• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.1-6
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• 2019

Organic dye-doped silica nanoparticles are used as a promising nanomaterials for bio-labeling, bio-imaging and bio-sensing. Fluorescent silica nanoparticles(NPs) have been synthesized by the modified $St{\ddot{o}}ber$ method. In this study, dye-free fluorescent silica NPs of various sized were synthesized by Sol-Gel process as the modified $St{\ddot{o}}ber$ method. The functional material of APTES((3-aminopropyl)triethoxysilane) was added as an additive during the Sol-Gel process. The as-synthesized silica NPs were calcined at $400^{\circ}C$ for 2 hours. The surface morphology and particle size of the as-synthesized silica NPs were characterized by field-emission scanning electron microscopy. The fluorescent characteristics of the as-synthesized silica NPs was confirmed by UV lamp irradiation of 365 nm wavelength. The photoluminescence (PL) of the as-synthesized silica NPs with different size was analyzed by fluorometry. As the results, the as-synthesized silica NPs exhibits same blue fluorescent characteristics for different NPs size. Especially, as increased of the silica NPs size, the intensity of PL was decreased. The blue fluorescence of dye-free silica NPs was attributed to linkage of $NH_2$ groups of the APTES layer and oxygen-related defects in the silica matrix skeleton.

• Korean Chemical Engineering Research
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• v.60 no.1
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• pp.1-6
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• 2022

As the demand for wearable devices increases, many studies have been studied on the development of flexible electrode materials recently. In particular, the development of high-performance flexible electrode materials is very important for wearable sensors for healthcare because it is necessary to continuously monitor and accurately detect body information such as body temperature, heart rate, blood glucose, and oxygen concentration in real time. In this study, we fabricated the nonenzymatic glucose sensor based on polyaniline/carbon nanotube fiber (PANI/CNT fiber) electrode. PANI layer was synthesized on the flexible CNT fiber electrode through electrochemical polymerization process in order to improve the performance of a flexible CNT fiber based electrode material. Surface morphology of the PANI/CNT fiber electrode was observed by scanning electron microscopy. And its electrochemical characteristics were investigated by chronoamperometry, cyclic voltammetry, electrochemical impedance spectroscopy. Compared to bare CNT fiber electrode, this PANI/CNT fiber electrode exhibited small electron transfer resistance, low peak separation potential and large surface area, resulting in enhanced sensing properties for glucose such as wide linear range (0.024~0.39 and 1.56~50 mM), high sensitivity (52.91 and 2.24 ㎂/mM·cm²), low detection limit (2 μM) and good selectivity. Therefore, it is expected that it will be possible to develop high performance CNT fiber based flexible electrode materials using various nanomaterials.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.5
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• pp.175-182
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• 2022

Rare-earth elements were doped with Mg to enhance the temperature stability of dielectric properties of BaTiO₃ for its application to MLCC (Multi-Layer Ceramic Capacitor). The additives strongly affect both grain growth and densification behaviors during sintering, and hence dielectric properties. The additive effects therefore should be examined in each system with different additives. This study investigated the crystal structure, grain growth and densification behaviors and related variations in dielectric constant with respect to sintering temperature. Dielectric constant appears to be varied with grain size in a temperature range between 1200 and 1300℃, suggesting the importance of grain size control. The temperature dependence of grain size variation was well explained by an established theory correlating the grain growth behavior with grain boundary structure. This accordance provides a basis for sintering technique to control grain growth thus to improve dielectric constant in rare-earth doped BaTiO₃.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.227-234
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• 2022

In this study, the rheological properties of cement paste composites applied with carbon-based nano-materials were experimental analyzed. Flow table and rheological properties, compressive strength were measured in the cement paste using graphene oxide asqueous solution and carbon nanotube aqueous solution. When carbon nano-materials was mixed in an aqueous solution, flow decreased and plastic viscosity and shear stress were increased. In particular, graphene oxide rapidly increased the plastic viscosity and shear stress. In the case of carbon nanotube aqueous solution, when less than 0.2 % was mixed, the increase rate was low compared to graphene oxide. This is because the specific surface area of graphene, which is in the form of a plate, is large. The compressive strength showed a small amount in strength increase when graphene mix, and CNT had a strength about 112 % of OPC. Carbon-based nanomaterials, is considered that CNT are suitable more to be used construction materials. However, extra studies on the surfactant to be used for mixing proportion and dispersion will be needed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.4
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• pp.136-142
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• 2022

