• Economic and Environmental Geology
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• v.52 no.6
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• pp.595-604
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• 2019

The purpose of this study was simply to obtain gold through a microwave-nitric acid experiment of invisible gold concentrate with the use of filter paper. For the purpose, this study conducted a microwave-nitric acid leaching experiment and examined nitric acid concentration. As a result of the experiment, this study discovered that Fe, Te and Ag were completely leached in the leaching solution whereas Au was not determined in all of the nitric acid conditions. The leaching solution was filtered with three filter papers and then these filter papers were analyzed with SEM/EDS. As a result of the EDS analysis, Au was detected in all of the surface and cross-section of the 1st, 2nd and 3rd filter papers. As the three filter papers containing solid-residue were analysed in the lead-fire assay, gold particles were found in all of the nitric acid conditions. In the lead-fire assay, maximum gold(452.50g/t) was recovered when nitric acid concentration was 6M and microwave leaching time was 12mins.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.6
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• pp.379-382
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• 2019

Synthesis of gold nanoparticles (NPs) made an aqueous environment via the reduction of HAuCl₄ by ascorbic acid (AC) with the surfactant of polyvinylpyrrolidone (PVP). Highly monodisperse gold particles with size ranges from 4 to 20 nm were prepared in high-yield by pH control. The synthesized gold nanoparticles were analyzed for structural and optical properties using transmission electron microscopy (TEM) and UV-vis spectroscopy. In this study, we could reveal that the prepared nanoparticles exhibited efficient surface-enhanced Raman scattering (SERS) properties, and their SERS activities depends on size.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.515-519
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• 2015

Complexes composed of hydrogen tetrachloroaurate (III) trihydrate ($HAuCl_4{\cdot}3H_2O$) and DNA were first formed for the synthesis of gold nanoparticle using a DNA template, which were validated using UV-Vis spectroscopy. The morphology of complexes were also characterized by scanning electron microscopy (SEM). DNA-mediated gold nanoparticles were synthesized by the chemical reduction of DNA-Au(III) complexes using hydrazine ($N_2H_4$) and sodium borohydride ($NaBH_4$) as reducing agents. The effects of reducing agent types and their concentration on the formation of gold nanoparticles were investigated. The results showed that hydarazine was the most effective for the reduction of DNA-Au(III) complex. The DNA-mediated gold nanoparticles were characterized SEM, particle size analyzer (PSA), and transmission electron microscopy (TEM). Gold nanoparticles with 55~80 nm in diameter were formed by the aggregation of smaller gold nanoparticles (~nm), which was confirmed in the DNA matrix.

• Elastomers and Composites
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• v.43 no.4
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• pp.264-270
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• 2008

$\alpha$-D-mannosyl fullerene[$C_{60}$]-functionalized gold nanoparticle films were selfassembled using the layer-by-layer method on the reactive of glass slides functionlized with 3-aminopropyltrimethoxysilane. The functionalized glass slides were alternately soaked in the solutions containing $\alpha$-D-mannosyl fullerene[$C_{60}$] and 4-aminothiophenoxide/hexanethiolate-protected gold nanoparticles. $\alpha$-D-mannosyl fullerene[$C_{60}$]-functionalized gold nanoparticle films have grown up to 5 layers depending on the immersion time. The self-assembled nanoparticle films were characterized using UV-vis spectroscopy showed that the surface plasmon band of gold at 530 nm gradually became more evident as successive layers were added to the films.

• Journal of the Mineralogical Society of Korea
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• v.32 no.2
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• pp.113-126
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• 2019

This study aimed to effectively dissolve sulfide minerals through microwave-nitric acid leaching of invisible gold concentrate and then recover gold from the solid-residue with fire assay. For the purposes, this study conducted microwave-nitric acid leaching experiments to examine nitric acid concentration, time of microwave leaching, and sample addition effect. As results of the experiments, this study discovered that the weight loss rate of solid-residue increased as nitric acid concentration and microwave leaching time increased while weight loss rate decreased as sample addition increased. In an XRD analysis with solid-residue, it was discovered that pyrite completely disappeared when the nitric acid concentrate was 6 M and the microwave leaching time was 18 minutes. When a fire assay was carried out with solid-residue, gold particles with more content were recovered as nitric acid concentration and microwave leaching time increased whereas gold particles with more gold content were recovered as the sample addition decreased.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.32-36
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• 2016

단일금속 나노입자에 비해 나노합금입자는 발광이나 촉매력과 같은 여러 특징들이 더 뛰어나게 나타난다고 잘 알려져 있다. 이에 따라 실험적인 연구뿐 아니라 이론적으로도 나노합금입자의 특성과 구조를 밝히려는 노력이 이루어지고 있다. 그러나 대부분의 연구는 자유공간을 상정하여 진행되고 있어, 갇힌 공간 속의 입자에 대한 연구는 부족한 실정이다. 이러한 배경으로 본 연구에서는 Sutton-Chen (SC) 포텐셜을 주요 이론으로 하여, 복제교환분자동력학(replica exchange molecular dynamics, REMD) 모의실험을 통해 가두는 공간의 크기에 따라 금-팔라듐 나노합금입자(Au17Pd17)의 구조와 특성이 어떻게 달라지는지 EDISON에 등록된 metal_alloy 프로그램(molecular dynamics simulation of metal alloy nano-cluster)을 사용해 살펴보았다. 결과적으로 입자가 상전이 이전의 낮은 온도에서 존재하면, 둘러싼 공간의 크기와 무관하게 안정한 구조의 중심에 항상 팔라듐 원자가 위치한다는 것이 확인되었다. 또, 가두는 공간의 크기마다 상전이가 일어나는 온도 구간의 차이가 나타났으며, 작은 공간에 갇힌 입자일수록 입자의 최대 직경이 작아지면서 상대적으로 높은 에너지를 가지는 구조를 형성하였다. 이는 입자가 존재하는 공간이 좁을수록 에너지의 증가를 통하면서 최대한 공간을 활용할 수 있는 구조를 선택하는 것으로 보인다.

