• Mycobiology
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• 제39권3호
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• pp.194-199
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• 2011

Pepper anthracnose caused by Colletotrichum species is one of the most important limiting factors for pepper production in Korea, its management being strongly dependent on chemicals. The aim of this work was to evaluate the possibilities of using silver nanoparticles instead of commercial fungicides. In this study, we evaluated the effect of silver nanoparticles against pepper anthracnose under different culture conditions. Silver nanoparticles (WA-PR-WB13R) were applied at various concentrations to determine antifungal activities in vitro and in the field. The application of 100 ppm concentration of silver nanoparticles produced maximum inhibition of the growth of fungal hyphae as well as conidial germination in comparison to the control in vitro. In field trials, the inhibition of fungi was significantly high when silver nanoparticles were applied before disease outbreak on the plants. Scanning electron microscopy results indicated that the silver nanoparticles caused a detrimental effect on mycelial growth of Colletotrichum species.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.166.1-166.1
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• 2014

We have controlled the graphene surface in two ways to improve the device performance of optoelectronics based on graphene transparent conductive films. We controlled multilayer graphene (MLG) work function and localized surface plasmon resonance wavelength using a silver nanoparticles formed on graphene surface. Graphene substrates were prepared using a chemical vapor deposition and transfer process. Various size of silver nanoparticles were prepared using a thermal evaporator and post annealing process on graphene surface. Silver nanoparticles were confirmed by using scanning electron microscopy (SEM). Work functions of graphene surface with various sizes of Ag nanoparticles were measured using ultraviolet photoelectron spectroscopy (UPS). The result shows that the work functions of MLG could be controlled from 4.39 eV to 4.55 eV by coating different amounts of silver nanoparticles while minimal changes in the sheet resistance and transmittance. Also the Localized surface plasmon resonance (LSPR) wavelength was investigated according to various sizes of silver nanoparticles. LSPR wavelength was measured using the absorbance spectrum, and we confirmed that the resonance wavelength could be controlled from 396nm to 425nm according to the size of silver nanoparticles on graphene surface. To confirm improvement of the device performance, we fabricated the organic solar cell based on MLG electrode. The results show that the work function and plasmon resonance wavelength could be controlled to improve the performance of optoelectronics device.

• 상하수도학회지
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• 제29권1호
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• pp.77-88
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• 2015

Soil column experiments were evaluated effects of silver nanoparticles (i.e., 0, 2.5, 5, and 10 mg/L) on the microbial viability which is strongly associated with the degradation of organic matter, pharmaceutically active compounds(PhACs) and biological oxidation of nitrogenous compounds during river bank filtration. The addition of silver nanoparticles resulted in almost no change in the aqueous matrix. However, the intact cell concentration decreased with addition of silver nanoparticles from 2.5 to 10 mg/L, which accounted for 76% to 82% reduction compared to that of control (silver nanoparticles free surface water). The decrease in adenosine triphosphate was more pronounced; thus, the number and active cells in aqueous phase were concurrently decreased with added silver nanoparticles. Based on the florescence excitation-emission matrix and liquid chromatograph - organic carbon detection analyses, it shows that the removal of protein-like substances was relatively higher than that of humic-like substances, and polysaccharide was substantially reduced. But the extent of those substances removed during soil passage was decreased with the increasing concentration of silver nanoparticles. The attenuation of ionic PhACs ranged from 55% to 80%, depending on the concentration of silver nanoparticles. The attenuation of neutral PhACs ranged between 72% and 77%, which was relatively lower than that observed for the ionic PhACs. The microbial viability was affected by silver nanoparticles, which also resulted in inhibition of nitrifiers.

