119 results on '"Seungho Cho"'
Search Results
2. The Relationship between Trading Types and Total Volatility in the Korean Stock Market
- Author
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Seungho Cho and Yoo Shiyong
- Published
- 2023
3. Silver Sulfide Nanocrystals as a Biocompatible and Full-Spectrum Photocatalyst for Efficient Light-Driven Polymerization under Aqueous and Ambient Conditions
- Author
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Changhoon Yu, Jaejung Song, Tae In Kim, Yungyeong Lee, Yonghwan Kwon, Jongkyoung Kim, Jeehun Park, Jinho Choi, Junsang Doh, Seung Kyu Min, Seungho Cho, and Min Sang Kwon
- Subjects
General Chemistry ,Catalysis - Published
- 2022
4. High-Performance Electrochemical and Photoelectrochemical Water Splitting at Neutral pH by Ir Nanocluster-Anchored CoFe-Layered Double Hydroxide Nanosheets
- Author
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Je Min Yu, Jaejung Song, Young Kyeong Kim, Jiyeon Oh, Kwang Young Kim, Woo Yeong Noh, Woo Jin Byun, Jin Uk Lee, Changduk Yang, Ji-Wook Jang, Jae Sung Lee, and Seungho Cho
- Subjects
Mechanical Engineering ,General Materials Science ,Bioengineering ,General Chemistry ,Condensed Matter Physics - Published
- 2023
5. High Throughput Image Analytics Using Hough Transformation for Wheat Phenotyping
- Author
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James Y. Kim, Myung-Na Shin, Ji-Hyun Lee, Weon-Tai Jeon, and Seungho Cho
- Subjects
General Engineering - Abstract
HighlightsRGB-based vegetation and leaf area indexes using a smartphone camera.Geo-rectification of skewed images via row detection using Hough Transformation.Open-source software to automate the image stitching and plot-level phenotypic metrics extraction. Abstract. An agricultural field is not always accessible for plant phenotyping with existing mobile platforms due to the limited space and regulated aviation area. Smartphone-triggered ground images were collected on a wheat field that has a limited access to monitor growth conditions of four wheat varieties: Shinyoung (SY), Joseong (JS), Taewoo (TW), and Cheongwoo (CW). For field mapping during the growing season, six sets of the raw images were acquired by a smartphone in an oblique view angle and processed to transform into nadir view images. Algorithms were developed to process the raw tile images for geometric rectification via row detection using Hough Transformation. Stitching software was developed to automate the high throughput image analytics of the skewed tile images into a stitched field image through deskewing, row alignment, overlap trimming, and resizing. Plot-level metrics were extracted to analyze plant growth of the wheat varieties using a gridding method for vegetation and leaf area indexes. The processed images resulted in the successful transformation and consistency of algorithms on image alignment and stitching. Plot-level analysis indicated that SY variety performed superior to the other varieties in both vegetation and leaf area indexes and was significantly different in the canopy coverage from the least performed TW variety. The image analytic methods developed in the study offer a flexible solution to stitch and align tile images by a hand-held camera in both oblique and nadir view via user-friendly interface software for high through plant phenotyping and can be adapted to other stationary or mobile imaging platforms in greenhouse and fields. Keywords: Calibration, Image processing, Phenotyping, Python, Software, Stitching.
- Published
- 2022
6. Analysis of genetic diversity and population structure among cultivated potato clones from Korea and global breeding programs
- Author
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Kwang Ryong, Jo, Seungho, Cho, Ji-Hong, Cho, Hyun-Jin, Park, Jang-Gyu, Choi, Young-Eun, Park, and Kwang-Soo, Cho
- Subjects
Tetraploidy ,Plant Breeding ,Multidisciplinary ,Genotype ,Genetic Variation ,Polymorphism, Single Nucleotide ,United States ,Clone Cells ,Solanum tuberosum - Abstract
Characterizing the genetic diversity and population structure of breeding materials is essential for breeding to improve crop plants. The potato is an important non-cereal food crop worldwide, but breeding potatoes remains challenging owing to their auto-tetraploidy and highly heterozygous genome. We evaluated the genetic structure of a 110-line Korean potato germplasm using the SolCAP 8303 single nucleotide polymorphism (SNP) Infinium array and compared it with potato clones from other countries to understand the genetic landscape of cultivated potatoes. Following the tetraploid model, we conducted population structure analysis, revealing three subpopulations represented by two Korean potato groups and one separate foreign potato group within 110 lines. When analyzing 393 global potato clones, country/region-specific genetic patterns were revealed. The Korean potato clones exhibited higher heterozygosity than those from Japan, the United States, and other potato landraces. We also employed integrated extended haplotype homozygosity (iHS) and cross-population extended haplotype homozygosity (XP-EHH) to identify selection signatures spanning candidate genes associated with biotic and abiotic stress tolerance. Based on the informativeness of SNPs for dosage genotyping calls, 10 highly informative SNPs discriminating all 393 potatoes were identified. Our results could help understanding a potato breeding history that reflects regional adaptations and distinct market demands.
- Published
- 2022
7. Size-Dependent Photovoltaic Performance of CdSe Supraquantum Dot/Polymer Hybrid Solar Cells: 'Goldilocks Problem' Resolved by Tuning the Band Alignment Using Surface Ligands
- Author
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Hyunmi Doh, Juwon Park, Sungjee Kim, Kilwon Cho, Jiwon Bang, Soo Won Heo, Seungho Cho, and Ji Hwang Lee
- Subjects
chemistry.chemical_classification ,Surface (mathematics) ,Materials science ,business.industry ,Size dependent ,Photovoltaic system ,Polymer ,Hybrid solar cell ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,Colloid ,General Energy ,chemistry ,law ,Goldilocks principle ,Solar cell ,Optoelectronics ,Physical and Theoretical Chemistry ,business - Abstract
This study explored the size dependence of colloidal CdSe nanocrystals (NCs) on the photovoltaic properties of CdSe NC/poly(3-hexylthiophene) (P3HT) hybrid bulk-heterojunction (BHJ) solar cell devi...
- Published
- 2020
8. High-performance and stable photoelectrochemical water splitting cell with organic-photoactive-layer-based photoanode
- Author
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Changduk Yang, Ji-Wook Jang, Yongseon Kim, Seungho Cho, Jungho Lee, Sang Myeon Lee, Je Min Yu, Ja Hun Kwak, Jiyeon Oh, Mingyu Jeong, Yoon Seo Kim, and Jaejung Song
- Subjects
Materials science ,Passivation ,Science ,General Physics and Astronomy ,02 engineering and technology ,engineering.material ,010402 general chemistry ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Article ,Solar fuels ,Photoactive layer ,Photocatalysis ,lcsh:Science ,Photocurrent ,Multidisciplinary ,Energy conversion efficiency ,Layered double hydroxides ,General Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Organic semiconductor ,Chemical engineering ,engineering ,Reversible hydrogen electrode ,Water splitting ,lcsh:Q ,0210 nano-technology ,Electrocatalysis - Abstract
Considering their superior charge-transfer characteristics, easy tenability of energy levels, and low production cost, organic semiconductors are ideal for photoelectrochemical (PEC) hydrogen production. However, organic-semiconductor-based photoelectrodes have not been extensively explored for PEC water-splitting because of their low stability in water. Herein, we report high-performance and stable organic-semiconductors photoanodes consisting of p-type polymers and n-type non-fullerene materials, which is passivated using nickel foils, GaIn eutectic, and layered double hydroxides as model materials. We achieve a photocurrent density of 15.1 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE) with an onset potential of 0.55 V vs. RHE and a record high half-cell solar-to-hydrogen conversion efficiency of 4.33% under AM 1.5 G solar simulated light. After conducting the stability test at 1.3 V vs. RHE for 10 h, 90% of the initial photocurrent density are retained, whereas the photoactive layer without passivation lost its activity within a few minutes., While organic semiconductors may be useful in photoelectrochemical water-splitting materials, they show low stability in water. Here, the authors report high-performance and stable organic-semiconductor-based photoanodes passivated using nickel foils, GaIn eutectic, and layered double hydroxides.
