• Progress in Superconductivity and Cryogenics
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• v.24 no.2
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• pp.19-22
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• 2022

We studied the effect of substrate-induced strain state on the superconducting transition in GdBa₂Cu₃O_7-x(GdBCO)/La_0.7Sr_0.3MnO₃ (LSMO) bilayers deposited on a LaAlO₃ (LAO) substrate. The stain state of LSMO is controlled by increasing the thickness from 20 nm to 80 nm. Analyses on the extended X-ray absorption fine structure (EXAFS) measurements reveal difference in the direction of MnO₆ octahedral distortion depending on the LSMO thickness, which leads to a difference in anisotropy of magnetization of LSMO layer. The superconducting transitions of our system are strongly correlated with the magnetic anisotropy accompanied by the MnO₆ octahedron distortion in a specific direction. This result suggests the possibility of improving the superconducting transition in the GdBCO/LSMO bilayer system by controlling the degree of competition between superconductivity and ferromagnetism via adjusting strain state in the LSMO layer.

• Journal of the Korean Society of Visualization
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• v.20 no.3
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• pp.10-18
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• 2022

We present an experimental investigation on emulsions created during the impact process between a surfactant-laden droplet and an oil layer on water. By varying the surfactant concentration and the viscosity of oil layer, we created emulsions and visualized them using multi-dimensional high-speed imaging. Our analysis shows that the emulsions are more likely to be unstable and decay within a minute if the impacting droplet contains more surfactant. We also found that there are three mechanisms of generation of emulsions depending on the concentration of surfactant and the viscosity of oil layer; the jet pinch-off, cavity pinch-off, and tearing of oil layer. Jet and cavity pinch-off turned out to be dominant mechanisms for high oil viscosities, while tearing of oil layer is dominant for low oil viscosities. Our result is potentially useful in designing optimal dispersant properties for offshore oil contamination.

• Molecules and Cells
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• v.45 no.9
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• pp.603-609
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• 2022

Cells can communicate in a variety of ways, such as by contacting each other or by secreting certain factors. Recently, extracellular vesicles (EVs) have been proposed to be mediators of cell communication. EVs are small vesicles with a lipid bilayer membrane that are secreted by cells and contain DNA, RNAs, lipids, and proteins. These EVs are secreted from various cell types and can migrate and be internalized by recipient cells that are the same or different than those that secrete them. EVs harboring various components are involved in regulating gene expression in recipient cells. These EVs may also play important roles in the senescence of cells and the accumulation of senescent cells in the body. Studies on the function of EVs in senescent cells and the mechanisms through which nonsenescent and senescent cells communicate through EVs are being actively conducted. Here, we summarize studies suggesting that EVs secreted from senescent cells can promote the senescence of other cells and that EVs secreted from nonsenescent cells can rejuvenate senescent cells. In addition, we discuss the functional components (proteins, RNAs, and other molecules) enclosed in EVs that enter recipient cells.

• Journal of Powder Materials
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• v.29 no.5
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• pp.376-381
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• 2022

Tungsten disulfide (WS₂) nanosheets have attracted considerable attention because of their unique optical and electrical properties. Several methods for fabrication of WS₂ nanosheets have been developed. However, methods for mass production of high-quality WS₂ nanosheets remain challenging. In this study, WS₂ nanosheets were fabricated using mechano-chemical ball milling based on the synergetic effects of chemical intercalation and mechanical exfoliation. The ball-milling time was set as a variable for the optimized fabricating process of WS₂ nanosheets. Under the optimized conditions, the WS₂ nanosheets had lateral sizes of 500-600 nm with either a monolayer or bilayer. They also exhibited high crystallinity in the 2H semiconducting phase. Thus, the proposed method can be applied to the exfoliation of other transition metal dichalcogenides using suitable chemical intercalants. It can also be used with high-performance WS₂-based photodiodes and transistors used in practical semiconductor applications.

• Journal of the Korean Vacuum Society
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• v.6 no.S1
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• pp.70-74
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• 1997

The study of the thickness dependence of the electron energy structure of Fe, Ni, Ti and Zr sublayers in Ni/Ti and Fe/Zr multilayers by using the experimental and computer simulated optical spectroscopy has been performed. A series of Ni/Ti and Fe/Ze multiayered films (MLF) with a bilayer period of 0.5 - 30 nm and constant (Ni/Ti) / different (Fe/Zr) sublayer thickness ratios were prepared by using computer-controlled double-pair target face-to-face sputtering onto a glass substrate at room temperature (RT) Computer simulation of the resulting optical properties of these MLF was carried out by solving of multireflection problem with a matrix method assuming either "sharp" interfaces resulting in rectangular depth profiles of the components or "mixed" (alloy-like) interfaces of variable thickness between pure-metal sublayers. Optical constants of pure bulk metals as well as equiatomic alloy interfaces were employed in these simulations. It was shown that the difference between experimental and simulated optical properties of the investigated MLF increases with decrease in sublayer thickness. This result allows to conclude that the electronic structures of sublayers below 4-5 nm thickness in mlf differ from the corresponding bulk metals.ponding bulk metals.

