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113 results on '"Son, Yongkeun"'

19. Hazardous acid detection based on chitosan‐grafted‐polyaniline copolymer.

Author

Lee, Sangyong, Choi, Dongchul, and Son, Yongkeun

Subjects
POLYANILINES, CHITOSAN, COPOLYMERS, SCANNING electron microscopy, HYDROCHLORIC acid
Abstract

Polyaniline (PANI) has been utilized very well as an active material for hazardous acid detection device. Because its electrical conductivity is developing when it is doped with the protonic acid. However, a critical disadvantage of this material is its insolubility in general solvents so its processability is very poor. In this work, we prepared a Chitosan‐g‐PANI (Cs‐g‐PANI) copolymer to improve its solubility and prossability using common solvents and use film form of the final product to develop a sensitive device, which responds to the presence of hazardous acids. The synthetic Cs‐g‐PANI showing good solubility and excellent film forming properties was characterized by Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, as well as X‐ray diffraction analysis, and scanning electron microscopy. The physical properties of Cs‐g‐PANI films were optimized by controlling the Cs composition. Constant potential was applied to this material for detecting the existence of hazardous acids such as hydrochloric acid (HCl), nitric acid, formic acid, and acetic acid. Our findings suggest that this device responds to the presence of HCl faster than any other acids. The detection mechanism is discussed in detail. POLYM. ENG. SCI., 59:E105–E110, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Published
2019
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20. Electrochemical Template Synthesis of Conducting Polymer Microstructures at Addressed Positions

Author

Yun Geum-Hee, Suh Su-Jeong, Lee Seung Hyoun, and Son Yongkeun

Subjects
chemistry.chemical_classification, Conductive polymer, chemistry.chemical_compound, Working electrode, Materials science, chemistry, Polymerization, Electrode, Nano, Nanotechnology, Polymer, Electrolyte, Polyvinyl alcohol
Abstract

The nano or micro sized structures of conducting polymer had been prepared by synthesizing the desired polymer within the pores of template of nano or micro porous membrane filter. In this study, we had tried to fabricate conducting polymer microstructures on an electrode by using electrochemical deposition adopting template synthesis. Our attention was focused on two different things, attaching template on the electrode and fabricating microstructures only at limited areas of the electrode. A conducting polymer, PEDiTT (poly 3,4-ethylenedithi-athiophene) solution was blended with PVA(polyvinyl alcohol) solution and used as an conducting adhesive. After attaching template membrane, the electrode were immersed in 0.5M pyrrole in 0.1M KCI solution, and electrochemical polymerization was performed. The growth process of the microstructures studied by SEM. The electrochemical fabrication of conducting polymer was performed by using two-electrode system. A large working electrode and a micro scale disc electrode were used for the confined area synthesis. Polymerization potential was 4V in an electrolytic solution made of KCI in deionized water. The optimum polymerization conditions were, i.e. (4V/100sec) for electrode and (6V/30 sec) for electrode.

Published
2004

22. Solution-processed yolk–shell-shaped WO3/BiVO4 heterojunction photoelectrodes for efficient solar water splitting.

Author

Jin, Bingjun, Jung, Eunji, Ma, Ming, Kim, Sungsoon, Zhang, Kan, Kim, Jin Il, Son, Yongkeun, and Park, Jong Hyeok

Abstract

The WO3/BiVO4 heterojunction is regarded as one of the most promising photoanode materials for photoelectrochemical (PEC) water splitting. To improve the solar water splitting efficiency, maximizing the solar light absorption efficiency in a photoelectrode is still a critical issue. Here, to achieve the aforementioned need, we designed and fabricated a WO3 film consisting of yolk–shell structured nanoparticles via solution processing. A thin BiVO4 layer with a smaller bandgap was coated onto the surface and inside the WO3 shells, providing a rationally designed inner space between the particles and the shell for better electrolyte accessibility. The yolk–shell-shaped PEC photoanode not only induces efficient light absorption but also plays an important role in electron collection from BiVO4 due to an enlarged contact area. The structure–PEC performance relationship was studied by combining ultraviolet-visible (UV-vis) absorption spectroscopy with a specular and diffuse reflectance technique, which illustrates that the yolk–shell morphology has a superior light absorption ability than conventional hollow or dense film structures. The pure yolk–shell (Y-WO3/BiVO4) photoanode possessed a photocurrent density of 2.3 mA cm−2 and achieved a highest value of ∼5.0 mA cm−2 after adding a Fe–Ni co-catalyst at a bias of 1.23 V vs. RHE under AM 1.5 illumination (100 mW cm−2). [ABSTRACT FROM AUTHOR]

Published
2018
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23. Electrosynthesis of Cobalt Telluride Thin Films by Voltammetry Combined with Electrochemical Quartz Crystal Microgravimetry

Author

Jee, Woo, Paeng, Jung, Son, Yongkeun, Jang, Yunhyeok, Rho, Kongshik, and Myung, Noseung

Abstract

Cobalt telluride (CoTe) thin films were electrodeposited for the first time using alkaline solutions containing nitrilotriacetic acid (NTA), CoCl2, and K2TeO3. NTA was employed in order to shift the reduction potential of cobalt in the negative direction and to stabilize Co2+ ions in alkaline electrolytes via the formation of Co-NTA complexes. The electrodeposition mechanism was investigated by linear sweep voltammetry (LSV) combined with electrochemical quartz crystal microgravimetry (EQCM). The formation of CoTe is proposed to occur through the reaction of Co2+ with HTe[?], which is generated by the reduction of TeO32[?] via a 6-electron reduction pathway. A concurrent pathway consists of the stepwise reduction of TeO32[?] to Te by a 4-electron process, followed by the 2-electron process reduction of Te to HTe[?]. The electrodeposited CoTe films were characterized by a variety of physical methods including scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, and X-ray photoelectron spectroscopy. An optical energy bandgap of [?]1.86 eV was obtained by diffuse reflectance spectroscopy.

Published
2019

41. Growth mechanism and photoluminescence properties of controlled PbWO4 micro- and mesocrystals obtained by the surfactant-assisted solvothermal method.

Author

Wang, Wenxiu, Lee, Sangyong, Piao, Hushan, Choi, Dongchul, and Son, Yongkeun

Subjects
PHOTOLUMINESCENCE, CRYSTAL growth, CATIONIC surfactants, CETYLTRIMETHYLAMMONIUM bromide, DEIONIZATION of water
Abstract

In this paper, we report on the ortho-hexaclaval and size-controlled spherical PbWO4 micro- and mesocrystals synthesized by the surfactant-assisted solvothermal method with cationic surfactant cetyltrimethylammonium bromide (CTAB), deionized water or ethylene glycol solvents. The resulting hierarchical PbWO4 crystals were characterized by X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy and selected area electron diffraction. Experimental results indicated that CTAB played a critical role in the formation of specific structures. Finally, the optical properties were investigated at room temperature by means of ultraviolet-visible diffuse reflectance and photoluminescence measurements. [ABSTRACT FROM AUTHOR]

Published
2015
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