- Published
- 2020
9. Smartphone-based High Throughput Phenotyping on Wheat Field
- Author
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James Kim, Myung-Na Shin, Ji-Hyun Lee, Weon-Tai Jeon, and Seungho Cho
- Published
- 2022
10. Measurement of Firm Level Total Factor Productivity of Listed Companies in Korea
- Author
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Shiyong Yoo and Seungho Cho
- Subjects
Business ,Total factor productivity ,Agricultural economics - Published
- 2020
11. Control of structural disorder in spinel ceramics derived from layered double hydroxides
- Author
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Yoon Seok Oh, Jun Han Lee, Il Rok Jeong, Seungho Cho, and Jaejung Song
- Subjects
010302 applied physics ,Materials science ,Process Chemistry and Technology ,Coordination number ,Spinel ,Layered double hydroxides ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Catalysis ,Metal ,Crystallinity ,Chemical engineering ,visual_art ,0103 physical sciences ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,engineering ,Energy transformation ,Ceramic ,0210 nano-technology - Abstract
Spinel oxides are versatile and functional materials with physicochemical properties that are significantly influenced by their structural disorder. The transition from layered double hydroxides (LDHs) to mixed metal oxides (MMOs) containing spinel oxides is a powerful approach to create materials with tailored properties suitable for various applications. Herein, we report the control of structural ordering in spinels related to the crystallinity, cationic inversion, and coordination number of constituent atoms by varying the transformation energy. Transformation from LDHs to spinels with higher applied energy leads to higher crystallinity, lower degree of inversion, and lower ratios of low-coordinated atoms to fully coordinated atoms after treatment with acid. We provide a general framework for controlling structural ordering, that can be applied to other spinels and metal oxides. In addition, LDHs and MMOs possess many chemical and structural degrees of freedom, making it possible to create materials that suit the needs of different applications, such as memory, sensors, catalysis, and energy conversion.
- Published
- 2020
12. Achieving ferromagnetic insulating properties in La0.9Ba0.1MnO3 thin films through nanoengineering
- Author
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Eun-Mi Choi, Seungho Cho, Tuhin Maity, Weiwei Li, Judith L. MacManus-Driscoll, Haiyan Wang, Chao Yun, Rui Wu, Jie Jian, Xing Sun, and Sichuang Xue
- Subjects
Nanocomposite ,Materials science ,Condensed matter physics ,Spintronics ,Doping ,Relaxation (NMR) ,02 engineering and technology ,Nanoengineering ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Ferromagnetism ,General Materials Science ,Multiferroics ,Thin film ,0210 nano-technology - Abstract
Strongly correlated manganites have a wide range of fascinating magnetic and electronic properties, one example being the coexistence of ferromagnetic and insulating properties in lightly-doped bulk. However, it is difficult to translate bulk properties to films. Here, this problem is overcome by thin film nanoengineering of the test case system, La0.9Ba0.1MnO3 (LBMO). This was achieved by using vertically aligned nanocomposite (VAN) thin films of LBMO + CeO2 in which CeO2 nanocolumns form embedded in a LBMO matrix. The CeO2 columns produce uniform tensile straining of the LBMO. Also light Ce doping of intrinsic cation vacancies in the LBMO occurs. Together, these factors strongly reduced the double exchange coupling and metallicity. Hence, while standard plain reference films showed an insulator-to-metal transition at >200 K, originating from defects and complex structural relaxation, the VAN LBMO films exhibited ferromagnetic insulating properties (while maintaining a Tc of 188 K). This is the first time that a combined strain + doping method is used in a VAN system to realise exemplary properties which cannot be realised in plain films. This work represents an important step in engineering high performance spintronic and multiferroic thin film devices.
- Published
- 2020
13. 한국과 중국 소비자의 레스토랑 이용 시 기대불일치가 불평행동에 미치는 영향: 신경증적 경향의 조절효과
- Author
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Seungho Cho and Kim Hyun Jin
- Subjects
Applied psychology ,Business management ,Psychology - Published
- 2019
14. Genetic Characterization of Global Cultivated Potato Clones, Including Korean Potatoes, Using Genome-Wide Single Nucleotide Polymorphism Markers
- Author
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Kwang Ryong Jo, Seungho Cho, Ji-Hong Cho, Hyun-Jin Park, Jang-Gyu Choi, Young-Eun Park, and Kwang-Soo Cho
- Subjects
fungi ,food and beverages - Abstract
Characterizing the genetic diversity and population structure of breeding materials is essential for breeding to improve crop plants. The potato is an important non-cereal food crop worldwide, but breeding potatoes remains challenging owing to their auto-tetraploidy and highly heterozygous genome. We evaluated the genetic structure of a 110-line Korean potato germplasm using the SolCAP 8303 single nucleotide polymorphism (SNP) Infinium array and compared it with potato clones from other countries to understand the genetic landscape of cultivated potatoes. Following the tetraploid model, we conducted population structure analysis, revealing three subpopulations represented by two Korean potato groups and one separate foreign potato group within 110 lines. When analyzing 393 global potato clones, country/region-specific genetic patterns were revealed. The Korean potato clones exhibited higher heterozygosity than those from Japan, the United States, and other potato landraces. We also employed integrated extended haplotype homozygosity (iHS) and cross-population extended haplotype homozygosity (XP-EHH) to identify selection signatures spanning candidate genes associated with biotic and abiotic stress tolerance. Based on the informativeness of SNPs for dosage genotyping calls, 10 highly informative SNPs discriminating all 393 potatoes were identified. Our results could help understanding a potato breeding history that reflects regional adaptations and distinct market demands.
- Published
- 2021
15. Versatile Layered Hydroxide Precursors for Generic Synthesis of Cu‐Based Materials
- Author
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Wonsik Jang, Jihun Kim, Sinmyung Yoon, Miri Kim, Jongkyoung Kim, Kwangjin An, and Seungho Cho
- Subjects
General Medicine - Published
- 2022
16. 한・중 소셜커머스의 서비스 품질이 소비자의 만족과 신뢰도에 미치는 영향: 한국 소셜커머스‘위메프’와 중국‘메이퇀왕’여행상품 중심으로
- Author
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Seungho Cho and Xiaopeng Zou
- Subjects
Focus (computing) ,Service quality ,Business ,Product (category theory) ,Marketing ,China ,Social commerce ,Reliability (statistics) - Published
- 2019
17. Selective, Stable, Bias‐Free, and Efficient Solar Hydrogen Peroxide Production on Inorganic Layered Materials (Adv. Funct. Mater. 25/2022)
- Author
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Jaejung Song, Je Min Yu, Jang Hyuk Ahn, Hyeonjin Cho, Jiyeon Oh, Yoon Seo Kim, Jieun Kim, Myohwa Ko, Seong‐hun Lee, Tae Joo Shin, Hu Young Jeong, Changduk Yang, Jun Hee Lee, Ji‐Wook Jang, and Seungho Cho
- Subjects
Biomaterials ,Electrochemistry ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials - Published
- 2022
18. The Effect of Negative Expectancy Disconfirmation of Restaurant Customers on Complaining Behavior and Switching Intention: Comparative Study in Korea and Japan
- Author
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Seungho Cho
- Subjects
Expectancy theory ,Psychology ,Social psychology - Published
- 2018
19. All-Bismuth-Based Oxide Tandem Cell for Solar Overall Water Splitting
- Author
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Seungho Cho, Yoon Seo Kim, Jae Sung Lee, Jeehye Kim, Jin Hyun Kim, and Aldiar Adishev
- Subjects
Materials science ,Band gap ,Oxide ,Energy Engineering and Power Technology ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Photocathode ,Bismuth ,chemistry.chemical_compound ,symbols.namesake ,Materials Chemistry ,Electrochemistry ,Chemical Engineering (miscellaneous) ,Electrical and Electronic Engineering ,Photocurrent ,business.industry ,Fermi level ,Photoelectrochemical cell ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,symbols ,Optoelectronics ,Water splitting ,0210 nano-technology ,business - Abstract
Photoelectrochemical overall water splitting without an external bias is demonstrated using an all-bismuth-based oxide tandem cell with a CuBi2O4 photocathode and a BiVO4 photoanode. A solution-based nitrate salt decomposition method is developed for preparing a crystalline p-type CuBi2O4 film with a suitable band gap and Fermi level to serve as a photocathode for water splitting. The optimum CuBi2O4 photocathode is prepared by three-layer deposition and heat-treatment at 823 K, which yields the highest photocurrent density of −0.66 mA cm–2 at 0.4 VRHE and reduction onset potential of ≥1.0 VRHE under 1 sun in O2-purged KPi electrolyte. The all-bismuth based oxide tandem cell of Pt/CuBi2O4 photocathode and a cobalt-phosphate (Co-Pi) modified Mo-doped BiVO4 photoanode give a photocurrent density of ∼0.15 mA cm–2 without any applied bias.