• Bulletin of the Korean Chemical Society
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• 제32권2호
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• pp.553-558
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• 2011

Copolymeric silver nanocomposite hydrogels were synthesized by using acryloyl phenylalanine (APA), N'-isopropylacrylamide (NIPAM) and crosslinked by N,N-methylene bisacrylamide (MBA) via radical redox polymerization. Present study allows entrapping silver nanoparticles into hydrogel networks. UV-visible spectroscopy and X-ray diffraction (XRD) studies confirmed the formation of silver nanoparticles in hydrogel matrix. 11% of weight loss difference between hydrogel and silver nanocomposite hydrogel is clearly indicates the formation and silver nanoparticles by thermo-gravimetrical analysis. The order of swelling capacity values of hydrogels and silver nanocmposite hydrogels were found to be in the order of placebo copolymeric hydrogel >Ag-copolymeric silver nanocomposite hydrogels. The particle size of silver nanoparticles was analysed and are in the range of 5 - 10 nm which has been confirmed by transmission electron microscopy (TEM) as well as particle size analysis. The silver nanocomposite hydrogel has shown very good antibacterial activity on gram-positive and gram-negative bacteriocides.

• Journal of Microbiology and Biotechnology
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• 제20권7호
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• pp.1061-1068
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• 2010

The biological synthesis of nanoparticles has gained considerable attention in view of their excellent biocompatibility and low toxicity. We isolated and purified rhamnolipids from Pseudomonas aeruginosa strain BS-161R, and these purified rhamnolipids were used to synthesize silver nanoparticles. The purified rhamnolipids were further characterized and the structure was elucidated based on one- and two-dimensional $^1H$ and $^{13}C$ NMR, FT-IR, and HR-MS spectral data. Purified rhamnolipids in a pseudoternary system of n-heptane and water system along with n-butanol as a cosurfactant were added to the aqueous solutions of silver nitrate and sodium borohydride to form reverse micelles. When these micelles were mixed, they resulted in the rapid formation of silver nanoparticles. The synthesized nanoparticles were characterized by UV-Visible spectroscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy (EDS). The nanoparticles formed had a sharp adsorption peak at 410 nm, which is characteristic of surface plasmon resonance of the silver nanoparticles. The nanoparticles were monodispersed, with an average particle size of 15.1 nm (${\sigma}={\pm}5.82$ nm), and spherical in shape. The EDS analysis revealed the presence of elemental silver signal in the synthesized nanoparticles. The formed silver nanoparticles exhibited good antibiotic activity against both Grampositive and Gram-negative pathogens and Candida albicans, suggesting their broad-spectrum antimicrobial activity.

• Journal of Electrochemical Science and Technology
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• 제14권1호
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• pp.15-20
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• 2023

Ionic liquids are considered as a promising, alternative solvent for the electrochemical synthesis of metals because of their high thermal and chemical stability, relatively high ionic conductivity, and wide electrochemical window. In particular, their wide electrochemical window enables the electrodeposition of metals without any side reaction of electrolytes such as hydrogen evolution. The electrodeposition of silver is conducted in 1-n-butyl-3-methylimidazolium chloride ([C4mim]Cl) ionic liquid system with a silver source of AgCl. This study is the first attempt to electrodeposit silver nanoparticles without using co-solvents other than [C4mim]Cl. Pulse electrolysis is employed for the synthesis of silver nanoparticles by varying applied potentials from -3.0 V to -4.5 V (vs. Pt-quasi reference electrode) and pulse duration from 0.1 s to 0.7 s. Accordingly, the silver nanoparticles whose size ranges from 15 nm to ~100 nm are obtained. The successful preparation of silver nanoparticles is demonstrated regardless of the kinds of substrate including aluminum, stainless steel, and carbon paper in the pulse electrolysis. Finally, the antimicrobial property of electrodeposited silver nanoparticles is confirmed by an antimicrobial test using Staphylococcus aureus.

• Mycobiology
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• 제39권1호
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• pp.26-32
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• 2011

Powdery mildew is one of the most devastating diseases in cucurbits. Crop yield can decline as the disease severity increases. In this study, we evaluated the effect of silver nanoparticles against powdery mildew under different cultivation conditions in vitro and in vivo. Silver nanoparticles (WA-CV-WA13B) at various concentrations were applied before and after disease outbreak in plants to determine antifungal activities. In the field tests, the application of 100 ppm silver nanoparticles showed the highest inhibition rate for both before and after the outbreak of disease on cucumbers and pumpkins. Also, the application of 100 ppm silver nanoparticles showed maximum inhibition for the growth of fungal hyphae and conidial germination in in vivo tests. Scanning electron microscope results indicated that the silver nanoparticles caused detrimental effects on both mycelial growth and conidial germination.

