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Nano Research 2014年第1期7卷 104-109页

作者： Hui Song Kyubong Jo Bock young jung gun young jung School of Materials Science and Engineering Gwangju Institute of Science and Technology (GIST) Gwangju Republic of Korea Department of Chemistry and Interdisciplinary Program of Integrated Biotechnology Sogang University Seoul Republic of Korea Department of General Dentistry College of Dentistry Yonsei University Seoul Republic of Korea

A vertically aligned anatase TiO2 （A-TiO2） nanotube array has been fabricated by coating a ZnO nanorod （NR） template with a TiO2 precursor solution. After coating, the ZnO NR cores were selectively etched in an acidic environment to form TiO2 nanotubes （NTs）. More specifically, after growing the ZnO NRs via a hydrothermal method, one drop of the TiO2 precursor solution was cast to coat the ZnO NRs, the tops of which were previously covered with chemical capping materials by electrostatic interaction, and then the sample was sintered. Finally, the sample was immersed in an acidic solution resulting in selective etching of the ZnO NR cores. Thus, only TiO2 NTs remained on the substrate. The capping material is effectively used to create a perfect, hexagonal open-ended TiO2 NT array, which interestingly extends onset absorption towards the visible region.

关键词： TiO2 nanotubes chemical capping material ZnO nanorod template laser interferencelithography

A facile synthesis of hierarchical Sn3O4 nanostructures in an acidic aqueous solution and their strong visible- light-driven photocatalytic activity

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Nano Research 2015年第11期8卷 3553-3561页

作者： Hui Song Su-young Son Seul Ki Kim gun young jung School of Materials Science and Engineering Gwangju Institute of Science and Technology (GIST) Gwangju 500-712 Republic of Korea Carbon Convergence Materials Research Center Institute of Advanced Composite Materials Korea Institute of Science and Technology (KIST) Jeollabuk-do 565-905 Republic of Korea

Hierarchical tin（Ⅲ） oxide, Sn3O4, nanospheres were synthesized via hydrothermal reaction under strongly acidic ambient conditions. The morphology of Sn3O4 varied with decreasing pH. The prickly SnaO4 nanospheres changed into SnaO4 nanospheres covered with single-crystalline nanoplates having a high BET surface area of ca. 55.05 m^2·g^-1 and a band gap of ca. 2.25 eV. Small amounts （0.05 g） of the hierarchical Sn3O4 nanostructures completely decomposed a 30% methyl orange （MO） solution in 100 mL deionized water within 15 min under one sun condition （UV ＋ visible light）. The Sn3O4 photocatalyst exhibited a fast decomposition rate of 1.73 ×10^-1 min^-1, which is a 90.86% enhancement relative to that of the commercially available P25 photocatalyst. The high photocatalytic activity of the hierarchical Sn3O4 nanostructures is attributed to its ability to absorb visible light and its high surface-to-volume ratio.

关键词： Sn3O4 hierarchical structure hydrothermal morphology engineering photocatalyst

Domain-engineered BiFeO3 thin-film photoanodes for highly enhanced ferroelectric solar water splitting

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Nano Research 2018年第2期11卷 642-655页

作者： Jaesun Song Taemin Ludvic Kim Jongmin Lee Sam Yeon Cho Jaeseong Cha Sang Yun Jeong Hyunji An Wan Sik Kim Yen-Sook jung Jiyoon Park gun young jung Dong-Yu Kim Ji young Jo Sang Don Bu Ho Won Jang Sanghan Lee School of Materials Science and Engineering Gwangju Institute of Science and Technology (GIST) Gwangju Republic of Korea Department of Materials Science and Engineering Research Institute of Advanced Materials Seoul National University Seoul Republic of Korea Department of Physics Chonbuk National University Jeonju Republic of Korea

In photoelectrochemical （PEC） water splitting, charge separation and collection by the electric field in the photoactive material are the most important factors for improved conversion efficiency. Hence, ferroelectric oxides, in which electrons are the majority carriers, are considered promising photoanode materials because their high built-in potential, provided by their spontaneous polarization, can signifi＇canfly enhance the separation and drift of photogenerated carriers. In this regard, the PEC properties of BiFeO3 thin-film photoanodes with different crystallographic orientations and consequent ferroelectric domain structures are investigated. As the crystallographic orientation changes from （001）pc via （ll0）pc to （lll）p~, the ferroelastic domains in epitaxial BiFeO3 thin films become mono-variant and the spontaneous polarization levels increase to 110 btC/cm2. Consequent136 the photocurrent density at 0 V vs. Ag/AgC1 increases approximately 5.3-fold and the onset potential decreases by 0.180 V in the downward polarization state. It is further demonstrated that ferroelectric switching in the （lll）pc BiFeO3 thin-film photoanode leads to an approximate change of 8,000% in the photocurrent density and a 0.330 V shift in the onset potential. This study strongly suggests that domain-engineered ferroelectric materials can be used as effective charge separation and collection layers for efficient solar water-splitting photoanodes.