• Food Science of Animal Resources
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• v.42 no.2
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• pp.197-209
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• 2022

Extracellular vesicles (EVs) are nanosized vesicles secreted from cells into the extracellular environment and are composed of a lipid bilayer that contains cargos with biological activity, such as lipids, proteins, mRNAs, and noncoding microRNAs (miRNAs). Due to their biological activity and their role in cell-to-cell communication, interest in EVs is rapidly increasing. Bovine milk is a food consumed by people of all ages around the world that contains not only a significant amount of nutrients but also EVs. Milk-derived EVs also exhibit biological activity similar to other source-derived EVs, and studies on bovine milk EVs have been conducted in various research fields regarding sufficient milk production. In particular, not only are the effects of milk EVs themselves being studied, but the possibility of using them as drug carriers or biomarkers is also being studied. In this review, the characteristics and cargo of milk EVs are summarized, as well as their uptake and stability, efficacy and biological effects as carriers, and future research directions are presented.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.391-392
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• 2012

Graphene is a perfectly two-dimensional (2D) atomic crystal which consists of sp2 bonded carbon atoms like a honeycomb lattice. With its unique structure, graphene provides outstanding electrical, mechanical, and optical properties, thus enabling wide variety of applications including a strong potential to extend the technology beyond the conventional Si based electronic materials. Currently, the widespread application for electrostatically switchable devices is limited by its characteristic of zero-energy gap and complex process in its synthesis. Several groups have investigated nanoribbon, strained, or nanomeshed graphenes to induce a band gap. Among various techniques to synthesize graphene, chemical vapor deposition (CVD) is suited to make relatively large scale growth of graphene layers. Direct growth of graphene on hexagonal boron nitride (h-BN) using CVD has gained much attention as the atomically smooth surface, relatively small lattice mismatch (~1.7％) of h-BN provides good quality graphene with high mobility. In addition, induced band gap of graphene on h-BN has been demonstrated to a meaningful value about ~0.5 eV.[1] In this paper, we report the synthesis of grpahene / h-BN bilayer in a chemical vapor deposition (CVD) process by controlling the gas flux ratio and deposition rate with temperature. The h-BN (99.99％) substrate, pure Ar as carrier gas, and $CH_4$ are used to grow graphene. The number of graphene layer grown on the h-BN tends to be proportional to growth time and $CH_4$ gas flow rate. Epitaxially grown graphene on h-BN are characterized by scanning electron microscopy, atomic force microscopy, and Raman spectroscopy.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.400.1-400.1
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• 2016

Interfacial engineering approaches as an efficient strategy for improving the power conversion efficiencies (PCEs) of inverted polymer solar cells (iPSCs) has attracted considerable attention. Recently, polymer surface modifiers, such as poly(ethyleneimine) (PEI) and polyethylenimine ethoxylated (PEIE), were introduced to produce low WF electrodes and were reported to have good electron selectivity for inverted polymer solar cells (iPSCs) without an n-type metal oxide layer. To obtain more efficient solar cells, quantum dots (QDs) are used as effective sensitizers across a broad spectral range from visible to near IR. Additionally, they have the ability to efficiently generate multiple excitons from a single photon via a process called carrier multiplication (CM) or multiple exciton generation (MEG). However, in general, it is very difficult to prepare a bilayer structure with an organic layer and a QD interlayer through a solution process, because most solvents can dissolve and destroy the organic layer and QD interlayer. To present a more effective strategy for surpassing the limitations of traditional methods, we studied and fabricated the highly efficient iPSCs with mono-layered QDs as an effective multi-functional layer, to enhance the quantum yield caused by various effects of QDs monolayer. The mono-layered QDs play the multi-functional role as surface modifier, sub-photosensitizer and electron transport layer. Using this effective approach, we achieve the highest conversion efficiency of ~10.3% resulting from improved interfacial properties and efficient charge transfer, which is verified by various analysis tools.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.42 no.4
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• pp.433-440
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• 2016

In this study, a poly (amino acid)s derivative grafted with retinoic acids, which could form self-assemblies in an aqueous solution, was successfully synthesized. The synthesized amphiphilic poly (amino acid)s were controlled with 5, 10, 30 mol% substitution of retinoic acid. Then, the amphiphilic poly (amino acid)s were self-assembled by inter/intra molecular stacking of retinoic acids in an aqueous solution. Also, the increasing the degree of substitution (DS) of retinoic acids decreased the size of self-assembled nanoparticles and induced structural transition to bilayer structure from spherical structure. The retinol was stably encapsulated into a core of self-assembled nanoparticle with 10 mol% of DS. This strategy to prepare the self-assemblies of amphiphilic polyaspartamide will serve to improve the efficiency of targeted delivery for a functional cosmetic with various biological modalities.

• Journal of IKEEE
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• v.20 no.2
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• pp.177-180
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• 2016

The effect of varying thickness of Ag/Ti metal bilayer and annealing time have investigated for controlling self-organized nanoparticles (NPs) on 4H-SiC substrate. In addition, Glass and Si substrate which have different surface energy from SiC were fabricated for analyzing interaction of agglomeration. The results of FE-SEM indicated the different formation behaviors of NPs in various ranges of fabrication condition. The surface energy was measured by using a Contact Angle Analyzer. The formation of network-like NPs was observed on Glass and 4H-SiC, respectively, whereas it was not the case on Si substrates. It has been found that the size of NPs increases with decreasing surface energy, due to particle size-dependent hydrophilic properties of substrates. The different formation behavior was explained by using Young's equation for the contact angles between the metal and different substrates.