- Published
- 2018
20. Selective, Stable, Bias‐Free, and Efficient Solar Hydrogen Peroxide Production on Inorganic Layered Materials
- Author
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Jaejung Song, Je Min Yu, Jang Hyuk Ahn, Hyeonjin Cho, Jiyeon Oh, Yoon Seo Kim, Jieun Kim, Myohwa Ko, Seong‐hun Lee, Tae Joo Shin, Hu Young Jeong, Changduk Yang, Jun Hee Lee, Ji‐Wook Jang, and Seungho Cho
- Subjects
Biomaterials ,Electrochemistry ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials - Published
- 2022
21. A solution-based route to compositionally complex metal oxide structures using high-entropy layered double hydroxides
- Author
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Miri Kim, Inseon Oh, Hyunkyung Choi, Wonsik Jang, Jaejung Song, Chul Sung Kim, Jung-Woo Yoo, and Seungho Cho
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General Energy ,General Engineering ,General Physics and Astronomy ,General Materials Science ,General Chemistry - Published
- 2022
22. Homoepitaxial growth of ZnO nanostructures from bulk ZnO
- Author
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Hyunseok Jang, Seungho Cho, Xiao Kong, Feng Ding, Chao Zhao, and Jaejung Song
- Subjects
Nanostructure ,Materials science ,Nanowire ,New materials ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Nanomaterials ,Characterization (materials science) ,Biomaterials ,Crystal ,Stages of growth ,Colloid and Surface Chemistry ,Facet ,0210 nano-technology - Abstract
Material formation mechanisms and their selective realization must be well understood for the development of new materials for advanced technologies. Since nanomaterials demonstrate higher specific surface energies compared to their corresponding bulk materials, the homoepitaxial growth of nanomaterials on bulk materials is not thermodynamically favorable. We observed the homoepitaxial growth of nanowires with constant outer diameters on bulk materials in two different, solution-based growth systems. We also suggested potential mechanisms of the spontaneous and homoepitaxial growth of the ZnO nanostructures based on the characterization results. The first key factor for favorable growth was the crystal facet stabilization effect of capping agents during the early stages of growth. The second factor was the change in the dominant growth mode during the reaction in a closed system. The spontaneous, homoepitaxial growth of nanomaterials enables the realization of unprecedented, complex, hierarchical, single-crystalline structures required for future technologies.
- Published
- 2020
23. Achieving ferromagnetic insulating properties in La
- Author
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Chao, Yun, Eun-Mi, Choi, Weiwei, Li, Xing, Sun, Tuhin, Maity, Rui, Wu, Jie, Jian, Sichuang, Xue, Seungho, Cho, Haiyan, Wang, and Judith L, MacManus-Driscoll
- Abstract
Strongly correlated manganites have a wide range of fascinating magnetic and electronic properties, one example being the coexistence of ferromagnetic and insulating properties in lightly-doped bulk. However, it is difficult to translate bulk properties to films. Here, this problem is overcome by thin film nanoengineering of the test case system, La
- Published
- 2020
24. Evaluation of the Flexural Performance and CO2 Emissions of the Voided Slab
- Author
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Seungho Cho and Seunguk Na
- Subjects
Materials science ,Structural material ,Article Subject ,020209 energy ,General Engineering ,Anchoring ,02 engineering and technology ,Reinforced concrete ,Compressive strength ,Flexural strength ,Void (composites) ,Ultimate tensile strength ,lcsh:TA401-492 ,0202 electrical engineering, electronic engineering, information engineering ,Slab ,lcsh:Materials of engineering and construction. Mechanics of materials ,General Materials Science ,Composite material - Abstract
Reinforced concrete is regarded as one of the ideal structural materials which comprises concrete with high compressive strength and reinforcing bars with high tensile strength. However, concrete has been pointed out that it consumes a large volume of energy and emits a lot of carbon dioxide during its manufacturing. In order to lower such environmental burdens of concrete structures, a number of studies and approaches have been carried out. The voided slab is also suggested as a new method to reduce the environmental burden since voided section of the slab would use less concrete compared with the normal reinforced concrete slab. However, no studies have evaluated the CO2 emissions and environmental performance of voided slabs. The purpose of this study was to evaluate the structural performance of voided slabs and empirically corroborate their environmental influence. The flexural performance test was carried out based on the variables of the depth of slab, types of the void former materials, and the hollowness ratio. In addition, comparison of the emission of CO2 was also performed by considering the hollowness ratio and types of void former materials over the normal reinforced concrete slab. The structural performance of the voided slab was similar or slightly higher than the normal reinforced concrete slab. The yield strength of specimens was increased approximately 10∼30% over the anticipated yield strength. Based on this result, it is considered that the voided slab would be sufficient to structural performance and beneficial to plane planning in buildings. In general, it is considered that the voided slab would be beneficial to both structural and environmental aspects. However, the test results in this research showed that the voided slab would emit more carbon dioxide emissions compared to the normal reinforced concrete slab. The main source of more CO2 emissions in the voided slab was the anchoring materials. In this research, wires were used to fix the void former materials to the reinforcing bars. In order for the voided slab to become a more eco-friendly and sustainable material, new anchoring methods such as use of recycled materials, new void former materials without anchoring, or other eco-friendly materials should be applied to reduce the emission of CO2.
- Published
- 2018
25. Strongly enhanced dielectric and energy storage properties in lead-free perovskite titanate thin films by alloying
- Author
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Jijie Huang, Yoon Seo Kim, Judith L. MacManus-Driscoll, Xuejing Wang, Wenrui Zhang, Seungho Cho, Han Wang, Chao Yun, Jie Jian, and Haiyan Wang
- Subjects
010302 applied physics ,Materials science ,Renewable Energy, Sustainability and the Environment ,Analytical chemistry ,02 engineering and technology ,Dielectric ,021001 nanoscience & nanotechnology ,01 natural sciences ,Ferroelectricity ,Titanate ,law.invention ,Capacitor ,law ,0103 physical sciences ,Melting point ,Dissipation factor ,General Materials Science ,Electrical and Electronic Engineering ,Thin film ,0210 nano-technology ,Leakage (electronics) - Abstract
Lead-free perovskite oxide thin films prepared by alloying of titanates and materials with lower melting points are shown to have enhanced ferroelectric and dielectric properties. BaTiO3 (or SrTiO3) with 25% addition of BiFeO3 has much improved crystalline perfection because of the lower melting point of the BiFeO3 giving enhanced growth kinetics. The maximum dielectric peak temperature of BaTiO3 is increased by ~ 200 °C and leakage currents are reduced by up to a factor of ~ 100. The loss tangent reduces up to 300 °C, with a factor of > 14 reduction at room temperature. The dielectric breakdown strength is higher by a factor of ~ 3 (> 2200 kV cm−1) and from room temperature up to 500 °C the dielectric constant is > 1000. Also, a low variation of dielectric constant of ~ 9% from room temperature to 330 °C is obtained, compared to ~ 110% for BaTiO3. The maximum polarization (Pmax) is double that of BaTiO3, at 125.3 μC cm−2. The film has high energy storage densities of > 52 J cm−3 at 2050 kV cm−1, matching Pb-based ferroelectric films. The strongly improved performance is important for applications in energy storage and in high temperature (up to 300 °C) capacitors as well as wider application in other electronic and energy technologies.
