• 자원환경지질
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• 제21권3호
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• pp.223-234
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• 1988

A large number of gold and/or silver-bearing quartz veins occur in or near Mesozoic granite batholith elongated in a NE-SW direction within the Chungcheong Province. Precambrian schists and gneisses, and Jurassic and Cretaceous granitic rocks serve as hosts for gold and/or silver deposits. On the basis of Ag/Au total production and ore grade ratio, 15 mines may be divided into three major groups: gold-dominant deposits, gold-silver deposits, and silver-dominant deposits. The chemical composition of electrum from skarn deposit (Geodo mine), alaskite-type deposit (Geumjeong mine) and 15 vein deposits was summarized. It was found that the Au content of electrum for vein deposits ranging from 5.2 to 86.5 is lower than that for skarn and alaskite deposits. Among 15 vein deposits, the composition of electrum associated with pyrrhotite is relatively high and has a narrow range of 40.8 to 86.5 atomic % Au, but the Au content of electrum with pyrite is in range of 5.2 to 82.8 atomic %, and is clearly lower than that with pyrrhotite. The grouping of ages for these mines indicates that gold and/or silver mineralizations occurred during two periods in the Mesozoic. Daebo igneous activities are restricted to gold mineralization in the range of 158 to 133 Ma, whereas Bulgugsa igneous activities are related to gold and/or silver mineralization ranging from 108 to 71 Ma. Generally speaking, Jurassic gold-dominant veins have many common characteristics; notably prominent association with pegmatites, simply massive vein morphology, high fineness in the ore concentrates, rarity of silver minerals, and a distinctively simple mineralogy, including sphalerite, galena, chalcopyrite, pyrrhotite and/or pyrite. Although individual deposits exhibit widely differing diversity, Cretaceous gold-silver and silver-dominant veins are characterized by features such as complex vein, low to medium fineness in the ore concentrates and abundance of silver minerals including Ag sulfosalts, Ag sulfides, Ag tellurides and native silver.

• 접착 및 계면
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• 제24권2호
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• pp.54-59
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• 2023

은 나노와이어 기반 투명전극은 우수한 전도도와 투과도, 유연성을 가지고 있어 ITO 기반의 유연전극을 대체할 수 있는 차세대 유연투명전극으로 각광받고 있다. 그러나 은 나노와이어 기반 투명전극 제작에 사용되는 은 나노와이어 용액에 대한 이해가 부족하여 전자소자 응용 시 소자의 비정상적인 작동이나 전극 필름의 박리 문제가 종종 발생하곤 한다. 본 연구에서는 은 나노와이어 용액에 대한 이해를 높이고자 은 나노와이어 용액에 사용되는 첨가제 중 하나인 hydroxypropyl methylcellulose 접착력 증진제에 대한 연구를 진행하였으며, 접착력 증진제를 첨가함에 따라 은 나노와이어 용액의 특성이 어떻게 변화되고 이러한 용액을 사용하여 제작된 은 나노와이어 필름의 특성이 어떻게 변화되는지 연구하였다. 용액의 특성으로는 극성성분의 표면장력과 분산 성분의 표면장력이 측정되었으며, 필름 특성으로는 표면 에너지와 표면 형상, 은 나노와이어 밀도, 면저항 등이 분석되었다.

• 대한소아치과학회지
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• 제51권1호
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• pp.80-87
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• 2024

