• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.156-162
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• 2015

나노입자의 특성과 기능은 bulk 물질과 달리, 나노 입자를 이루는 원소의 종류 뿐만아니라 크기와 모양에도 밀접한 연관이 있다. 이를 계산화학적으로 예측할 수 있다면 나노입자의 합성과 응용에 큰 도움이 될 것이다. 본 연구에서는 일정한 크기의 은 나노입자의 구조를 계산한 뒤, 바깥쪽의 두 원자 층을 무작위로 섞은 뒤 다시 구조최적화 계산을 거쳐 다양한 나노입자들의 구조를 찾았다. 이렇게 구해진 구조들의 에너지를 계산하고 원자를 하나 떼어낼 때의 에너지를 계산하여 응집 에너지를 구해 경향성을 분석해 보았다. 더 나아가, 나노입자를 이루는 각 원자 층의 개수가 하나 더 커질 때 필요한 에너지를 계산하여, 원자 하나당 평균을 내어 분석해보았다. 본 연구에서는 병렬화 된 밀도범함수이론 계산 프로그램을 이용해 100개가 넘는 입자의 계산이 가능하다는 것을 확인했고, 은 나노입자의 크기가 증가함에 따라 원자 하나가 추가되는 경우와, 원자 층 하나가 추가되는 경우의 그래프를 보고 경향성을 분석하였다. 이는 다른 화학적 환경에 있는 은 원자의 에너지를 계산하여 각각의 환경에서의 은 나노 입자의 크기를 예측하는 계산하는 데 초석이 될 것이다.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.7
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• pp.771-776
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• 2005

In recent days, there is much interest in the biocidal activity of silver since silver is known to be safe and effective as disinfectant and biocidal material against coliforms and viruses. In particular, nano silted silver particles which can be used as effective biocidal material received more attention. Accordingly, it is important to investigate antimicrobial activity and mechanism of nano sized silver particles prepared in a cost-effective manner. In this study, nano sized silver particles were prepared via photoreduction of a silver salt ($AgNO_3$) in the bulk phase of $PEO_{20}-PPO_{70}-PEO_{20}$ (Pluronic 123) block copolymer The antimicrobial efficacy of silver nano particles against E. coli was investigated and compared with that of silver ion as the concentration of silver nano particles, pH ($5.6{\sim}8.2$), temperature ($4^{\circ}C{\sim}35^{\circ}C$) varied in aqueous system. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) was used to examine the nature of damaged microorganism with nano sized silver particles and silver ion. This study showed that antimicrobial efficacy of silver nano particles was approximately one twentieth than that of silver ion. It was more biocidal at higher pH in contrast with silver ion. In addition, nano silver particles was demonstrated to disrupt the outer membrane of E. coli, subsequently causing their aggregation. On the other hand, silver ion diffused into the cell damaging the cytoplasmic membrane without disrupting the outer membrane of E. coli.

• Polymer(Korea)
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• v.34 no.4
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• pp.341-345
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• 2010

Effects of modification of silver nanoparticles on the polymerization rate and morphology of poly(methyl methacrylate)(PMMA)/silver microspheres prepared by suspension polymerization of MMA were investigated. The silver nanoparticles and their surface hydrophilicity played an important role in the polymerization rate and the morphology of poly(methyl methacrylate) (PMMA)/silver microspheres. The polymerization rate increased slightly with modified silver nanoparticles. PMMA/silver microspheres with conversion up to 85% were obtained in spite of the low polymerization temperature. Due to the change of hydrophilicity of silver nanoparticles, different appearances of the microspheres having golf ball-like convex surfaces or concave surfaces were observed. As the hydrophilicity of silver was decreased, stable nanocomposites were prepared.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2011.03a
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• pp.55-55
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• 2011

