• Bulletin of the Korean Chemical Society
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• 제20권2호
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• pp.147-149
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• 1999

The electronic structures of α- and β-gold selenides are studied. α- and β-AuSe are known as mixed valence compounds having linear (AuSe2, Au+) and square-planar (AuSe4, Au3+) units in their structure simultaneously. Our EHTB calculations, however, show that the oxidation states of Au in α- and β-AuSe are both close to +1. This is because the frontier orbitals are largely made up of Se p-orbitals and Au d-orbitals that lie well below the Fermi level. Our results are consistent with the recent X-ray absorption spectroscopy study on AuSe which show that all Au in the compound exhibit a monovalent state independent of their chemical environments.

• 청정기술
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• 제26권4호
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• pp.251-256
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• 2020

The biocompatibility and plasmonic properties of Au nanoparticles make them useful for photothermal therapy, drug delivery, imaging, and many other fields. This study demonstrated a novel, facile, economic, and green synthetic method to produce gold nanoparticles. Gold nanoparticles (AuNPs) with spherical and triangular shapes were effectively synthesized using only Schisandra chenesis fruit extract as the capping and reducing agent. The shape of the AuNPs could be engineered simply by adjusting the molar concentration of HAuCl4 in the reaction mixture. The as-synthesized AuNPs were characterized using UV-VIS spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), dynamic light scattering (DLS), and energy dispersive X-ray analysis (EDXA). This study revealed that by using the HAuCl4 concentration in the AuNP synthesis, the shape and size of the AuNPs could be controlled by the concentration of HAuCl4 and Schisandra chinensis fruit extract as a surfactant. The as-synthesized AuNPs samples had sufficient colloidal stability without noticeable aggregation and showed the predominant growth of the (111) plane of face-centered cubic gold during the crystal growth. The catalytic efficiency of the AuNPs synthesized using Schisandra chenesis fruit extract was examined by monitoring the catalytic reduction of 4-nitrophenol to 4-aminophenol using Ultraviolet-visible spectroscopy (UV-Vis spectroscopy). The synthesized AuNPs showed good catalytic activity to reduce 4-nitrophenol to 4-aminophenol, revealing their practical usefulness.

• Bulletin of the Korean Chemical Society
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• 제35권3호
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• pp.865-870
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• 2014

Gold nanoparticles (AuNPs) were synthesized by laser (Nd:YAG, ${\lambda}$ = 1064 nm) ablation of a gold target immersed in various aqueous electrolyte solutions (7 mM of LiCl, NaCl, KCl, NaBr, and NaI) as well as in deionized water. The surface plasmon absorption and EDX of AuNPs so produced as well as their TEM images were analyzed to investigate the effects of ambient ions on the growth and aggregation of NPs. The size of AuNPs was reduced by laser ablation in the presence of chloride and bromide ions while it increased drastically when AuNPs were formed in iodide solution. Interestingly, triangular nanoplates were synthesized only in iodide solution. Surface chemistry on AuNPs in various electrolyte solutions was explored to elucidate the role of ions on the size and stability of AuNPs.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.11.2-11.2
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• 2009

Au-Ag 합금 박막에서 화학적으로 덜 안정한 Ag를 선택적으로 에칭하는 dealloying 기법을 통하여 crack-free 나노기공 gold 박막을 Si 기판에 제조하였다. Au-Ag 합금 박막은 두 가지 방법을 이용하였다: 1) thermal 또는 electron beam 증착법을 이용하여 Au 와 Ag 다층 박막을 Si 기판에 증착시킨 후 열처리를 통한 합금 박막제조; 2) co-thermal 증착법을 이용하여 Au-Ag 합금박막을 Si 기판에 직접 증착. Crack-free 나노기공 gold 박막 제조에 적합한 합금조성을 얻기 위하여 증착 속도, 열처리조건, dealloying 조건등을 조절하였다. Perchloric acid, HClO4 전해질을 이용한 전기화학적 dealloying을 통하여 crack-free 나노기공 gold 박막을 제조하였고, 기공크기를 조절할 수 있었다. 이에 더하여, electrophoretic 방법을 이용하여 나노기공 gold와 semiconductive 양자점 (CdTe 또는 CdSe)의 나노복합박막을 형성시킨 후 특성을 분석하였다.

• 치위생과학회지
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• 제9권2호
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• pp.153-160
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• 2009

본 연구는 금속-도재 수복물 제작에 사용되는 Ni-Cr alloy와 Co-Cr alloy, 그리고 티타늄에 gold bonding agent를 도포하여 Au coating 층을 형성하였다. 각 시편의 절단면을 전자현미경으로 Au coating 층과 porcelain bonder, 그리고 불투명 도재간의 결합을 관찰하였고, 각 계면의 상태를 SEM/EDS 방법으로 조사하였다. 실험에서 사용된 재료와 방법의 범위 내에서 다음과 같은 결론을 얻었다. 1. Gold bonding agent를 사용하여 형성한 Au coating 층은 미세다공성을 가진 구조로 판단되었다. 2. Au coating 층과 porcelain bonder 그리고 불투명 도재간의 결합은 잘 일어나 보였다. 3. Au coating 층은 도재 소성과정에서 발생하는 산화층의 확산을 제한하는 것으로 관찰되었다.