- Published
- 2018
26. Selective phase transformation of layered double hydroxides into mixed metal oxides for catalytic CO oxidation
- Author
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Sinmyung Yoon, Seungho Cho, Kwangjin An, Jaejung Song, Wonsik Jang, and Jihun Kim
- Subjects
Materials science ,Mixed metal ,Spinel ,General Engineering ,Layered double hydroxides ,General Physics and Astronomy ,General Chemistry ,Crystal structure ,engineering.material ,Redox ,Catalysis ,General Energy ,Adsorption ,Chemical engineering ,Phase (matter) ,engineering ,General Materials Science - Abstract
Summary Phase transformation from layered double hydroxides (LDHs) into mixed metal oxides (MMOs) has been widely used in various catalytic applications owing to its numerous advantages over conventional synthesis methods. Herein we report the results of selective phase transformation of LDHs into spinels and delafossites for the preparation of phase-pure MMO catalysts. Pure cuprous delafossites and cupric spinels were selectively obtained through heat treatment of Cu-based LDHs followed by post-treatments. This enabled the study of the crystalline-phase-dependent CO oxidation activity of the MMO catalysts and their physicochemical properties. The spinel catalysts exhibited higher CO oxidation activities, in comparison with those of the delafossites, with greater redox properties and improved active sites for CO adsorption. Although the crystalline phases were derived from the same LDH precursors, the catalytic properties of the end product were greatly influenced by their crystal structures.
- Published
- 2021
27. A Comparative Study on Consumer Happiness Level in Experienced Consumption and Substance Consumption: Focused on Korean and Chinese Students
- Author
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Seungho Cho
- Subjects
Consumption (economics) ,Substance consumption ,Material consumption ,media_common.quotation_subject ,Happiness ,Social bonding ,Psychology ,Social psychology ,media_common - Published
- 2017
28. Spontaneous stepwise formation of polar-facet-dominant ZnO crystals for enhanced catalytic H2O2 generation
- Author
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Hu Young Jeong, Ji-Eun Kim, Han Beom Jeong, Wonjun Jang, Jong Min Yuk, Hyunseok Jang, Seungho Cho, Jaejung Song, Ji-Wook Jang, and Hyeonjin Cho
- Subjects
Supersaturation ,Materials science ,General Physics and Astronomy ,Nanoparticle ,Crystal growth ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Ascorbic acid ,01 natural sciences ,Specific surface energy ,0104 chemical sciences ,Surfaces, Coatings and Films ,Chemical engineering ,Polar ,Facet ,0210 nano-technology ,Dissolution - Abstract
Noncentrosymmetric polar materials having polar facets exhibit unique and often useful physicochemical properties. However, the fraction of polar facets having a high specific surface energy is, generally, low because of free energy minimization during crystal growth. In this study, a mechanism for the spontaneous formation of polar ZnO crystals with high sphericity and a high fraction of polar ZnO facets, as supported by the results of material characterization, is proposed. Specifically, in a supersaturated solution of l -ascorbic acid, complexes of ZnO and organic species form nanoparticles, which then aggregate and merge to form large spherical structures. In these spherical structures, crystalline domains of polar ZnO oriented along [0001] dominate in the radial direction. In addition, during the growth period, the central part of the structure, which has a high curvature, releases strain by outward mass transfer and dissolution, and the spheres becomes hollow. The resulting hollow spherical particles having a high fraction of polar facets show higher activity for H2O2 generation via O2 reduction than rod-like ZnO structures, which have a dominant nonpolar surface, prepared in the absence of l -ascorbic acid.
- Published
- 2021
29. The Effect of Trust and Authenticity on a Consumer’s Complaining Behavior and Repurchase Intention in a Discount Department Store
- Author
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Seungho Cho
- Subjects
0502 economics and business ,05 social sciences ,050211 marketing ,Business ,050203 business & management - Published
- 2017
30. A Robust Time Series Prediction Model Using POMDP and Data Analysis
- Author
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Seungho Cho, Suho Cho, and Kin Choong Yow
- Subjects
Computer Networks and Communications ,business.industry ,Computer science ,Speech recognition ,Partially observable Markov decision process ,02 engineering and technology ,Machine learning ,computer.software_genre ,Computer Science Applications ,Artificial Intelligence ,020204 information systems ,0202 electrical engineering, electronic engineering, information engineering ,020201 artificial intelligence & image processing ,Artificial intelligence ,Time series ,business ,computer ,Software ,Information Systems - Published
- 2017
31. Heterojunction Area-Controlled Inorganic Nanocrystal Solar Cells Fabricated Using Supra-Quantum Dots
- Author
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Juwon Park, Sungjee Kim, Jiwon Bang, Sungjae Hwang, Seungho Cho, and Sanghwa Jeong
- Subjects
Materials science ,business.industry ,Energy conversion efficiency ,Heterojunction ,02 engineering and technology ,Quantum dot solar cell ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,Nanocrystal ,Quantum dot ,law ,Solar cell ,Optoelectronics ,General Materials Science ,Nanorod ,Self-assembly ,0210 nano-technology ,business - Abstract
A supra-quantum dot (SQD) is a three-dimensional structure formed by the attachment of quantum dots. The SQDs have sizes of tens of nanometer and they maintain the characteristics of the individual quantum dots fairly well. Moreover, their sizes and elemental compositions can be tuned precisely. On the basis of their unique features, in this work, SQDs are used as constituents of the interpenetrating photoactive layers of inorganic nanocrystal p-n heterojunction solar cells to control the p-type and n-type domain sizes (i.e., p-n heterojunction areas) for optimizing the charge-carrier collection. SQD-containing p-n heterojunction solar cells exhibit improved charge transport and thereby higher power conversion efficiency (PCE) (3.03%) owing to their intermediate p-type and n-type domain sizes, which are between those of a bilayer nanorod p-n heterojunction solar cell (PCE: 1.21%) and an interpenetrating nanorod p-n heterojunction solar cell (PCE: 2.40%). This work demonstrates that the self-assembly of nanoscale materials can be utilized for tailoring the spatial distributions of charge carriers, which is beneficial for obtaining an enhanced device performance.