Silver diamine fluoride, which can arrest dental caries, is alkaline and may cause mild soft tissue irritation. Water-based silver fluoride has a neutral pH, which is closer to the physiological range, and is biocompatible for use in the oral environment. This study aimed to evaluate the effect of water-based silver fluoride on remineralizing early enamel lesions by comparing it with other fluoride agents through microhardness and quantitative light-induced fluorescence measurements. An in vitro study with intact bovine incisors was performed. Artificial enamel lesions were induced and subjected to microhardness and quantitative light-induced fluorescence testing. Specimens were randomly divided into 4 groups for treatment. The specimens in group I were treated with water-based silver fluoride and potassium iodide, group II with silver diamine fluoride and potassium iodide, group III with sodium fluoride varnish, and group IV with distilled water. After 8 days of pH cycling, the specimens were subjected to microhardness and quantitative light-induced fluorescence testing. Water-based silver fluoride and silver diamine fluoride showed the greatest increases in microhardness and quantitative light-induced fluorescence, with no significant differences between the two. Sodium fluoride varnish also exhibited a significant increase in microhardness and quantitative light-induced fluorescence, but the differences were smaller than those for water-based silver fluoride and silver diamine fluoride. Water-based silver fluoride is considered useful in a clinical setting for remineralizing enamel lesions, with the advantages of no risk of tissue burn and improved taste and smell.

• 생명과학회지
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• 제18권9호
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• pp.1186-1193
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• 2008

방글라데시 미멘싱에 소재하는 양식어장에서 pangasiid catfish (Pangasius hypophthalmus), silver carp (Hypophthalmichthys molitrix)와 catla (Catla catla)의 조합과 혼합비를 달리하여 16주간 복합양식하였을 때, 이들 어종의 성장률을 조사하였다. 헥타르당 30,000개체의 밀도로 복합양식하여 성장률을 측정하였으며, 혼합조성비는 다음과 같다: 실험구(treatment) 1은 pangasiid catfish와 silver carp을 1:1비율로, 실험구 2는 pangasiid catfish와 cata를 1:1비율로, 실험구 3과 4는 pangasiid catfish, silver carp과 catla를 각각 2:1:1과 3:2:1비율로 복합양식하였다. 양식환경에 영향을 주는 수온, 투명도, 용존산소량, pH, $NO_{3}-N$, $PO_{4}-P$, 엽록소 a와 같은 몇몇 물리화학적, 생물학적 요인과 플랑크톤의 군집을 정기적으로 조사하였다. 어류의 성장속도는 비 성장율(specific growth rate), 일간 체중 증가(daily weight gain)와 체중증가 비율(percent weight gain)을 측정하였다. Pangasiid catfish의 성장률과 사료이용률은 모든 실험구에서 유사하게 나타났다. Silver carp의 성장률은 모든 실험구에서 유의한 차이를 나타내었는데(p<0.05), 양식밀도가 증가할수록 성장률이 현저하게 감소하였으며, Silver carp의 밀도가 가장 낮은 복합양식 조성인 pangasiid catfish, silver carp과 catla의 비율이 각각 2:1:1일 때, silver carp의 성장률이 가장 높게 나타났다. Silver carp의 밀도가 증가할수록 catla의 성장률이 현저하게 감소하는 것으로 나타나, catla의 성장률은 silver carp의 유무에 영향을 받는 것으로 판단되었다. Catla의 성장률은 pangasiid catfish와 calta의 비율이 1:1일 때, 가장 높은 것으로 나타났다. 양식수율과 경제적 이익은 실험구에 따라 현저하게 다른 양상을 보였다(p<0.05). 가장 높은 양식수율과 경제적 이익은 pangasiid catfish, silver carp과 catla를 각각 2:1:1 비율로 양식한 결과에서 얻어졌는데, 이는 silver carp의 높은 성장률과 catla의 시장 단가가 높은 것에 기인하는 것으로 나타났다. 모든 실험구의 수질 상태는 양식기간 동안 적절한 수준을 유지하였으며, 각각의 값은 모든 실험구에서 뚜렷한 차이를 보이지 않았다(p<0.05).

