim, and and Dong Han Ha
- Subjects
Materials science ,Hydrogen ,General Chemical Engineering ,Surface plasmon ,technology, industry, and agriculture ,chemistry.chemical_element ,Nanotechnology ,General Chemistry ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Molar ratio ,Sodium citrate ,Materials Chemistry ,Absorption (chemistry) - Abstract
Monodispersive size-controlled gold nanoplates were synthesized with high purity from the reduction of hydrogen tetrachloroaurate by reduced amount of sodium citrate, which kinetically controls the reaction pathway, in the presence of poly(vinyl pyrrolidone) (PVP). With the insufficient addition of the reductant, the molar ratio of sodium citrate and PVP relative to hydrogen tetrachloroaurate played an important role in determining the geometric shape and size of the product. These nanoplates were single crystals with planar width of 80−500 nm and thickness of 10−40 nm, exhibiting strong surface plasmon absorption in the near-infrared (NIR) region of 700−2000 nm. The gold nanoplates were used as the synthetically provided nanoblocks to fabricate single-crystalline nanocomponents, such as a nanoscaled gear or a nanoscaled letter.
- Published
- 2005
42. Excited-State Tautomerization Dynamics of 7-Hydroxyquinoline in β-Cyclodextrin
- Author
-
Chil Seong Ah, Han Jung Park, Du-Jeon Jang, and Oh-Hoon Kwon
- Subjects
chemistry.chemical_classification ,Cyclodextrin ,beta-Cyclodextrins ,Kinetics ,Photochemistry ,Fluorescence ,Tautomer ,Surfaces, Coatings and Films ,Isomerism ,chemistry ,Fluorescence kinetics ,Excited state ,Quinolines ,Materials Chemistry ,Emission spectrum ,Physical and Theoretical Chemistry ,Charged species - Abstract
The excited-state tautomerization dynamics of 7-hydroxyquinoline encapsulated in beta-cyclodextrin is compared with that in pure water by measuring isotope-dependent fluorescence kinetics as well as absorption and emission spectra. The normal species tautomerizes stepwise via forming anionic intermediate species in both systems. However, the enol-deprotonation time (40 ps in water) becomes as large as 170 ps whereas the imine-protonation time of the anionic intermediate (160 ps in water) becomes as short as 85 ps in beta-cyclodextrin. The slow formation and the fast decay of the anionic species are attributed to the unstability of the charged species in hydrophobic cages. Encapsulation can be utilized to enhance fluorescence enormously and to accelerate selective reactions by retarding other processes.
- Published
- 2005
43. Preparation of Au(sub core)Ag(sub shell) nanorods and characterization of their surface plasmon resonances
- Author
-
Chil Seong Ah, Seung Do Hong, and Du Jeon Jang
- Subjects
Silver compounds -- Spectra ,Gold compounds -- Spectra ,Chemicals, plastics and rubber industries - Abstract
The study reports that Au(sub core)Ag(sub shell) nanorods (NRs) can be prepared and that the surface plasmon absorption of silver NRs has been experimentally characterized. The results revealed that the surface gold NRs has been coated with silver by reducing AgCl(super 3-)(sub 4) exclusively on the metallic surface and then restored by removing the silver coating only.
- Published
- 2001
44. Formation and Distinctive Decay Times of Surface- and Lattice-Bound Mn2+ Impurity Luminescence in ZnS Nanoparticles
- Author
-
Du-Jeon Jang, Jae Hun Chung, and and Chil Seong Ah
- Subjects
Physics::General Physics ,Materials science ,Condensed matter physics ,Astrophysics::High Energy Astrophysical Phenomena ,Nanoparticle ,Kinetic energy ,Molecular physics ,Surfaces, Coatings and Films ,Condensed Matter::Materials Science ,Impurity ,Condensed Matter::Superconductivity ,Lattice (order) ,Ultrafast laser spectroscopy ,Materials Chemistry ,Condensed Matter::Strongly Correlated Electrons ,Physical and Theoretical Chemistry ,Luminescence - Abstract
The Mn2+ impurity luminescence decay of Mn2+-doped ZnS nanoparticles has been clearly distinguished from ZnS host emission decay by measuring transient absorption and emission kinetic profiles in t...