- Published
- 2018
32. Nanoporous Films and Nanostructure Arrays Created by Selective Dissolution of Water-Soluble Materials
- Author
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Haiyan Wang, Hyun-Kon Song, Judith L. MacManus-Driscoll, Xuejing Wang, Chihyun Hwang, Yoon Seo Kim, Jaejung Song, Seungho Cho, Cho, Seungho [0000-0001-7926-5674], and Apollo - University of Cambridge Repository
- Subjects
Nanostructure ,Materials science ,General Chemical Engineering ,General Physics and Astronomy ,Medicine (miscellaneous) ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Biochemistry, Genetics and Molecular Biology (miscellaneous) ,nanocomposites ,General Materials Science ,Thin film ,water‐soluble materials ,Nanocomposite ,Full Paper ,Nanoporous ,nanoporous materials ,Non-blocking I/O ,nanostructure arrays ,General Engineering ,Full Papers ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Amorphous solid ,Chemical engineering ,Physical vapor deposition ,Crystallite ,0210 nano-technology - Abstract
Highly porous thin films and nanostructure arrays are created by a simple process of selective dissolution of a water‐soluble material, Sr3Al2O6. Heteroepitaxial nanocomposite films with self‐separated phases of a target material and Sr3Al2O6 are first prepared by physical vapor deposition. NiO, ZnO, and Ni1− xMgxO are used as the target materials. Only the Sr3Al2O6 phase in each nanocomposite film is selectively dissolved by dipping the film in water for 30 s at room temperature. This gentle and fast method minimizes damage to the remaining target materials and side reactions that can generate impurity phases. The morphologies and dimensions of the pores and nanostructures are controlled by the relative wettability of the separated phases on the growth substrates. The supercapacitor properties of the porous NiO films are enhanced compared to plain NiO films. The method can also be used to prepare porous films or nanostructure arrays of other oxides, metals, chalcogenides, and nitrides, as well as films or nanostructures with single‐crystalline, polycrystalline, or amorphous nature.
- Published
- 2018
33. Formation and Stepwise Self-Assembly of Cadmium Chalcogenide Nanocrystals to Colloidal Supra-Quantum Dots and the Superlattices
- Author
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Hyunmi Doh, Jiwon Bang, Seungho Cho, Sungjee Kim, Bomi Kim, Juwon Park, Sungjae Hwang, and Sanghwa Jeong
- Subjects
Materials science ,Nanostructure ,Chalcogenide ,General Chemical Engineering ,Superlattice ,Dispersity ,Nanotechnology ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Cadmium telluride photovoltaics ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Nanocrystal ,Quantum dot ,Materials Chemistry ,Self-assembly ,0210 nano-technology - Abstract
Nearly monodisperse colloidal superstructures of cadmium chalcogenide quantum dots (QDs) are reported. The superstructures, which we named as supra quantum dot (SQD), are typically composed of hundreds of a-few-nanometer-sized QDs three-dimensionally (3D) assembled by oriented attachment. The synthesis route for SQD is quite universal and can be extended to CdS, CdSe, CdTe, and CdSeTe alloy. The size of SQD can be tuned from tens of nanometers to over a hundred nanometers. In the case of CdSe SQD, zinc-blende seeds (primary QDs) act as the building block for the formation of the 3D assembled structures, SQDs, with discrete intermediates nanostructures. Primary seeds, 4 nm tetrahedral shaped QDs, assembled into a large tetrahedron of 20 nm. The 20 nm tetrahedrons, in turn, self-assembled into a larger tetrahedron of 40 nm. The discrete-in-size and sequential assemblies were followed by conventional growth from the remaining precursors and ripening within the particles to result in spheroidal SQDs. SQDs all...
- Published
- 2016
34. Catalytic materials for efficient electrochemical production of hydrogen peroxide
- Author
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Jaejung Song and Seungho Cho
- Subjects
inorganic chemicals ,Materials science ,Hydrogen ,lcsh:Biotechnology ,chemistry.chemical_element ,02 engineering and technology ,Electrochemistry ,01 natural sciences ,Peroxide ,Redox ,Electrochemical cell ,Catalysis ,chemistry.chemical_compound ,Anthraquinone process ,lcsh:TP248.13-248.65 ,0103 physical sciences ,General Materials Science ,Hydrogen peroxide ,010302 applied physics ,General Engineering ,021001 nanoscience & nanotechnology ,lcsh:QC1-999 ,chemistry ,Chemical engineering ,0210 nano-technology ,lcsh:Physics - Abstract
Hydrogen peroxide (H2O2), the simplest peroxide consisting of only hydrogen and oxygen, is globally used as a green oxidant. It is also a promising fuel source, and it can be produced on large scales in centralized containers. H2O2 is mainly produced by the anthraquinone process, but it involves energy-consuming reactions and generates organic waste. As the demand for H2O2 continues to grow, alternative technologies that overcome these drawbacks are sought for its generation. The generation of H2O2 through the redox reaction of water and oxygen can be a low-cost, sustainable, and efficient production method. However, this reaction requires active and stable catalysts. In general, H2O2 can be generated by the oxidation of H2O at the anode of an electrochemical cell. Alternatively, H2O2 can also be formed by the reduction of O2 at the cathode. Despite the progress in the development and advancement of materials that catalyze these reactions, further research is required to increase the electron transport rates and active sites of the catalyst. In this article, we review the available catalytic materials for the electrochemical production of H2O2 and provide a summary and outlook of this field.
- Published
- 2020
35. Lead-free relaxor thin films with huge energy density and low loss for high temperature applications
- Author
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Seungho Cho, Ahmed Kursumovic, P.J. Curran, D.H.L. Tjhe, Judith L. MacManus-Driscoll, and Weiwei Li
- Subjects
Materials science ,Renewable Energy, Sustainability and the Environment ,business.industry ,02 engineering and technology ,Dielectric ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Energy storage ,0104 chemical sciences ,law.invention ,Crystallinity ,Capacitor ,law ,Optoelectronics ,General Materials Science ,Dielectric loss ,Electrical and Electronic Engineering ,Thin film ,0210 nano-technology ,business ,Leakage (electronics) ,Power density - Abstract
We report record energy storage density (>80 J cm−3) in Pb-free relaxor ferroelectrics based on Mn-doped BiFeO3–BaTiO3 thin films. Rapid interval deposition was used to impose layer-by-layer growth improving crystallinity and lowering unwanted defects concentration. The growth and Mn doping produced an order of magnitude lower leakage, with strongly reduced dielectric loss (from room temperature to >300 °C, and 100 Hz to 1 MHz), e.g. by a factor of 5 at 225 °C and 25 kHz. At room temperature (RT), the dielectric breakdown strength increased by a factor of 1.5 to >3000 kV cm−1 while the dielectric constant remained flat, at ~1000 from RT to 350 °C. The films perform better than competing materials (e.g. PZT and SrTiO3-based) while being Pb-free and while operating up to 350 °C, which SrTiO3-based systems do not. Our work gives considerable promise for high energy and power density capacitors for harsh environments.
- Published
- 2020
36. Design of a Vertical Composite Thin Film System with Ultralow Leakage To Yield Large Converse Magnetoelectric Effect
- Author
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Rui Wu, Seungho Cho, Ahmed Kursumovic, Chao Yun, Xingyao Gao, Haiyan Wang, Judith L. MacManus-Driscoll, Mary E. Vickers, Wu, Rui [0000-0003-2010-5961], Yun, Chao [0000-0002-4027-0510], and Apollo - University of Cambridge Repository
- Subjects
010302 applied physics ,magnetoelectric ,Materials science ,multiferroics ,Magnetism ,business.industry ,Magnetoelectric effect ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Na0.5Bi0.5TiO3 ,01 natural sciences ,Ferroelectricity ,Clamping ,Ferromagnetism ,magnetism ,Electric field ,nanocomposites ,0103 physical sciences ,Optoelectronics ,General Materials Science ,Thin film ,0210 nano-technology ,business ,Leakage (electronics) - Abstract
Electric field control of magnetism is a critical future technology for low-power, ultrahigh density memory. However, despite intensive research efforts, no practical material systems have emerged. Interface-coupled, composite systems containing ferroelectric and ferri-/ferromagnetic elements have been widely explored, but they have a range of problems, for example, substrate clamping, large leakage, and inability to miniaturize. In this work, through careful material selection, design, and nanoengineering, a high-performance room-temperature magnetoelectric system is demonstrated. The clamping problem is overcome by using a vertically aligned nanocomposite structure in which the strain coupling is independent of the substrate. To overcome the leakage problem, three key novel advances are introduced: a low leakage ferroelectric, Na0.5Bi0.5TiO3; ferroelectric–ferrimagnetic vertical interfaces which are not conducting; and current blockage via a rectifying interface between the film and the Nb-doped SrTiO3 substrate. The new multiferroic nanocomposite (Na0.5Bi0.5TiO3–CoFe2O4) thin-film system enables, for the first time, large-scale in situ electric field control of magnetic anisotropy at room temperature in a system applicable for magnetoelectric random access memory, with a magnetoelectric coefficient of 1.25 × 10–9 s m–1.