실리카 지지체 위에 은 (silver) 나노 입자를 부착시키는 방법으로는 지지체 표면을 먼저 은입자와 친화성이 큰 amino(-NH2), mercapto(-SH), cyan(-CN) 등의 관능기로 표면처리 하는 방법이 일반적으로 사용된다. 구체적으로 설명하면 첫 단계로 지지체인 실리카입자의 표면을 아민으로 표면 처리 한다. 실리카 입자위에 부착된 아민관능기는 입자 생성의 단계에서 은 (silver) 나노 입자가 붙는 접촉점의 역할과 핵 생성 장소로서의 역할을 하게되고, 아민 관능기의 이런 역할로 실리카 입자 표면에 부착된 핵이 생장하여 입자가 됨으로써 최종적으로 은(silver) 나노 입자가 실리카 지지체위에 부착된 형태의 나노복합체가 형성된다. 분자량이 다른 PVP를 사용하여 제조한, NH2와 SH로 계면처리 된 은-실리카 나노복합체제조를 시도하였다. 사용되는 PVP의 분자량이 증가함에 따라 긴 고분자 사슬에 의하여 생성된 입체장애가 증가하게 되어, 은 핵의 성장에 대한 물리적 장벽이 증가하게 된다. 그러므로 고정화된 은 입자의 크기가 감소하게 된다. 이러한 형상은 NH2기 또는 SH기로 계면 처리된 실리카를 이용하여 제조된 은-실리카 나노복합체 입자들에서 모두 관찰되지만, SH기로 계면처리된 실리카를 사용할 경우 고정화된 은 입자의 수가 더욱 많고, 크기 역시 더욱 균일함을 알 수 있다.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.10
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• pp.936-941
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• 2010

This study was conducted to investigate formaldehyde removals by silver nano-particles attached on the surface of granular activated carbon (Ag-AC) and to compare the results to those obtained with ordinary activated carbon (AC). The BET analysis showed that the overall surface area and the fraction of micropores (less than $20{\AA}$ diameter) of the Ag-AC were significantly decreased because the silver particles blocked the small pores on the surface of the Ag-AC. The formaldehyde removal capacity of the Ag-AC determined using the Freundlich isotherm was higher than that of AC. Despite the decreased BET surface area and micropore volume, the Ag-AC had the increased removal capacity for formaldehyde, presumably due to catalytic oxidation by silver nano-particles. In contrast, the adsorption intensity of the Ag-AC, estimated by 1/n in the Freundlich isotherm equation, was similar to that of the ordinary AC, indicating that the surface modification using silver nano-particles did not affect the adsorption characteristics of AC. In a column experiment, the Ag-AC also showed a longer breakthrough time than that of the AC. Simulation results using the homogeneous surface diffusion model (HSDM) were well fitted to the breakthrough curve of formaldehyde for the ordinary AC, but the predictions showed substantial deviations from the experimental data for the Ag-AC. The discrepancy was due to the catalytic oxidation of silver nano-particles that was not incorporated in the HSDM. Consequently, a new numerical model that takes the catalytic oxidation into accounts needs to be developed to predict the combined oxidation and adsorption process more accurately.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.10-16
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• 2016

This work investigates the size and dispersion characteristics of silver nanoparticles synthesized by a liquid phase reduction method using PAA. The experimental variables were the molecular weight and doses of the PAA, reducing agent, dispersant, and organic solvent (ethanol-acetone). UV-visible spectrophotometer results confirm the formation of the silver particles, and SEM indicates size in the nanometer range. As the ultrasonication time increases, there is a tendency toward smaller agglomerates of nanoparticles. The agglomerates were dispersed into 1-5 agglomerates of particles by ultrasonication for 3 hours or more. Relatively spherical nanoparticles were produced with a completely homogeneous dispersion and size of 49.56-85.75 nm by ultrasonication using BYK-192, a dispersant containing copolymer with a pigment affinic group. The average size of the silver nanoparticles was increased to 36.82, 50.66, and 56.06 nm with increasing molecular weight of PAA. Also, the size of the nanoparticles increased with the capping of PAA on the surfaces of the nanoparticles when increasing the amount of PAA. The addition of hydrazine as a reducing agent produced relatively small particles because many nuclei were created by the reduction reaction. The ethanol-acetone solvent helped with the regular arrangement of the silver nanoparticles.

• Particle and aerosol research
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• v.12 no.3
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• pp.95-102
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• 2016

Controlling exposures to occupational hazards is important for protecting workers. Certified facepiece respirators are recommended when engineering controls do not adequately prevent exposures to airborne nanomaterials. The objective of this study is to carry out the experimental performance test to investigate the fractional efficiencies of the filter media for two grades of facepiece respirators. Experimental performance evaluations were carried out for the test NaCl particles and silver nanoparticles. For media of respirator filter, the penetration of NaCl particles was less than 5% and the most penetrating particle size occurred at about 40 nm. For silver nanoparticles, the most penetrating particle size was about 20nm with higher efficiency than those of NaCl particles. Charge characteristics of airborne nanoparticles is important because the media of respirator filter is made by the electret filter media.