- Published
- 2001
45. Photofragmentation Dynamics of n-Dodecanethiol-Derivatized Silver Nanoparticles in Cyclohexane
- Author
-
Hyouk Soo Han, Du-Jeon Jang, and Kwan Kim, and Chil Seong Ah
- Subjects
Cyclohexane ,Chemistry ,Photodissociation ,Analytical chemistry ,Photon energy ,Photochemistry ,Silver nanoparticle ,Surfaces, Coatings and Films ,Nanoclusters ,chemistry.chemical_compound ,Excited state ,Ultrafast laser spectroscopy ,Materials Chemistry ,Physical and Theoretical Chemistry ,Absorption (electromagnetic radiation) - Abstract
Photochemical reaction of n-dodecanethiol-derivatized silver nanoclusters dispersed in cyclohexane has been studied in the picosecond−second time range and has been found to depend nonlinearly on the irradiance of photolysis light. The static absorption bleach by excitation at 532 and 355 nm increases with the irradiance raised to the powers of 1.9 and 1.4, respectively. Furthermore, transient absorption produced with a high-energy pulse rises further on a time scale of a few nanoseconds, whereas that with low-energy pulse decays. Transient absorption owing to the dielectric change of the immediately surrounding medium arises in 0.5 ns with the conduction of the thermalized photon energy. It decays in 1.4 ns as the heat spreads further. A fraction of excited nanoparticles experience a further absorption increase as hot alkanethiols dissociate for a period determined by the heat dissipation time (3.6 ns). The fraction increases with excitation-pulse energy. Within the recombination time (40 ns) of thiols, ...
- Published
- 2000
46. Preparation, Characterization, and Photolysis of Dodecanethiol-Derivatized Noble Metal Nanoparticles
- Author
-
Chil Seong Ah, Kwan Kim, Du-Jeon Jang, and Hyouk Soo Han
- Subjects
Cyclohexane ,Chemistry ,Photodissociation ,Inorganic chemistry ,Nanoparticle ,engineering.material ,Condensed Matter Physics ,Photochemistry ,Silver nanoparticle ,chemistry.chemical_compound ,Transition metal ,engineering ,Flash photolysis ,Noble metal ,Absorption (chemistry) - Abstract
Dodecanethiol-derivatized nanoparticles of Ag, Ag/Au, and Au with an average size of 5.5 nm have been prepared via a two-phase synthetic route in water/toluene and characterized with various methods. In particular, their photochemical dynamics and mechanisms have been studied with laser flash photolysis. The surface plasmon absorption peak varies linearly from 532 to 429 nm as the Ag fraction of Ag/Au alloy clusters, in which Ag atoms are more abundant at the outer part, increases. Excited silver nanoparticles dispersed in cyclohexane undergo dethiolation in 8 ns and then fragmentation in 40 ns. Thereafter, the fragments gradually aggregate owing to the presence of less soluble bare metal sides.
- Published
- 1999
47. Photolysis Dynamics of Benzyl Phenyl Sulfide Adsorbed on Silver Nanoparticles
- Author
-
Du-Jeon Jang, Seol Ji Kim, and Kwan Kim, Taeg Gyum Kim, and Chil Seong Ah
- Subjects
Hydrogen ,Photodissociation ,chemistry.chemical_element ,Photochemistry ,Toluene ,Silver nanoparticle ,Surfaces, Coatings and Films ,Metal ,chemistry.chemical_compound ,Adsorption ,chemistry ,visual_art ,Materials Chemistry ,visual_art.visual_art_medium ,Physical and Theoretical Chemistry ,Spectroscopy ,Excitation - Abstract
The photolysis dynamics of benzyl phenyl sulfide adsorbed on silver nanoparticles suspended in water has been studied by using time-resolved transient-absorption spectroscopy. The adsorbed molecule desorbs from the metallic surface with a photoejected electron within 2 ns after excitation. The anionic species dissociates into benzenethiolate and benzyl radical on the time scale of 8 ns. The benzenethiolate combines to the metallic surface of a silver nanoparticle in 30 ns while the benzyl radical abstracts atomic hydrogen from water in 130 ns to form toluene.