The crystal structure, grain growth behavior, and dielectric properties of BaTiO₃ have been studied with the addition of Dy₂O₃. The powders were synthesized at ratios of (100-x)BaTiO₃-xDy₂O₃ (mol%, x = 0, 0.5, 1.0, 2.0) by a conventional solid-state synthesis, and the powder compacts were sintered at 1250℃ for 2 hours in air. As the amount of added Dy₂O₃ was increased, the crystal structure of the sintered samples changed from a tetragonal to a pseudo-cubic structure, and the tetragonality decreased. In addition, a secondary phase of Ba₁₂Dy_4.67Ti₈O₃₅ appeared when Dy₂O₃ was added. The average grain size after sintering decreased and abnormal grains appeared as the amount of Dy₂O₃ increased. It can be explained that the grain growth behavior of the Dy₂O₃ added-BaTiO₃ occurs due to the two-dimensional nucleation and growth, and is governed by the interface reaction. Further, the correlation between crystal structure, microstructure, and dielectric properties was discussed.

• Economic and Environmental Geology
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• v.55 no.6
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• pp.661-669
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• 2022

The need for miniaturization, high efficiency, and green energy resources as an energy storage device through the development of various electronic device has emerged. Accordingly, nanomaterials with excellent electrochemical properties, such as graphene and graphene hybrids, are attracting attention as promising materials. In particular, in the electric vehicle industry, cost reduction of secondary batteries is a key factor that can determine the spread of related industries, and it is most important to analyze R&D trends for battery material technology and respond to future technological development directions. Therefore, in this study, we tried to suggest a direction for R&D activities in the future by analyzing patent trends for graphene anode material technology for secondary batteries and deriving implications. As a result, in the case of anode material technology, the proportion of foreigners in the US and European patent markets was higher than in the Korean and Japanese patent markets, which means that the US and European marketability is high. In addition, Japanese applicants are filing high-level applications not only in the Japanese patent market but also in other countries suggests that Japan is leading the technology in this field. Lastly, the proportion of research institutes in the patent market of Korea and the US remains high compared to that of Japan and Europe, indicating that the commercialization of technology is still slow in those countries. Therefore research institutes and companies in Korea will have to establish their own strategies for developing and securing materials using the results of patent trends in major countries and major companies analyzed in this study.

• Journal of Industrial Convergence
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• v.21 no.3
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• pp.189-194
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• 2023

Recently, various studies on flexible electronic devices have been performed. In this study, the potential of Ag nanowires was evaluated as a material to replace the ITO transparent conductive film. Ag nanomaterials were formed on the glass by a novel brush coating method and an argon plasma evaporation method based on atmospheric pressure plasma. First, the Ag solution is coated on the glass with a brush, and the remaining solvent is removed with atmospheric plasma. During this process of solvent evaporation, a sound is generated by the reaction between the atmospheric plasma and the solvent. Therefore, the remaining amount of the solvent can be confirmed. In order to observe optical properties and electrical results such as reflectance, transmittance, and absorbance according to the number of coatings of the film, the results were analyzed by coating up to 5 times. For the purpose of investigating the interaction of light with Ag nanowires, reflectance and transmittance were measured while changing the wavelength of light from 200 nm to 800 nm. In the case of absorbance, the trend of increasing light absorption of the Ag nanowires according to the coating was clearly confirmed. The electrical properties showed a great change from the time of coating more than 4 times, and in particular, the resistance value was lower than kΩ/cm2 when the coating was applied 5 times. Based on these optical and electrical results, we plan to verify the possibility of a transparent conductive film by applying it to electronic devices in the future.