• Elastomers and Composites
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• v.34 no.1
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• pp.45-52
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• 1999

This paper describes how the gold particles self assemble on the specific phase on the microphase separated block copolymer thin film and form a well ordered patterns. For this study, polystyrene-polybutadiene-polystyrene (PS-PB-PS) triblock copolymer (30wt % PS) thin films (${\sim}100nm$) having a cylindrical morphology were cast from 0.1wt% toluene solution to be used as polymer thin film templates. The films having either vertical PS cylinders or in-plane PS cylinders in PB matrix from each different solvent evaporation condition were obtained. Cross-sectional transmission electron microscopy(TEM) was used to study the surface and bulk morphologies of block copolymer thin films. Small amount of gold particles was evaporated on a block copolymer thin film template to obtain a nano-scale pattern. When an as-cast thin film template was used, gold particles preferentially self assemble on the low surface tension PB phase and a relatively well ordered pattern in nano-scale was produced. However, after the formation of a low surface energy PB rich layer upon annealing, a gold self-assembled pattern was not observed.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.2
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• pp.39-46
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• 2013

In this paper, organic solar cells(OSCs) based on bulk-heterojunction structures were fabricated by spin coating method using polymer P3HT and fullerene PCBM as a photoactive layer. The fabricated OSCs had a simple glass/ITO/PEDOT:PSS/P3HT:PCBM/Al structures. The photoactive layer of mixed P3HT:PCBM was formed with 1:1 weight ratio. The hole transport layer(HTL) was used conducting polymer PEDOT:PSS concentration with gold nanoparticles. The annealing temperature and concentration of nanoparticles in HTL were verified to improve the OSC characterization. The percentage of gold nanoparticles in HTL were 0.5 wt% and 1.0 wt%, and the surface morphology, electrical properties and absorption intensities were investigated. The devices were 0.5 wt%, and the highest 3.1% of the powder conversion efficiency(PCE), 10.2 $mA/cm^2$ of the maximum short circuit current density($J_{SC}$), 0.535V of the open circuit voltage($V_{OC}$) and 55.8% of the fill factor(F.F) could be obtained when the nanoparticle concertration was 0.5 wt%. The annealing temperature of HTL was $110^{\circ}C$, $130^{\circ}C$, $150^{\circ}C$ in vacuum oven and measured the absorption intensities, surface morphology, crystallinity and electrical properties were investigated. The best property was obtained in HTL annealed at $130^{\circ}C$ for gold nanoparticles of 0.5 wt%, showing that $J_{SC}$, $V_{OC}$, F.F and PCE were about 12.0 $mA/cm^2$, 0.525V, 64.2% and 4.0%, respectively.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.89.2-89.2
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• 2012

$150^{\circ}$ 이상의 접촉각을 가지는 초소수성 표면은 self-cleaning, anti-fingerprint, anti-contamination 등의 특성을 가지므로 전자, 도료, 자동차 등 다양한 산업에서 활용될 수 있다. 재료 표면의 친/소수성은 물리적 요인과 화학적 요인 두 가지 요인을 조절함으로써 제어할 수 있다. 즉, 표면의 거칠기를 크게 하거나 표면에너지를 낮춰줌으로써 초소수성 표면을 구현할 수 있다. 실리카는 자연계에 매우 풍부하게 존재하고 있으며, 생체무해하며 내구성과 내마모성, 화학적 안정성, 고온 안정성 등을 지니고 있어 박막소재로 이용하기에 우수한 특징을 지니고 있다. 이러한 실리카 초소수성 코팅층을 형성하는 방법으로 본 연구에서는 전기분무법으로 마이크로 크기의 실리카 입자로 형성된 코팅층을 형성하였다. 이러한 마이크로 구조의 표면거칠기를 더욱 높이기 위하여 금 나노입자를 부가적으로 형성시켜 마이크로-나노구조 혼성의 계층구조를 만들고자 하였다. 금 나노입자는 자외선 조사 광환원법을 사용하였고, 이러한 계층구조에 플루오린 처리를 하여 계층구조 초소수성 코팅층을 형성하였다. 계층구조를 가지는 실리카 코팅층은 물 이외에 표면장력이 낮은 용액에서도 높은 접촉각을 보였고, 이러한 코팅층의 고온 안정성과 내구성, UV 저항성 등을 조사하여 실제 응용 가능성을 검토하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.191-191
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• 2012

유체 플라즈마 공정(SPP)은 고에너지를 가지는 플라즈마를 유체 내에 발생시키는 공정으로서 나노유체 및 촉매 물질 제조 등 여러 가지 응용분야에 적용할 수 있다. 본 연구에서는 SPP 공정을 이용하여 금 나노입자를 합성하였고 전압과 방전시간의 변화에 따른 금나노 입자의 환원속도를 분석하였다.