- Published
- 2018
37. Single-Crystalline Thin Films for Studying Intrinsic Properties of BiFeO3–SrTiO3 Solid Solution Photoelectrodes in Solar Energy Conversion
- Author
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Ady Suwardi, Ji-Wook Jang, Wenrui Zhang, Seungho Cho, Haiyan Wang, Dunwei Wang, and Judith L. MacManus-Driscoll
- Subjects
Materials science ,General Chemical Engineering ,Nanotechnology ,General Chemistry ,7. Clean energy ,Grain size ,Pulsed laser deposition ,Chemical engineering ,Materials Chemistry ,Chemical stability ,Charge carrier ,Thin film ,Layer (electronics) ,Perovskite (structure) ,Solid solution - Abstract
Solid solutions have been widely investigated for solar energy conversion because of the ease to control properties (e.g., band edge positions, charge carrier transport, and chemical stability). In this study, we introduce a new method to investigate intrinsic solar energy conversion properties of solid solutions through fabricating high-quality single-crystalline solid solution films by pulsed laser deposition. This method rules out external factors, such as morphology, crystalline grain size, orientation, density and distribution, surface area, and particle–particle or particle–conducting layer connection, that have plagued previous studies on solid solution photoelectrodes. Perovskite BiFeO3 (BFO) and SrTiO3 (STO) were chosen as “end” members of the solid solutions (i.e., (BFO)x(STO)1–x (0 ≤ x ≤ 1)). Optical and photoelectrochemical (PEC) properties of the solid solutions significantly varied with changing compositions. Among the six studied compositions, BFO:STO (3:1 molar ratio) exhibited the highest...
- Published
- 2015
38. The Reduction of CO2 Emissions by Application of High-Strength Reinforcing Bars to Three Different Structural Systems in South Korea
- Author
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Seungho Cho and Seunguk Na
- Subjects
Engineering ,Input–output model ,020209 energy ,Geography, Planning and Development ,Structural system ,input–output analysis ,high-strength re-bars ,TJ807-830 ,02 engineering and technology ,Management, Monitoring, Policy and Law ,Reuse ,TD194-195 ,Renewable energy sources ,chemistry.chemical_compound ,Material selection ,0202 electrical engineering, electronic engineering, information engineering ,GE1-350 ,Analysis method ,Electrochemical reduction of carbon dioxide ,Waste management ,Environmental effects of industries and plants ,Renewable Energy, Sustainability and the Environment ,business.industry ,Environmental sciences ,rigid-frame structure ,chemistry ,Carbon dioxide ,flat plate system ,quantity of re-bars ,bearing wall system ,Reduction (mathematics) ,business - Abstract
The architecture, engineering, and construction (AEC) industry consume approximately 23% of the national energy annually, and are considered among the highest energy consuming industries. Recently, several studies have focused on establishing strategies to reduce the emissions of carbon dioxide in the AEC industry by utilisation of low-carbon materials, material reuse, recycling and minimal usage; selection of an optimal structural system and structural optimisation; and optimisation of construction operations. While several studies examined material selection and replacement in concrete, there is a paucity of studies investigating the replacement and implementation of high-strength re-bars to lower the carbon dioxide emissions in buildings. To fill this research gap, the purpose of this study involves calculating the emissions of carbon dioxide by applying high-strength reinforcement bars in three different types of buildings. The input–output analysis method was adopted to compute the emissions of carbon dioxide by using the yield strength and size. This study showed that the application of the high-strength re-bars is beneficial in reducing the input amount of materials, although the quantity of reinforcing bars on the development and splice increased. Furthermore, the application of high-strength deformed bars is also advantageous as a means of carbon dioxide reduction in the studied structural systems. In this study, the CO2 emissions of three different structural systems indicated that implementing SD500 re-bars is the most effective method to reduce carbon dioxide emissions.
- Published
- 2017
- Full Text
- View/download PDF
39. Aqueous-Solution Route to Zinc Telluride Films for Application to CO2Reduction
- Author
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Kun-Hong Lee, Youn Jeong Jang, Ganesan Magesh, Jae Young Kim, Seungho Cho, Sungjee Kim, Jae Sung Lee, Won Yong Kim, Jeong Kon Seo, and Ji-Wook Jang
- Subjects
Aqueous solution ,Zinc telluride ,Inorganic chemistry ,Nanowire ,Substrate (chemistry) ,General Medicine ,General Chemistry ,Catalysis ,Photocathode ,Artificial photosynthesis ,chemistry.chemical_compound ,chemistry ,Reagent ,Photocatalysis - Abstract
As a photocathode for CO2 reduction, zinc-blende zinc telluride (ZnTe) was directly formed on a Zn/ZnO nanowire substrate by a simple dissolution-recrystallization mechanism without any surfactant. With the most negative conduction-band edge among p-type semiconductors, this new photocatalyst showed efficient and stable CO formation in photoelectrochemical CO2 reduction at -0.2--0.7 V versus RHE without a sacrificial reagent.
- Published
- 2014
40. Quantum dot–layered double hydroxide composites for near-infrared emitting codes
- Author
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Sungjee Kim, Seong Cheol Hong, and Seungho Cho
- Subjects
Materials science ,Photoluminescence ,Aqueous solution ,Near-infrared spectroscopy ,Composite number ,General Chemistry ,Fluorescence ,chemistry.chemical_compound ,Nanocrystal ,chemistry ,Quantum dot ,Materials Chemistry ,Hydroxide ,Composite material - Abstract
Near-infrared (NIR)-emitting PbS-based quantum dots (QDs) and exfoliated layered double hydroxide (LDH) nanosheets were self-assembled to form photostable composites for NIR-emitting codes. PbS QDs prepared by a pyrolysis synthetic method or PbS–CdS (core–shell) QDs prepared by a cation exchange using PbS QDs were transferred to aqueous solutions by surface ligand exchange to dihydrolipoic acid (DHLA). The DHLA-decorated QDs and exfoliated LDH nanosheets were assembled by electrostatic interactions during vortexing. The QD–LDH composite films prepared by drop-casting exhibit more than 500% higher NIR PL intensities than the counterpart QD films (without LDH matrices) under identical conditions (i.e., QD concentration). Photostability tests under continuous light irradiation reveal that the PbS–CdS QD films are more photostable than the PbS QD films. Formation of the QD–LDH composites gives rise to further enhancement in the photostability of the film. The photostable PbS–CdS QD–LDH composite films were used to create novel NIR-emitting codes. NIR fluorescence images of a pattern of two kinds of PbS–CdS QD–LDH composite films were recorded with an InGaAs CCD camera equipped with optical filters.