• 생체재료학회지
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• 제22권4호
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• pp.328-336
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• 2018

Background: Biogenic fabrication of silver nanoparticles from naturally occurring biomaterials provides an alternative, eco-friendly and cost-effective means of obtaining nanoparticles. It is a favourite pursuit of all scientists and has gained popularity because it prevents the environment from pollution. Our main objective to take up this project is to fabricate silver nanoparticles from lichen, Usnea longissima and explore their properties. In the present study, we report a benign method of biosynthesis of silver nanoparticles from aqueous-ethanolic extract of Usnea longissima and their characterization by ultraviolet-visible (UV-vis), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analyses. Silver nanoparticles thus obtained were tested for antimicrobial activity against gram positive bacteria and gram negative bacteria. Results: Formation of silver nanoparticles was confirmed by the appearance of an absorption band at 400 nm in the UV-vis spectrum of the colloidal solution containing both the nanoparticles and U. longissima extract. Poly(ethylene glycol) coated silver nanoparticles showed additional absorption peaks at 424 and 450 nm. FTIR spectrum showed the involvement of amines, usnic acids, phenols, aldehydes and ketones in the reduction of silver ions to silver nanoparticles. Morphological studies showed three types of nanoparticles with an abundance of spherical shaped silver nanoparticles of 9.40-11.23 nm. Their average hydrodynamic diameter is 437.1 nm. Results of in vitro antibacterial activity of silver nanoparticles against Staphylococcus aureus, Streptococcus mutans, Streptococcus pyrogenes, Streptococcus viridans, Corynebacterium xerosis, Corynebacterium diphtheriae (gram positive bacteria) and Escherichia coli, Klebsiella pneuomoniae and Pseudomonas aeruginosa (gram negative bacteria) showed that it was effective against tested bacterial strains. However, S. mutans, C. diphtheriae and P. aeruginosa were resistant to silver nanoparticles. Conclusion: Lichens are rarely exploited for the fabrication of silver nanoparticles. In the present work the lichen acts as reducing as well as capping agent. They can therefore, be used to synthesize metal nanoparticles and their size may be controlled by monitoring the concentration of extract and metal ions. Since they are antibacterial they may be used for the treatment of bacterial infections in man and animal. They can also be used in purification of water, in soaps and medicine. Their sustained release may be achieved by coating them with a suitable polymer. Silver nanoparticles fabricated from edible U. longissima are free from toxic chemicals and therefore they can be safely used in medicine and medical devices. These silver nanoparticles were stable for weeks therefore they can be stored for longer duration of time without decomposition.

• Korean Membrane Journal
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• 제8권1호
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• pp.43-49
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• 2006

Complex membranes consisting of silver salt ($AgBF_4,\;AgCF_3SO_3,\;AgSbF_6,\;AgNO_3$) and poly(vinyl alcohol) (PVA) or crosslinked PVA (CPVA) were prepared and tested for the separation of propylene/propane mixtures. For the tested membranes, the complex membranes containing $AgBF_4$ exhibited the highest separation properties, i.e., approximately 20 GPU ($1 GPU=10^{-6}cm^3 (STP)/(cm^2 sec cmHg)$) and 100 of selectivity at 0.2 of silver mole fraction. The CPVA membranes containing silver salt always showed higher selectivity than PVA membranes, presenting silver ions coordinated to -CHO are more effective than those to -OH groups. The threshold silver concentration of CPVA membranes was lower than that of PVA membranes, which might be due to stronger interaction of silver ions with -CHO than that with -OH. The composition at which the selectivity is the highest did not significantly depend on the crosslinking, but did on the kind of silver salt.

• 한국의류학회지
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• 제29권6호
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• pp.805-813
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• 2005

In recent years, greatly increased incidences of diseases made people more concerned about their hygienic environment. Since clothes are the closest environment to man, many methods have beef proposed to impart antimicrobial properties to the textiles. Benefits associated with incorporating antimicrobial properties in textiles include protection to the wearer from microbiological attack, and prevention of odor from perspiration. Silver has been known to kill 650 different disease organisms, however, nano-sized silver particles are known as skin friendly and does not cause skin irritation. In this study, we have examined the antimicrobial effects of cotton or polyester fabric, on which nano-sized silver particles were treated. Colloidal silver solution made by electrolysis of $99.9\%$ silver stick was more effective than that by reduction of $AgNO_3.\;0.7\%$ concentration of colloidal silver solution by electrolysis is helpful to give reduction of $99.9\%$ S. aureus and K. pneumoniae on a cotton fabric without the decrease of whiteness. Since the structures of fiber and fabric effect on their antimicrobial property, PET filament fabric didn't have sufficient antimicrobial properly. The fabrics treated with up to $5\%$ colloidal silver solution didn't have the properly of antistatic and electromagnetic shield.