关键词： BiFeO3 ferroelectric photoelectrochemical domain orientation pulsed laser deposition

Charge transfer in graphene/polymer interfaces for CO2 detection

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Nano Research 2018年第7期11卷 3529-3536页

作者： Myungwoo Son Yusin Pak Sang-Soo Chee Francis Malar Auxilia Kihyeun Kim Byung-Kee Lee Sungeun Lee Sun Kil Kang Chaedeok Lee Jeong Soo Lee Ki Kang Kim Yun Hee Jang Byoung Hun Lee gun-young jung Moon-Ho Ham School of Materials Science and Engineering Research Institute for Solar and Sustainable Energies Gwangju Institute of Science & Technology 723 Cheomdangwagi-ro Buk-gu Gwangju 61005 Republic of Korea Materials & Devices Advanced Research Institute LG Electronics Woomyeon R&D Campus 38 Baumoe-ro Seocho-gu Seoul 06763 Republic of Korea Department of Energy and Materials Engineering Dongguk University Seoul 04620 Republic of Korea Energy Systems Engineering Daegu Gyeongbuk Institute of Science & Technology 333 Technojungang-daero Hyeonpung-myeon Dalseong-gun Daegu 42988 Republic of Korea

Understanding charge transfer processes between graphene and functional materials is crucial from the perspectives of fundamental sciences and potential applications, including electronic devices, photonic devices, and sensors. In this study, we present the charge transfer behavior of graphene and amine-rich polyethyleneimine （PEI） upon CO2 exposure, which was significantly improved after introduction of hygroscopic polyethylene glycol （PEG） in humid air. By blending PEI and PEG, the number of protonated amine groups in PEI was remarkably increased in the presence of water molecules, leading to a strong electron doping effect on graphene. The presence of CO2 gas resulted in a large change in the resistance of PEI/PEG-co-functionalized graphene because of the dramatic reduction of said doping effect, reaching a maximum sensitivity of 32% at 5,000 ppm CO2 and an applied bias of 0.1 V in air with 60% relative humidity at room temperature. This charge transfer correlation will facilitate the development of portable graphene-based sensors for real-time gas detection and the extension of the applications of graphene-based electronic and photonic devices.

关键词： graphene polyethyleneimine (PEI) polyethylene glycol carbon dioxide charge transfer

Effects of three consecutive monthly intravitreal injection of ranibizumab for polypoidal choroidal vasculopathy in Korea

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International Journal of Ophthalmology(English edition) 2015年第2期8卷 315-320页

作者： young gun Park Seungbum Kang young jung Roh Department of Ophthalmology College of Medicine The Catholic University of Korea Yeouido St. Mary's Hospital Department of Ophthalmology The Catholic University of Korea Daejeon St. Mary's Hospital

AIM: To evaluate the efficacy and safety of three consecutive monthly injections of intravitreal ranibizumab for the treatment of polypoidal choroidal vasculopathy(PCV) in ***: A retrospective chart review of 25 patients(27 eyes) with PCV was conducted. Patients received three initial monthly intravitreal injections(0.5 mg) of ranibizumab and were monitored monthly for 12 mo from January 2010 to October 2011. Reinjection of ranibizumab after three initial monthly loading was administered on an as-needed basis, guided by the optical coherence tomography(OCT), fluorescein angiography(FA) and indocyanine green angiography(ICGA). The main outcomes were the changes of the mean best corrected Snellen visual acuity(VA), central macular thickness(CMT) by OCT, the changes of polyps and branching vascular network by FA and ICGA, and total number of injections received by patients during the 12 ***: The mean best corrected Snellen visual acuities at baseline, 1, 3, 6 and 12 mo after primary injection were 0.77 ±0.59, 0.76 ±0.53, 0.70 ±0.47, 0.63 ±0.43,0.61 ±0.43, 0.62 ±0.42 log MAR, respectively, and showed significant improvement at 3, 6, 12mo(P =0.003, P =0.002,P =0.018, Wilcoxon signed-rank test). The mean CMT at baseline, 1, 2, 3, 6, and 12 mo was 312.41 ±66.38 μm,244.59 ±71.47 μm, 232.32 ±69.41 μm, 226.69 ±69.03 μm,228.62 ±37.07 μm, 227.59 ±51.01 μm respectively, and showed significant reduction(all P <0.001, Wilcoxon signed-rank test). Polypoidal lesions resolved on ICGA in 3 eyes(11.1%) and a branching vascular network remained in all 24 eyes(88.9%). A total of 106 injections were given in the 12-month period, which equaled to a mean of 3.92(range, 3-6) times. Sixteen of the 27 treatedeyes had additional 1.56 ±0.91 injections. The others(11eyes) had just 3 consecutive ***: An initial loading dose of three monthly ranibizumab injections is a safe and effective method in treating PCV, with visual and anatomical improvement over one ye