- Published
- 2003
48. Magnetically-actuated blood filter unit attachable to pre-made biochips
- Author
-
Jong-Heon Yang, Kwang Hyo Chung, Chan Woo Park, Chil Seong Ah, Yo Han Choi, Gun Yong Sung, and Wan-Joong Kim
- Subjects
Materials science ,Biomedical Engineering ,Bioengineering ,General Chemistry ,Filter (signal processing) ,Equipment Design ,Microfluidic Analytical Techniques ,Biochemistry ,Magnetics ,Plasma ,High plasma ,Blood plasma ,Humans ,Biochip ,Magnetic actuation ,Filtration ,Whole blood ,Biomedical engineering - Abstract
We present a novel blood filter unit that is designed to separate blood plasma from whole blood by simple magnetic actuation. A non-diluted blood sample is dropped into the filter unit and magnetic attraction is applied to squeeze out only blood plasma while blood particles are filtered by membranes stacked in the filter unit. The new filter device yields good filtering performance with nearly perfect filtering efficiency (∼99.999%), high plasma recovery (∼30%), low blood consumption (
- Published
- 2012
49. Magnetically-actuated blood filter for a CMOS-based nanowire biosensor
- Author
-
Yo Han Choi, Chang-Geun Ahn, Kwang Hyo Chung, Wan-Joong Kim, Jong-Heon Yang, Gun Yong Sung, Chil Seong Ah, and Chan Woo Park
- Subjects
Membrane ,Materials science ,CMOS ,Magnet ,Microfluidics ,Electronic engineering ,Nanowire ,Magnetic separation ,Filter (signal processing) ,Biosensor - Abstract
We present a novel blood filter device which is actuated by simple magnetic squeezing to layered membranes. The filter gives a good performance in high plasma recovery yield (∼25%), nearly-perfect filtering efficiency (∼100%), low blood consumption (
- Published
- 2011
50. Toxin detection by Si photosensitive biosensors with a new measurement scheme
- Author
-
Chang-Geun Ahn, Gun Yong Sung, Jong-Heon Yang, Chil Seong Ah, Kwang Hyo Chung, Wan-Joong Kim, Chan Woo Park, and Yo Han Choi
- Subjects
Silicon ,Materials science ,Aflatoxin B1 ,Opacity ,Biomedical Engineering ,Biophysics ,Analytical chemistry ,Metal Nanoparticles ,Integrated circuit ,Biosensing Techniques ,law.invention ,law ,Electrochemistry ,Immunoassay ,business.industry ,Open-circuit voltage ,Antibodies, Monoclonal ,General Medicine ,Electrochemical Techniques ,Photochemical Processes ,Ray ,Photodiode ,Light intensity ,Microscopy, Electron, Scanning ,Optoelectronics ,Field-effect transistor ,Gold ,business ,Biosensor ,Antibodies, Immobilized ,Biotechnology - Abstract
We propose a new type of photosensitive biosensor with a CMOS compatible Si photodiode integrated circuit, for the high-sensitive detection of small mycotoxin molecules requiring competitive assay approach. In this work, a photodiode is connected to the gate of a field effect transistor (FET) so that the open circuit voltage ( V OC ) of the illuminated photodiode is transferred into the drain/source current ( I DS ) of the FET. The sensing scheme employs competitive binding of toxin molecules (within the sample solution) and toxin–BSA conjugates (immobilized on the photodiode surface) with Au-nanoparticle-labeled antibodies, followed by silver enhancement to generate opaque structures on the photodiode surface. By utilizing the non-linear dependence of the V OC on the light intensity, we can maintain a sufficiently high signal resolution at low toxin concentrations (with most of the incident light blocked) for the competitive assay. By monitoring the I DS of the FET whose gate is driven by the V OC , quantitative detection of Aflatoxin B1 has been achieved in the range of 0–15 ppb.
- Published
- 2011
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