• Journal of the Korean Chemical Society
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• v.57 no.5
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• pp.618-624
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• 2013

We demonstrated unique inter- and intra-plasmonic coupling effects in bimetallic Au@Ag core-shell NP arrays which are regularly or randomly arranged on self-assembled block copolymer (BCP) inverse micelle monolayers. Polyvinylpyrrolidone (PVP)-stabilized Au@Ag core-shell NP arrays in regular or disordered configuration were incorporated and assembled on reconstructed PS-b-P4VP inverse micelle templates through two types of processes. The intensively enhanced LSPR coupling properties of individual and assembled Au@Ag NPs were evaluated by UV-visible spectroscopy in terms of the type of ligand stabilizer, coupling between Au and Ag, thickness of Ag shell, and type of array configuration. Finally, Au@Ag core-shell NP arrays were employed as active substrates for surface enhanced Raman spectroscopy (SERS) and a significantly enhanced signal enhancement was observed in accordance with the coupling intensity of Au@Ag NPs patterns.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.772-779
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• 2016

Silver nanoparticles were prepared by reacting silver nitrate and trisodium citrate in an aqueous solution. Their size and shape were investigated by scanning electron microscopy (SEM). The synthesis was carried with different silver nitrate concentration, addition of TSC, solvent, surfactant, ultrasonication, and dispersing agent. With higher concentration of silver nitrate or TSC, the particles became large or agglomerated. The SEM results showed that the nanoparticles have spherical and pseudospherical shape with a narrow size distribution. The hydrophobic solvent did not affect the dispersibility, but the hydrophilic solvent enhanced it. The addition of HPMC surfactant caused the size to increase (50-100 nm) with non-uniform shapes and partial agglomeration. The dispersibility was significantly improved by ultrasonication for over 3 hours after the addition of a dispersing agent. Complete dispersion was achieved by adding the dispersant, and the nanoparticle sizes were as follows: 30-40 nm (BYK-182) < 42-78 nm (BYK-192) < 51-113 nm (BYK-142). The nanoparticles were 38.45-46.28 nm after the addition of 2-4 wt% TSC in 0.002 M silver nitrate solution.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.276.1-276.1
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• 2016

본 연구에서는 차세대 유연 투명 히터 (Flexible and transparent heater) 제작을 위한 ATO 나노입자-은 네트워크 하이브리드 투명 전극의 특성을 연구하였다. 최적화된 은 네트워크 (Self-assembled Ag network) 투명 전극 상에 20-30 nm의 직경을 가지는 ATO (Sb-doped $SnO_2$) 나노입자를 스프레이 방식으로 상압, 상온에서 코팅하여 인쇄형 ATO-은 네트워크 하이브리드 투명 전극을 구현하였다. 스프레이로 코팅된 투명 ATO 나노 입자는 은 네트워크 전극의 빈 공간을 매워 줌으로써 은 네트워크 간의 연결성 및 표면 조도를 낮춰주어 유연 투명 히터 작동 시 전류의 집중 현상을 막아줄 수 있다. ATO-은 네트워크 하이브리드 투명 전극의 최적화를 위해 스프레이 횟수에 따른 하이브리드 투명 전극의 전기적, 광학적, 표면 특성을 분석하였으며, 최적의 조건에서 14 Ohm/square의 면저항과 66%의 투과도를 가지는 하이브리드 투명 전극을 구현하였다. 또한 FESEM 분석을 통해 ATO-은 네트워크 하이브리드 전극의 표면 및 계면 구조를 연구하고 ATO 코팅이 은 네트워크 전극의 특성에 미치는 영향을 규명하였다. 최적화된 ATO-은 네트워크 하이브리드 투명 전극을 이용하여 유연 투명 히터를 제작하고 전압에 따른 히터의 온도의 변화를 측정하여 차세대 유연 투명 히터용 투명 전극으로 인쇄기반 ATO-은 네트워크 하이브리드 투명 전극의 가능성을 확인하였다.