• Safety and Health at Work
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• 제2권1호
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• pp.34-38
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• 2011

Objectives: The antimicrobial activity of silver nanoparticles has resulted in their widespread use in many consumer products. Yet, despite their many advantages, it is also important to determine whether silver nanoparticles may represent a hazard to the environment and human health. Methods: Thus, to evaluate the genotoxic potential of silver nanoparticles, in vivo genotoxicity testing (OECD 474, in vivo micronuclei test) was conducted after exposing male and female Sprague-Dawley rats to silver nanoparticles by inhalation for 90 days according to OECD test guideline 413 (Subchronic Inhalation Toxicity: 90 Day Study) with a good laboratory practice system. The rats were exposed to silver nanoparticles (18 nm diameter) at concentrations of $0.7\;{\times}\;10^6$ particles/$cm^3$ (low dose), $1.4\;{\times}\;10^6$ particles/$cm^3$ (middle dose), and $2.9\;{\times}\;10^6$ particles/$cm^3$ (high dose) for 6 hr/day in an inhalation chamber for 90 days. The rats were killed 24 hr after the last administration, then the femurs were removed and the bone marrow collected and evaluated for micronucleus induction. Results: There were no statistically significant differences in the micronucleated polychromatic erythrocytes or in the ratio of polychromatic erythrocytes among the total erythrocytes after silver nanoparticle exposure when compared with the control. Conclusion: The present results suggest that exposure to silver nanoparticles by inhalation for 90 days does not induce genetic toxicity in male and female rat bone marrow in vivo.

• 멤브레인
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• 제29권5호
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• pp.246-251
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• 2019

올레핀/파라핀 분리를 위해 silver nanoparticle을 운반체로 이용하는 촉진수송막이 최근 많은 관심을 받고 있다. 기존 연구에서는 silver nanoparticle의 전구체로서 $AgBF_4$가 사용되어 왔다. 하지만 상대적으로 고가에 속하는 $AgBF_4$는 상업화에 적합하지 않기 때문에 비교적 저렴한 $AgClO_4$를 전구체로 이용해 제조된 silver nanopaticle를 활용해서 PEBAX-5513/AgNPs(전구체: $AgClO_4$)/7,7,8,8-tetracyanoquinodimethane (TCNQ) 복합막이 제조되었다. 그러나 여러 조성의 복합막이 제조되었으나 올레핀 분리성능은 관찰되지 않았다. FT-IR 분석 결과는 PEBAX-5513 고분자 내에서 silver nanoparticle이 형성되고 TCNQ에 의해 표면이 양극성화 되는 것을 확인하였지만 형성된 silver nanoparticle이 안정화 되지 못한 것으로 분석되었다. 이러한 결과들을 통해 은염 전구체의 음이온이 올레핀/파라핀 분리막에서 중요한 역할을 하는 것으로 판단되었다.

• Journal of the Optical Society of Korea
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• 제20권5호
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• pp.601-606
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• 2016

In this study, in order to analyze the low-temperature sintering process of silver and copper nanoparticles, we calculate their melting temperatures and surface melting temperatures with respect to particle size. For this calculation, we introduce the concept of mean-squared displacement of the atom proposed by Shi (1994). Using a parameter defined by the vibrational component of melting entropy, we readily obtained the surface and bulk melting temperatures of copper and silver nanoparticles. We also calculated the absorption cross-section of nanoparticles for variation in the wavelength of light. By using the calculated absorption cross-section of the nanoparticles at the melting temperature, we obtained the laser threshold energy for the sintering process with respect to particle size and wavelength of laser. We found that the absorption cross-section of silver nanoparticles has a resonant peak at a wavelength of close to 350 nm, yielding the lowest threshold energy. We calculated the intensity distribution around the nanoparticles using the finite-difference time-domain method and confirmed the resonant excitation of silver nanoparticles near the wavelength of the resonant peak.