关键词： ranibizumab polypoidal choroidal vasculopathy intravitral injection

A Self‑Regenerable Fiber Sloughing Its Heavy Metal Skin for Ultrahigh Separation Capability

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Advanced Fiber Materials 2023年第6期5卷 2127-2142页

作者： youngkyun jung Ji Su Park Kyung‑Won jung young gun Ko Jae‑Woo Choi Center for Water Cycle Research Korea Institute of Science and TechnologySeoul 02792Republic of Korea Center for Bionics Korea Institute of Science and TechnologySeoul 02792Republic of Korea Department of Chemical Engineering and Materials Science Sangmyung UniversitySeoul 03016Republic of Korea Division of Energy&Environment Technology KIST SchoolKorea University of Science and Technology(UST)Seoul 02792Republic of Korea

Developing efficient separation materials for recovering metal resources from aqueous environments is crucial for the sustainable water–food–energy nexus,which addresses the interdependence between energy production,water production,and energy *** material-based separation processes have demonstrated outstanding ***,electric energy and chemicals are used to frequently replace the separation materials used in such processes owing to their short life *** study presents a methodology for designing the self-regenerable fiber(SRF)according to the types of metals through a self-regeneration *** SRF can semi-permanently recover the metal resources from water through a repetitive adsorption–crystallization–detachment process of metal ions on its *** ionic metal resources are adsorbed and crystallized with the counter-anions on the SRF ***,the metal crystals are self-detached from the SRF surface by the collision between the crystals and curvature and non-sticky surface of the ***,a module containing the SRF maintains its metal recovery capability even during continuous injection of the metal solution without its *** findings highlight the significance of interfacial engineering and further guide the rational design of energy/environmentally friendly resource recovery modules.

关键词： Self-regeneration model Self-regenerable fiber Semi-permanent adsorption capability Metal crystal growth-detachment

Advanced prediction of organic–metal interactions through DFT study and electrochemical displacement approach

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Journal of Magnesium and Alloys 2023年第1期11卷 301-316页

作者： Abdelkarim Chaouiki Wail Al Zoubi young gun Ko Materials Electrochemistry Group School of Materials Science and EngineeringYeungnam UniversityGyeongsan 38541South Korea

Heterocyclic compounds are the promising biological compounds as nature-friendly for the corrosion protection of metallic *** this work,three heterocyclic compounds such as 1-azanaphthalene-8-ol(8-AN),2-methylquinoline-8-ol(8-MQ),and 8-quinolinol-5-sulfonic acid(8-QSA)were used as green compounds,and their anti-corrosion performance for AZ31 Mg in saline water was discussed on the basis of impedance interpretation and surface *** found that the electrochemical performance was improved in the order of 8-AN>8-MQ>8-QSA,demonstrating the electron donor effect of N-heterocycles to form coordination complexes on the magnesium *** the electrochemical performance,the protective layer constructed at the optimal concentration reinforces the barrier against aggressive environments,with potential inhibition efficiency of 87.4%,99.0%,and 99.9%for 8-QSA,8-MQ,and 8-AN,*** chemical parameters and electron density distribution for free organic species in the absence and presence of Mg^(2+)cation were evaluated using density functional theory(DFT).Upon the formation of coordination complexes between organic compound and Mg^(2+),energy gap underwent change about ΔE=5.7 eV in the 8-AN/Mg^(2+)***,the adsorption of heterocyclic compounds on Mg surface reveals the formation of strong covalent bonds with Mg atoms,which further confirmed by the electron density difference and projected density of states *** on theoretical calculations,three inhibitors can adsorb on the metal surface in both parallel and perpendicular orientations via C,O and N *** the parallel configuration,the C-Mg,N-Mg and O-Mg bond distances are between 2.11 and 2.25˚A,whereas the distances in the case of perpendicular adsorption are between 2.20 and 2.40˚A(covalent bonds via O and N atoms).The results indicated that parallel configurations are energetically more stable,in which the adsorption energies are-4.48 eV(8-AN),-4.28 eV(8-MQ)and-3.82 e

关键词： Organic layer Heterocyclic compounds Electrochemical behavior DFT modeling

Nucleation and growth behavior of coating film on Mg–Al–Zn alloy with different surface topographies via plasma electrolytic oxidation

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Journal of Magnesium and Alloys 2022年第8期10卷 2185-2192页

作者： Nisa Nashrah Sung Hun Baek young gun Ko Materials Electrochemistry Group School of Materials Science and EngineeringYeungnam UniversityGyeongsan 38541Republic of Korea