- Published
- 2014
41. Large-scale generation of cell-derived nanovesicles
- Author
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Jaesung Park, Ju Jin Kim, J. Yoon, D. Jeong, Yong Song Gho, Yae Jin Yoon, Wonju Jo, Heonyeong Jeong, Seungho Cho, and S. C. Kim
- Subjects
Green Fluorescent Proteins ,Cell ,Nanotechnology ,Biology ,Exosomes ,Mice ,Cytosol ,Drug Delivery Systems ,medicine ,Animals ,General Materials Science ,RNA, Messenger ,Embryonic Stem Cells ,Liposome ,Microscopy, Confocal ,Cell Membrane ,Membrane structure ,RNA ,Microvesicles ,MicroRNAs ,medicine.anatomical_structure ,Membrane protein ,Drug delivery ,NIH 3T3 Cells ,Biophysics ,Nanoparticles ,Intracellular ,Signal Transduction - Abstract
Exosomes are enclosed compartments that are released from cells and that can transport biological contents for the purpose of intercellular communications. Research into exosomes is hindered by their rarity. In this article, we introduce a device that uses centrifugal force and a filter with micro-sized pores to generate a large quantity of cell-derived nanovesicles. The device has a simple polycarbonate structure to hold the filter, and operates in a common centrifuge. Nanovesicles are similar in size and membrane structure to exosomes. Nanovesicles contain intracellular RNAs ranging from microRNA to mRNA, intracellular proteins, and plasma membrane proteins. The quantity of nanovesicles produced using the device is 250 times the quantity of naturally secreted exosomes. Also, the quantity of intracellular contents in nanovesicles is twice that in exosomes. Nanovesicles generated from murine embryonic stem cells can transfer RNAs to target cells. Therefore, this novel device and the nanovesicles that it generates are expected to be used in exosome-related research, and can be applied in various applications such as drug delivery and cell-based therapy.
- Published
- 2014
42. Shear Tests on Voided Slabs with Board-Type Voiding Material
- Author
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Inoh Lee, Jongjin Lim, Seungho Cho, In-Kwan Paik, Taesung Um, and Juyeon Han
- Subjects
Materials science ,Shear (geology) ,Board type ,Composite material - Published
- 2013
43. The reason for an upper limit to the height of spinnable carbon nanotube forests
- Author
-
Teawon Kim, Seungho Cho, Kun-Hong Lee, Jaegeun Lee, Eugene Oh, Hee Jin Kim, Hyejin Kim, Junbeom Park, and Sung-Hyun Lee
- Subjects
Morphology (linguistics) ,Materials science ,Mechanical Engineering ,Nanotechnology ,Carbon nanotube ,Intensity ratio ,law.invention ,symbols.namesake ,Mechanics of Materials ,law ,symbols ,General Materials Science ,Fiber ,Composite material ,Raman spectroscopy - Abstract
The reason for the upper limit on the height of spinnable carbon nanotube (CNT) forests was studied. To analyze the differences between CNT forests with different heights, we synthesized CNT forests using different growth times (3, 6, 9, 12, 15, and 60 min). The height of the CNT forests increased from 260 μm at 3 min to 1.7 mm at 60 min, and the spinnability decreased sharply after 9 min of growth, where a wavy morphology first appeared. Raman analysis of the CNT forest grown for 9 min showed that the intensity ratio of G-band to D-band at the upper region was 1.50 and that near the bottom was 1.14. We also found that the reaction termination process affected the spinnability of the CNT forests. Depending on the termination process, both spinnable and non-spinnable CNT forests could be selectively synthesized, because of the different morphologies in their lower regions. The results suggested that any wavy morphology produced due to a disturbance in growth conditions causes a loss of spinnability.
- Published
- 2013
44. Highly Fluorescent and Stable Quantum Dot-Polymer-Layered Double Hydroxide Composites
- Author
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Yeonggyeong Baek, Sungjee Kim, Jungheon Kwag, Sanghwa Jeong, and Seungho Cho
- Subjects
chemistry.chemical_classification ,Photoluminescence ,Materials science ,General Chemical Engineering ,Composite number ,Quantum yield ,General Chemistry ,Polymer ,Fluorescence ,chemistry.chemical_compound ,chemistry ,Quantum dot ,Materials Chemistry ,Hydroxide ,Composite material ,Luminescence - Abstract
We report a designed strategy for a synthesis of highly luminescent and photostable composites by incorporating quantum dots (QDs) into layered double hydroxide (LDH) matrices without deterioration of a photoluminescence (PL) efficiency of the fluorophores during the entire processes of composite formations. The QDs synthesized in an organic solvent are encapsulated by polymers, poly(maleic acid-alt-octadecene) to transfer them into water without altering the initial surface ligands. The polymer-encapsulated QDs with negative zeta potentials (−29.5 ± 2.2 mV) were electrostatically assembled with positively charged (24.9 ± 0.6 mV) LDH nanosheets to form QD-polymer-LDH composites (PL quantum yield: 74.1%). QD-polymer-LDH composite films are fabricated by a drop-casting of the solution on substrates. The PL properties of the films preserve those of the organic QD solutions. We also demonstrate that the formation of the QD-polymer-LDH composites affords enhanced photostabilities through multiple protections o...
- Published
- 2013
45. Highly Efficient and Stable Cadmium Chalcogenide Quantum Dot/ZnO Nanowires for Photoelectrochemical Hydrogen Generation
- Author
-
Kijung Yong, Seungho Cho, Ji-Wook Jang, Jae Sung Lee, and Minsu Seol
- Subjects
Photocurrent ,Materials science ,Chalcogenide ,General Chemical Engineering ,Inorganic chemistry ,General Chemistry ,Photoelectrochemical cell ,Photochemistry ,Anode ,chemistry.chemical_compound ,chemistry ,Quantum dot ,Electrode ,Materials Chemistry ,Reversible hydrogen electrode ,Hydrogen production - Abstract
Although cadmium chalcogenide quantum dot-sensitized photoanode can utilize the whole visible region of the solar spectrum, its poor photochemical stability owing to hole-induced anodic corrosion remains a major problem for the application in photoelectrochemical hydrogen generation systems. Here, modification with IrOx·nH2O, a well-known water-oxidation catalyst substantially improves the photochemical stability of the quantum dot-sensitized photoanode. Moreover, it induces an increased photocurrent and a cathodic shift of the onset potential. This is the first example that an oxygen-evolution catalyst is employed on a quantum dot-sensitized electrode system, and it shows 13.9 mA cm–2 (at 0.6 V) and −0.277 V vs the reversible hydrogen electrode (RHE), which are the highest photocurrent density and the lowest onset potential attained with a ZnO-based electrode, respectively. An average hydrogen evolution rate of 240 μmol h–1 cm–2 at 0.6 V vs RHE has been achieved on a IrOx·nH2O modified electrode, with al...