• 청정기술
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• 제16권2호
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• pp.117-123
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• 2010

본 연구에서는 Au(I) 이온을 함유한 시안 용액으로부터 다른 형태의 금을 회수하기 위하여 생체흡착 후 탈착하는 방법과 생체흡착 후 회화하는 방법을 제안하였다. 생체흡착제로는 아미노산 발효 공정에서 발생하는 균체 폐기물(Corynebacterium glutamicum)을 사용하였다. 바이오매스의 흡착 특성을 알아 보기 위하여 pH edge 실험을 수행하였으며, 그 결과 흡착성능은 pH 2-3 부근에서 우수한 결과를 보였다. 또한, 등온흡착 실험 결과를 Langmuir 모델에 적용한 결과 Au(I)의 최대 흡착량은 pH 2.5에서 35.15 mg/g이었다. 흡착 속도론 실험을 통해 흡착 평형은 60분 이내의 짧은 시간 내에 이루어지는 것을 확인하였다. Au(I)을 회수하기 위하여 바이오매스에 흡착된 Au(I)을 탈이온수를 이용하여 탈착을 시켰으며, 탈착효율은 91%로 평가되었다. 이 결과는 바이오매스를 이용하여 흡착과 탈착을 통해 1가 금을 효과적으로 회수할 수 있음을 보여준다. 영가 형태로 회수하기 위하여, 금을 흡착하고 있는 생체흡착제를 회화하여 환원된 형태의 금을 성공적으로 회수하였으며, 회분 중 금의 순도는 85% 이상이었다. 따라서 본 연구에서 제시한 생체흡착 후 탈착(1가 형태) 공정과 생체흡착 후 회화(영가 형태) 공정은 회수하고자 하는 금의 산화수에 따라 선택하여 사용될 수 있을 것으로 기대된다.

• 자원환경지질
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• 제29권3호
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• pp.257-267
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• 1996

One hundred of thirty volcanic rocks col1ected from the Jeju island， Jeongog， Guryongpo and other areas were analyzed for major elements and trace elements with Au by inductively coupled argon plasma and graphite furnace atomic absorptiom spectrometry. The Au content is the highest values (0.2~43.4 ppb, average; 10.34 ppb) from the Jeju island volcanic rocks and the lowest (0.5~11.0 ppb, average; 1.23 ppb) from the Guryongpo volcanic area. The content of Au tends to be higher in the Quarternary volcanic rocks than Tertiary or Cretaceous volcanic rocks. The Au content of the calc alkali volcanic rocks tends to increase from mafic to felsic volcanic rocks, but that of the alkalic volcanic rocks tends to increase from felsic to mafic volcanic rocks. The Au content of the volcanic rocks collected from the Jeju island shows the highest values in the feldspar olivine basalts. Elements or oxides which have positive or negative correlations with Au are Ag, Mo, Rb, V, Y, $K_2O$, MgO and $SiO_2$, but other elements analyzed are not shown correlations with Au. It has a tendency to show that samples from the Jeju with 5 ppb gold and more are plotted in the non-Dupal area and those with less than 5 ppb gold in the Dupal area, while those from the Jeongog with 5 ppb gold and more are plotted in the Dupal area and those with less than 5 ppb gold in the non-Dupal area, in the Ba/Nb-La/Nb, Zr/Nb-Ba/Nb diagrams. It shows that samples from the Jeju and Guryongpo with high gold content are plotted in the within-plate, while those with low gold content are plotted in the arc-related area, and those from the Jeongog are scattered in the $TiO_2-Al_2O_3$, $Zr/A1_2O_3-TiO_2/Al_2O_3$ diagrams.

• Journal of the Korean Physical Society
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• 제73권9호
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• pp.1283-1288
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• 2018

In this work, we investigate polarization-dependent excitation of the propagating surface plasmon polariton (SPP) modes in gold nanowires (Au NWs) combined with gold nanoparticles (Au NPs). The light coupling from focused light to SPPs on Au NWs is investigated for different structural combinations of Au NWs with Au NPs, using full-wave finite-element numerical simulations. The results show that the excitation of SPPs changes remarkably on varying the orientation of the NP on NW or the polarization angle of the incident light. Metallic NWs combined with NPs can be applied to the polarization-resolved SPP coupling in various optical and optoelectronic devices including photonic circuits and optical sensors.

• Bulletin of the Korean Chemical Society
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• 제28권3호
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• pp.439-442
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• 2007

A solid state Hg(Au)/HgO reference electrode was prepared utilizing gold amalgam solid particles. Solid fine powder of the gold amalgam was prepared by chemical reduction of Au(III) with NaBH4 followed by reduction of Hg(II) in the presence of gold fine particles. The solid content in the suspension of the gold amalgam particles and fine mercury oxide particles in DMF containing PVC was precipitated by the addition of a large amount of water to give solid Hg(Au)/HgO/PVC mixture. After drying, the mixture was pressure-molded to a physically stable Hg(Au)/HgO composite reference electrode material. The electrochemical characteristics of the electrode as a reference electrode were very similar to an ordinary Hg/HgO reference electrode. The electrode material can be molded and fabricated in any desired shape and size. The surface can be renewed by a simple polishing process whenever contaminated or deactivated. The applicability of the electrode in the electrochemical detection of carbohydrates after anion exchange separation was evaluated.

• Bulletin of the Korean Chemical Society
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• 제32권10호
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• pp.3575-3580
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• 2011

This paper reports a methodology for preparing close-packed two dimensional gold nanoprism films and hexagonal nanoplate films at a hexane/water interface. By controlling the concentration of linker molecules in the hexane layer and the temperature of the colloid solution, highly ordered close-packed nanoplate arrays can be fabricated. These films were investigated to compare their corresponding surface enhanced Raman scattering (SERS) efficiencies. It was demonstrated that the Au nanoprism films resulted in a stronger SERS enhancement than the Au hexagonal nanoplate films. The difference in the SERS enhancement is attributed to the film array difference, demonstrating that Au nanoprism films have a higher line contact density than their Au hexagonal analogues.