• Bulletin of the Korean Chemical Society
• /
• v.25 no.7
• /
• pp.1025-1030
• /
• 2004

A hybrid linear polymer-dendrimer block copolymer, poly(ethylene glycol)-block-poly(L-lysine) dendrimer, was synthesized and introduced to form polyionic complexes with DNA. The copolymer formed core-shell type nanoparticles with plasmid DNA. From dynamic light scattering experiments, the mean diameter of the polyplexes was observed to be 154.4 nm. The complex showed much increased water solubility compared to poly(L-lysine). The plasmid DNA in polyplexes was efficiently protected from the enzymatic digestion of DNase I. The cytotoxicity and transfection efficiency for 293 cells was measured in comparison with poly(Llysine).

• Smart Structures and Systems
• /
• v.25 no.3
• /
• pp.337-343
• /
• 2020

In this paper, we focused on the self-healing concrete using new nano-capsules. Three types of nano-capsules with respect to availability, high strength and temperature tolerance are used; type 1 is URF and polyethylene (PE) as shell and nano titanium oxide (TiO₂) as core, type 2 is URF and PE as shell and nano silica oxide (SiO₂) as core, type 3 is PE as shell and nano silica oxide (SiO₂) as core. The concrete samples mixed by nano-capsules with three percents of 0.5, 1 and 1.5. Based on experimental tests and the compressive strength of samples, the URF-PE-SiO₂ is selected for additional tests of compressive strength before and after recovery, ultrasonic test, ion chlorine and water penetration depths. After careful investigation, it is concluded that the optimum value of URF-PE-SiO₂ nano-capsules is 0.5% since leads to higher compressive strength, ultrasonic test, ion chlorine and water penetration depths.

• Transactions of the Korean hydrogen and new energy society
• /
• v.29 no.5
• /
• pp.450-457
• /
• 2018

To design the practical core-shell electrocatalysts, combination of core and shell materials is important to meet catalytic activity and durability target. In general, Pd is considered as a good core material due to its best activity caused by strain/ligand effect. Preparing Pd nanoparticles can be a starting point in fabricating core-shell type electrocatalysts, much simplified Pd preparing process is suggested by using carbon monoxide (CO) as a reducing agent and/or capping agent. The solvent composition and reaction temperature can control to nanosheet, tetrahedron, and sphere without using additional stabilizer. Among them, Pd nanosheet which has mainly (111) plane showed about 3 times higher electrocatalytic activity for oxygen reduction reaction (ORR) to the spherical Pd nanoparticles. The enhanced ORR activity of Pd nanosheets can be attributed to the exposure of Pd (111) surface and the high electrochemical surface area. Therefore, we demonstrated that the shape of Pd nanomaterials is easily controlled via a facile reduction method using CO, and (111) plane-oriented Pd nanosheets can be a promising ORR catalysts and core material for polymer electrolyte fuel cells (PEFCs).

• Proceedings of the Korean Magnestics Society Conference
• /
• 2007.05a
• /
• pp.283.1-283.1
• /
• 2007

• Proceedings of the PSK Conference
• /
• 2002.10a
• /
• pp.409.1-409.1
• /
• 2002

For the development of a biocompatible nano-scale drug carrier. hydrophilic polysaccharide pullulan was hydrophobized by the conjugation with fatty acid. The synthesized polymers were characterized by the measurements of fourier transform infrared (FT -IR) spectroscopy and 1H -nuclear magnetic resonance (NMR) spectroscopy. In aqueous solution. hydrophobically modified puliulan was self-assembled and structured into the core-shell type nanoparticles. (omitted)

• Bulletin of the Korean Chemical Society
• /
• v.35 no.9
• /
• pp.2813-2817
• /
• 2014