- Published
- 2012
46. Anion-Doped Mixed Metal Oxide Nanostructures Derived from Layered Double Hydroxide as Visible Light Photocatalysts
- Author
-
Seungho Cho, Jae Sung Lee, Kun-Hong Lee, Ki-jeong Kong, Eun Sun Kim, and Ji-Wook Jang
- Subjects
Materials science ,Absorption spectroscopy ,Inorganic chemistry ,Doping ,Oxide ,chemistry.chemical_element ,Crystal structure ,Condensed Matter Physics ,Nitrogen ,Electronic, Optical and Magnetic Materials ,Biomaterials ,chemistry.chemical_compound ,chemistry ,Electrochemistry ,Photocatalysis ,Hydroxide ,Visible spectrum - Abstract
Mixed metal oxide (MMO) nanostructures co-doped uniformly by carbon and nitrogen are synthesized for the first time by annealing a terephthalate-intercalated layered double hydroxide (LDH) under ammonia gas flow. The interlayer gallery of LDH allows effective access of NH3 and the carbon source to its crystal lattice for a uniform nitrogen and carbon doping. Such co-doped MMO exhibit significantly red-shifted absorption spectra to visible light region relative to pure MMO. Photoelectrochemical water oxidation and incident-photon-to-current-conversion efficiency of LDH-derived photocatalysts demonstrate that all the visible light absorption caused by the anion doping contributes to the photocatalytic activity over the entire absorbed wavelength range of
- Published
- 2012
47. Self-Assembled Gold Nanoparticle–Mixed Metal Oxide Nanocomposites for Self-Sensitized Dye Degradation under Visible Light Irradiation
- Author
-
Seungho Cho, Jae Sung Lee, Sekyu Hwang, Ji-Wook Jang, and Sungjee Kim
- Subjects
Nanocomposite ,Aqueous solution ,Materials science ,Inorganic chemistry ,Oxide ,Layered double hydroxides ,Nanoparticle ,Surfaces and Interfaces ,engineering.material ,Condensed Matter Physics ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Dynamic light scattering ,Electrochemistry ,engineering ,Zeta potential ,General Materials Science ,Spectroscopy ,Visible spectrum - Abstract
Gold nanoparticle (Au NP)-mixed metal oxide (MMO) nanocomposite photocatalysts for efficient self-sensitized dye degradations under visible light were prepared by an electrostatically driven self-assembly. Dihydrolipoic acid (DHLA)-capped Au NPs (building block I) were synthesized through a room temperature reaction. Their hydrodynamic size was determined as being around 4.9 nm by dynamic light scattering measurements. MMO nanoplates with lateral dimensions of 100-250 nm (building block II) were prepared by a calcination of zinc aluminum layered double hydroxides at 750 °C for 2 h in air. In a pH 7.0 aqueous solution, the DHLA-capped Au NPs had a negative zeta potential (-22 ± 3 mV); on the other hand, the MMO nanoplates had a positive zeta potential (15 ± 2 mV). Electrostatic self-assembly was achieved by stirring an aqueous solution (pH 7.0) containing DHLA-capped Au NPs and MMO nanoplates at room temperature for 1 h. The self-assembled and sequentially calcined nanocomposites exhibited the superior self-sensitized dye degradation efficiency under visible light to that of ZnO, TiO(2) (P25), or pure MMO nanoplates. The enhanced degradation efficiency could be attributed to strong coupling interactions of ZnO and ZnAl(2)O(4) phases of the MMO and the role of Au as an electron sink and mediator for formations of reactive oxidation species and as a light concentrator.
- Published
- 2012
48. Self-assembled oxide films with tailored nanoscale ionic and electronic channels for controlled resistive switching
- Author
-
Seungho, Cho, Chao, Yun, Stefan, Tappertzhofen, Ahmed, Kursumovic, Shinbuhm, Lee, Ping, Lu, Quanxi, Jia, Meng, Fan, Jie, Jian, Haiyan, Wang, Stephan, Hofmann, Judith L, MacManus-Driscoll, Wang, Haiyan [0000-0002-7397-1209], Hofmann, Stephan [0000-0001-6375-1459], and Apollo - University of Cambridge Repository
- Subjects
0306 Physical Chemistry (incl. Structural) ,Science ,0204 Condensed Matter Physics ,Bioengineering ,0912 Materials Engineering ,Article - Abstract
Resistive switches are non-volatile memory cells based on nano-ionic redox processes that offer energy efficient device architectures and open pathways to neuromorphics and cognitive computing. However, channel formation typically requires an irreversible, not well controlled electroforming process, giving difficulty to independently control ionic and electronic properties. The device performance is also limited by the incomplete understanding of the underlying mechanisms. Here, we report a novel memristive model material system based on self-assembled Sm-doped CeO2 and SrTiO3 films that allow the separate tailoring of nanoscale ionic and electronic channels at high density (∼1012 inch−2). We systematically show that these devices allow precise engineering of the resistance states, thus enabling large on–off ratios and high reproducibility. The tunable structure presents an ideal platform to explore ionic and electronic mechanisms and we expect a wide potential impact also on other nascent technologies, ranging from ionic gating to micro-solid oxide fuel cells and neuromorphics., Metal oxide resistive switches rely on the migration of oxygen vacancies and electrons under applied voltage. Here, Cho et al. use nanocomposites to control the electronic and ionic conductivities in spatially distinct channels, and fabricate memristors with high on/off ratios and reproducibility.
- Published
- 2016
49. Photoelectrochemical water splitting strongly enhanced in fast-grown ZnO nanotree and nanocluster structures
- Author
-
Judith L. MacManus-Driscoll, Dongdong Li, Liyi Shi, Abhijeet Sangle, Shuai Yuan, Seungho Cho, Xin Ren, Yin Zhao, Siyuan Zhang, Robert L. Z. Hoye, Sangle, Abhijeet [0000-0003-0848-4583], Hoye, Robert [0000-0002-7675-0065], and Apollo - University of Cambridge Repository
- Subjects
Photocurrent ,0306 Physical Chemistry (incl. Structural) ,Nanostructure ,Materials science ,Renewable Energy, Sustainability and the Environment ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Hydrothermal circulation ,0104 chemical sciences ,Chemical engineering ,Sputtering ,Water splitting ,General Materials Science ,Nanorod ,0210 nano-technology ,Deposition (law) - Abstract
We demonstrate selective growth of ZnO branched nanostructures: from nanorod clusters (with branches parallel to parent rods) to nanotrees (with branches perpendicular to parent rods). The growth of these structures was realized using a three-step approach: electrodeposition of nanorods (NRs), followed by the sputtering of ZnO seed layers, followed by the growth of branched arms using hydrothermal growth. The density, size and direction of the branches were tailored by tuning the deposition parameters. To our knowledge, this is the first report of control of branch direction. The photoelectrochemical (PEC) performance of the ZnO nanostructures follows the order: nanotrees (NTs) > nanorod clusters (NCs) > parent NRs. The NT structure with the best PEC performance also possesses the shortest fabrication period which had never been reported before. The photocurrent of the NT and NC photoelectrodes is 0.67 and 0.56 mA cm-2 at 1 V vs. Ag/AgCl, respectively, an enhancement of 139% and 100% when compared to the ZnO NR structures. The key reason for the improved performance is shown to be the very large surface-to-volume ratios in the branched nanostructures, which gives rise to enhanced light absorption, improved charge transfer across the nanostructure/electrolyte interfaces to the electrolyte and efficient charge transport within the material.
- Published
- 2016
50. Self Assembled Heteroepitaxial Oxide Nanocomposite for Photoelectrochemical Solar Water Oxidation
- Author
-
Jie Jian, Ji-Wook Jang, Leigang Li, Seungho Cho, Haiyan Wang, and Judith L. MacManus-Driscoll
- Subjects
Photocurrent ,Materials science ,Nanocomposite ,General Chemical Engineering ,Oxide ,Heterojunction ,Nanotechnology ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Epitaxy ,7. Clean energy ,01 natural sciences ,Article ,0104 chemical sciences ,Dielectric spectroscopy ,Solar fuels ,chemistry.chemical_compound ,Photoinduced charge separation ,chemistry ,Chemical engineering ,Materials Chemistry ,Reversible hydrogen electrode ,0210 nano-technology - Abstract
We report on spontaneously phase ordered heteroepitaxial SrTiO3 (STO):ZnFe2O4 (ZFO) nanocomposite films that give rise to strongly enhanced photoelectrochemical solar water oxidation, consistent with enhanced photoinduced charge separation. The STO:ZFO nanocomposite yielded an enhanced photocurrent density of 0.188 mA/cm2 at 1.23 V vs a reversible hydrogen electrode, which was 7.9- and 2.6-fold higher than that of the plain STO film and ZFO film cases under 1-sun illumination, respectively. The photoelectrode also produced stable photocurrent and Faradaic efficiencies of H2 and O2 formation that were more than 90%. Incident-photon-to-current-conversion efficiency measurements, Tauc plots, Mott–Schottky plots, and electrochemical impedance spectroscopy measurements proved that the strongly enhanced photogenerated charge separation resulted from vertically aligned pseudosingle crystalline components, epitaxial heterojunctions, and a staggered band alignment of the components of the nanocomposite films. This study presents a completely new avenue for efficient solar energy conversion applications.
- Published
- 2016
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