• Smart Media Journal
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• v.12 no.5
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• pp.36-45
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• 2023

Recently, in digital agriculture, the types and utilization of greenhouses based on IoT are spreading, and greenhouses are being modernized, enlarged, and even factoryized using smart technology. However, a specific standardization plan has not been proposed according to the equipment for data collection in the smart greenhouse and the size or shape of the greenhouse. In other words, there is a lack of standard data for facility equipment, such as the type and number of sensors and equipment according to the size of the greenhouse, the type of greenhouse construction film and materials suitable for crops and carbon neutrality. Therefore, in this study, the suitability of the implementation, installation and quantity of IoT equipment for data collection was tested, and some standard technologies were presented through the implementation of data collection and communication methods. In addition, impact strength, tensile, tear, elongation, light transmittance, and lifespan issues for PE, PVC, and EVA, which account for about 90% of existing greenhouses, were presented, and the shape, size, and environmental problems of greenhouses made of films were presented. presented in the text. In this research paper, a standardized carbon-neutral modular smart greenhouse using nano-material film was implemented as a solution to environmental problems such as greenhouse size, farm crop type, greenhouse lifespan, and film, and its performance with existing greenhouses was analyzed and presented. Through this, we propose a modularized greenhouse that can be expanded or reduced freely without distinction in the size of the greenhouse or the shape of farmhouse crops, and the lifespan is extended and standardized. Finally, the average characteristics of greenhouses using existing PE, PVC, and EVA films and the characteristics of greenhouses using new carbon-neutral nanomaterials are compared and reviewed, and a plan to implement an expandable IoT greenhouse that supports carbon neutrality is proposed.

• Restorative Dentistry and Endodontics
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• v.45 no.4
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• pp.54.1-54.16
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• 2020

Objectives: This study aimed to synthesize nanocrystals (NCs) of zinc oxide (ZnO) and calcium ion (Ca²⁺)-doped ZnO with different percentages of calcium oxide (CaO), to evaluate cytotoxicity and to assess the effects of the most promising NCs on cytotoxicity depending on lipopolysaccharide (LPS) stimulation. Materials and Methods: Nanomaterials were synthesized (ZnO and ZnO:xCa, x = 0.7; 1.0; 5.0; 9.0) and characterized using X-ray diffractometry, scanning electron microscopy, and methylene blue degradation. SAOS-2 and RAW 264.7 were treated with NCs, and evaluated for viability using the MTT assay. NCs with lower cytotoxicity were maintained in contact with LPS-stimulated (+LPS) and nonstimulated (-LPS) human dental pulp cells (hDPCs). Cell viability, nitric oxide (NO), and reactive oxygen species (ROS) production were evaluated. Cells kept in culture medium or LPS served as negative and positive controls, respectively. One-way analysis of variance and the Dunnett test (α = 0.05) were used for statistical testing. Results: ZnO:0.7Ca and ZnO:1.0Ca at 10 ㎍/mL were not cytotoxic to SAOS-2 and RAW 264.7. +LPS and -LPS hDPCs treated with ZnO, ZnO:0.7Ca, and ZnO:1.0Ca presented similar NO production to negative control (p > 0.05) and lower production compared to positive control (p < 0.05). All NCs showed reduced ROS production compared with the positive control group both in +LPS and -LPS cells (p < 0.05). Conclusions: NCs were successfully synthesized. ZnO, ZnO:0.7Ca and ZnO:1.0Ca presented the highest percentages of cell viability, decreased ROS and NO production in +LPS cells, and maintenance of NO production at basal levels.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.2
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• pp.1-12
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• 2023

In the current era of the global mobile smart device revolution, electronic devices are required in all spaces that people interact with. The establishment of the internet of things (IoT) among smart devices has been recognized as a crucial objective to advance towards creating a comfortable and sustainable future society. In-mold electronic (IME) processes have gained significant industrial significance due to their ability to utilize conventional high-volume methods, which involve printing functional inks on 2D substrates, thermoforming them into 3D shapes, and injection-molded, manufacturing low-cost, lightweight, and functional components or devices. In this article, we provide an overview of IME and its latest advances in application. We review biomimetic nanomaterials for constructing self-supporting biosensor electronic materials on the body, energy storage devices, self-powered devices, and bio-monitoring technology from the perspective of in-mold electronic devices. We anticipate that IME device technology will play a critical role in establishing a human-machine interface (HMI) by converging with the rapidly growing flexible printed electronics technology, which is an integral component of the fourth industrial revolution.