A new magnetic semiconductor material was synthesized to enable separation after a liquid-type photocatalysis process. Core@shell-structured $CuFeS_2@TiO_2$ magnetic nanoparticles were prepared by a combination of solvothermal and wet-impregnation methods for photocatalysis applications. The materials obtained were characterized using X-ray diffraction, transmission electron microscopy, ultraviolet-visible, photoluminescence spectroscopy, Brunauer-Emmett-Teller surface area measurements, and cyclic voltammetry. This study confirmed that the light absorption of $CuFeS_2$ was shifted significantly to the visible wavelength compared to pure $TiO_2$. Moreover, the resulting hydrogen production from the photo-splitting methanol/water solution after 10 hours was more than 4 times on the core@shell structured $CuFeS_2@TiO_2$ nanocatalyst than on either pure $TiO_2$ or $CuFeS_2$.

• Ceramist
• /
• v.22 no.2
• /
• pp.189-197
• /
• 2019

Direct methanol fuel cells (DMFCs) have found a wide variety of commercial applications such as portable computer and mobile phone. In a fuel cell, the catalysts have an important role and durability and efficiency are determined by the ability of the catalyst. The activity of the catalyst is determined by the structure and shape control of the nanoparticles and the dispersion of the nanoparticles and application system. The surface energy of nanoparticles determines the activity by shape control and the nanostructure is determined by the ratio of bi- and tri-metals in the alloy and core-shell. The dispersion of nanoparticles depends on the type of support such as carbon, graphen and metal oxide. In addition, a hybrid system using both optical and electrochemical device has been developed recently.

• Advances in nano research
• /
• v.13 no.5
• /
• pp.427-435
• /
• 2022

Static stability behaviors of annular sandwich plates constructed from two layers of particle-reinforced nanocomposites have been investigated in the present article. The type of nanoscale particles has been considered to be graphene oxide powders (GOPs). The particles are assumed to have uniform and graded dispersions inside the matrix and the material properties have been defined according to Halpin-Tsai micromechanical model. The core layer is assumed to have honeycomb configuration. Annular plate has been formulated according to thin shell assumptions considering geometrical nonlinearities. After solving the governing equations via Galerkin's technique, it is showed that the post-buckling curves of annular sandwich plates rely on the core wall thickness, amount of GOP particles, sector radius, and thickness of layers.

• Journal of Power System Engineering
• /
• v.17 no.1
• /
• pp.104-109
• /
• 2013

Tin and Tinoxide nanoparticles were prepared by arc-discharge nanopowder process. The negative electrode were fabricated using Tin and Tinoxide nanopower. The microstructure and electrochemistry properties were investigated and compared between Tin and Tinoxide. The oxidation film has microstructure of core/shell type and the shell which was attached around Tin nanoparticle consisted of amorphous $SnO_2$. The shape of Tinoxide nanoparticles was formed with irregular shape in comparison with Tin particle. Initial discharge capcity of Tinoxide electrode possesed about 1000mAh/g, which is about 320mAh/g higher than Tin electrode. Irreversible capacity of Tin electrode is much higher than Tinoxide. The cycle performance of Tinoxide electrode was indicated that is batter than Tin. The Tin negative electrode lost most of capacity after 4 cycle but Tinoxide electrode still retained the capacity. The Tinoxide does show some promise as Li-ion battery anode due to their large reversible capacity at low potentials.

• Journal of Powder Materials
• /
• v.17 no.3
• /
• pp.230-234
• /
• 2010

Homogenous silica-coated $CoFe_2O_4$ samples with controlled silica thickness were synthesized by the reverse microemulsion method. First, 7 nm size cobalt ferrite nanoparticles were prepared by thermal decomposition methods. Hydrophobic cobalt ferrites were coated with controlled $SiO_2$ using polyoxyethylene(5)nonylphenylether (Igepal) as a surfactant, $NH_4OH$ and tetraethyl orthosilicate (TEOS). The well controlled thickness of the silica shell was found to depend on the reaction time and the amount of surfactant used during production. Thick shell was prepared by increasing reaction time and small amount of surfactant.