This work was made to investigate how nucleation and growth behavior of the coating film were affected by surface topographies of Mg–Al–Zn alloy substrate during the initial stage of plasma electrolytic oxidation(PEO).To satisfy this end,a single substrate was prepared by mechanical treatment exhibiting rough and smooth regions with an equal area on the *** rough region with prominent hills and grooves induced the breakdown of passive film,which was indicated by an early appearance of plasma discharge on the rough region since nucleation of coating film occurred preferentially around the ***,the coating film grown on the grooves was somewhat thicker and more porous than the film grown on the hills and smooth *** was due to the fact that the growth of the coating film was found to be localized in the presence of rough region,which was in line with the discharge ***,the nucleation and growth behavior during the initial stage of PEO will be discussed schematically on the basis of microstructural interpretation.

关键词： Mg alloy Surface roughness Plasma electrolytic oxidation Coating film

Impacts of optimization strategies on performance,power/energy consumption of a GPU based parallel reduction

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Journal of Central South University 2017年第11期24卷 2624-2637页

作者： Phuong Thi Yen Lee Deok-young Lee Jeong-gun Smart Computing Lab. Department of Computer EngineeringHallym UniversityChuncheon 24252Korea College of General Education Hallym UniversityChuncheon 24252Korea

In the era of modern high performance computing, GPUs have been considered an excellent accelerator for general purpose data-intensive parallel applications. To achieve application speedup from GPUs, many of performance-oriented optimization techniques have been proposed. However, in order to satisfy the recent trend of power and energy consumptions, power/energy-aware optimization of GPUs needs to be investigated with detailed analysis in addition to the performance-oriented optimization. In this work, in order to explore the impact of various optimization strategies on GPU performance, power and energy consumptions, we evaluate performance and power/energy consumption of a well-known application running on different commercial GPU devices with the different optimization strategies. In particular, in order to see the more generalized performance and power consumption patterns of GPU based accelerations, our evaluations are performed with three different Nvdia GPU generations(Fermi, Kepler and Maxwell architectures), various core clock frequencies and memory clock frequencies. We analyze how a GPU kernel execution is affected by optimization and what GPU architectural factors have much impact on its performance and power/energy consumption. This paper also categorizes which optimization technique primarily improves which metric(i.e., performance, power or energy efficiency). Furthermore, voltage frequency scaling(VFS) is also applied to examine the effect of changing a clock frequency on these metrics. In general, our work shows that effective GPU optimization strategies can improve the application performance significantly without increasing power and energy consumption.

关键词： parallel reduction GPU code optimization power energy voltage frequency scaling

Fabrication of branch-like Aph@LDH-MgO material through organic-inorganic hybrid conjugation for excellent anti-corrosion performance

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Journal of Magnesium and Alloys 2023年第7期11卷 2469-2485页

作者： Maryam Chafiq Abdelkarim Chaouiki Rachid Salghi young gun Ko Materials Electrochemistry Laboratory School of Materials Science and EngineeringYeungnam UniversityGyeongsan 38541Republic of Korea Laboratory of Applied Chemistry and Environment ENSAUniversity Ibn ZohrPO Box 1136Agadir80000Morocco

Layered double hydroxides(LDH)frameworks have shown significant enhancement in stability and reusability,and their tailorable architecture brings new insight into the development of the next generation of hybrid materials,which attracted considerable attention in many fields over the *** of the factors contributing to the widespread applicability of layered double hydroxides is their adaptable composition,which can accommodate a wide spectrum of potential anionic *** exceptional property makes the LDH system simple to adjust for various ***,most LDH systems are synthesized in situ in an autoclave at high temperatures and pressures that severely restrict the industrial use of such coating *** this study,LDH was directly synthesized on a magnesium alloy that had undergone plasma electrolytic oxidation(PEO)treatment in the presence of ethylenediaminetetraacetic acid,thereby avoiding the use of hydrothermal autoclave *** LDH system was compared with a hybrid architecture consisting of organic-inorganic *** organic layer was fabricated on top of the LDH film using 4-Aminophenol(Aph)compound,resulting in a smart hierarchical structure that can provide a robust Aph@LDH film with excellent anti-corrosion *** the molecular level,the conjugation characteristics and adsorption mechanism of Aph molecule were studied using two levels of theory as ***,Localized orbit locator(LOL)-πisosurface,electrostatic potential(ESP)distribution,and average local ionization energy(ALIE)on the molecular surface were used to highlight localization region,reveal the favorable electrophilic and nucleophilic attacks,and clearly explore the type of interactions that occurred around interesting ***,first-principles based on density functional theory(DFT)was applied to study the hybrid mechanism of Aph on LDH system and elucidate their mutual *** experimental and computational analyses suggest t

关键词： Magnesium alloy Surface modification LDH Organic-inorganic hybrid materials Inter-/intra-molecular interactions