• 폴리머
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• 제35권5호
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• pp.390-394
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• 2011

현탁중합에 의한 폴리(비닐 아세테이트)((poly(vinyl acetate)(PVAc))/은 미세입자 제조시 사용된 은 나노입자가 중합속도 및 PVAc 미세입자의 형태에 미치는 영향을 고찰하였다. 주사전자현미경, 투과전자현미경, X선 회절, 원자흡수분광분석법을 이용하여 제조된 미세입자의 형태와 특성을 분석한 결과, 사용된 은 나노입자 표면의 친수성 정도와 계면활성제의 농도에 따라 미세입자의 표면이 골프공 표면처럼 오목해지거나 다양한 형태의 중공 구조를 가지는 PVAc/은 미세입자가 제조됨이 관찰되었다. 계면활성제로 개질된 은 나노입자를 이용하여 중합한 경우에 중합속도가 약간 증가하였으며, 80% 이상의 전환율을 가지는 PVAc/은 미세입자를 제조할 수 있었다.

• 한국표면공학회지
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• 제32권3호
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• pp.447-451
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• 1999

Silver has the highest electrical conductivity of all metals and consequently this property is an attractive feature which makes it a leading candidate for use in electronic devices. The research conducted was focused primarily on the development of a process for obtaining a deposited silver-coating onto alumina, for applications related to electrical-conducting devices and, ancillarily, catalysts. Alumina balls and plane substrates were utilized for the investigation. The coating process employed an aqueous ammoniacal silver-nitrate electrolytes with a formaldehyde solution as the reductant. Modifying additives-an activator which would be expected to promote good deposition-characteristics onto the (dielectric) substrate and an inhibitor which would obviate homogeneous reduction (precipitation) of silver was observed when the activator-containing silver-electrolyte reductant constituents were combined. However, the silver-electrolyte/reductant system with inhibitor could be employed (at 8$0^{\circ}C$) to achieve a viable (subject to future research optimization) coating on alumina. The influence of the processing temperature on the deposition process was delineated during the course of the research. The morphology of the deposited-silver on the alumina balls was assessed by SEM imaging. A tape-peel test was employed, with the plane substrates, to semi-quantitatively characterize the adhesion to the alumina.

• 방사선산업학회지
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• 제6권3호
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• pp.273-279
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• 2012

Silica hybrid silver nanoparticles showing the strong antimicrobial activity, in which nano-silver is bound to silica molecules, has been synthesized using ${\gamma}-irradiation$ at room temperature. The present study relates to an antimicrobial composition for coating fiber products comprising silica hybrid silver nanoparticles. In this study, we describe antimicrobial fiber products coated with the silica hybrid silver nanoparticles and a method of antimicrobially treating fiber products by coating the fiber products with the silica hybrid silver nanoparticles. The antimicrobial fiber products exhibited excellent antimicrobial effects. In detailed practice, when the present composition comprising nanosized silica-silver was applied to a cloth (fabric) in a concentration of $6.4mg\;yard^{-1}$, the viable cell number decreased to less than 10 cells before and after laundering, resulting in a reduction of 99.9% or greater in the viable cell number. The present composition displays long-lasting potent disinfecting effects on bacteria. Also, we investigated the toxicity of silica hybrid silver nanoparticles in rats. The skin of rats was treated with a 30 ppm nanoparticles solution ($2ml\;Kg^{-1}$) for 8 days. No toxicity was detected in the treatment. These results suggest that the fiber products coated with the silica hybrid silver nanoparticles can be used to inhibit the growth of various microorganisms.