• 펄프종이기술
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• 제46권4호
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• pp.28-36
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• 2014

We studied the green synthesis and antibacterial activity of paper coated with chitosan-silver (Ag) green nanocomposites for packaging applications. Green synthesis of Ag nanoparticles (AgNPs) was achieved by a chemical reaction involving a mixture of chitosan-silver nitrate ($AgNO_3$) in an autoclave at 15 psi, $121^{\circ}C$, for 30 min. AgNPs and their formation in chitosan was confirmed by UV-Vis spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS). As-prepared chitosan-AgNPs composite materials were coated on manila paper using Meyer rod. Surface morphology and Ag contents in coating layer were characterized by field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS). The mechanical properties such as tensile strength and elongation were significantly affected by coating with chitosan-AgNPs. The antibacterial test of coated paper was performed qualitatively and quantitatively against Escherichia coli (E. coli). It was shown to be effective in suppressing the growth of E. coli with increasing Ag contents on the surface of coated paper and more than 95 R (%) of antimicrobial rate was obtained at chitosan-AgNPs coated papers.

• 한국미생물·생명공학회지
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• 제39권1호
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• pp.77-85
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• 2011

본 연구는 은나노 입자의 항균활성을 알아보기 위하여, 그람 양성세균인 황색포도상구균과 그람 음성세균인 대장균에 대한 은나노 입자(Ag-NPs)를 처리 후, 세균세포 생장곡선측정, 활성산소생성능 측정, 세포질 단백질 누출량 측정, 젖산탈수소효소 활성측정 및 고분해능 임계방사 주사전자현미경 관찰이 수행되었다. 세균세포의 생장곡선 측정은 다양한 농도, 배양시간, 배양온도 및 pH에서 수행되었다. 결과적으로 황색 포도상구균과 대장균은 배양온도와 pH에 영향을 받지않고 은나노 입자에 의해 효과적으로 생장억제가 이루어지는 것을 관찰할 수 있었다. 또한 활성산소의 생성에 의하여 세포막의 파괴로 세포질내 물질의 유출을 세포질 유래 단백질 측정으로 확인할 수 있었으며, 젖산탈수소효소 활성측정을 통하여 은나노 입자에 대한 세포호흡억제활성 또한 확인할 수 있었다. 임계방사 주사전자현미경 관찰결과 은나노 입자에 의한 세균 세포표면의 형태학적 변화 또한 관찰되었다. 이러한 결과를 통하여 은나노 입자를 효과적인 항균활성소재로 활용 가능함이 입증되었다.

• 약학회지
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• 제56권6호
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• pp.382-389
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• 2012

Effects of citrate-capped silver nanoparticles (AgNPs) on the blood coagulation and platelet aggregation were investigated using whole blood, platelet rich plasma (PRP) and washed platelet obtained from SD male rats. To confirm the stability of AgNPs in the test, size distribution of the nanoparticles was measured in the vehicles including distilled water, serum, and platelet buffers. The average size of AgNPs was 20 nm in the vehicles, which means that the stability was maintained during the whole experimental period. When blood coagulation was monitored by using whole blood impedance aggregometer, coagulation was not observed at the concentration of 1, 10 and 50 ppm. Platelets in plasma or in buffer were not aggregated by AgNPs at the concentration of 1, 2 and 4 ppm, respectively. The test concentration of AgNPs could not be increased because the dark color of the nanoparticles impeded the transmission of light, which is an indicator of aggregation. Although the blood or platelets were pre-activated by collagen, thrombin, or ADP with sub-threshold level, aggregation was not observed at the test concentration. Microscopic observation also supported the result obtained by the aggregometer.

• Advances in nano research
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• 제5권4호
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• pp.373-392
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• 2017

Silver nanoparticles (AgNPs) were successfully synthesized through a simple green route using the Nelumbo nucifera leaf, stem and flower extracts. These nanoparticles showed characteristic UV-Vis absorption peaks between 410-450 nm which arises due to the plasmon resonance of silver nanoparticles. The Fourier transform infrared spectroscopy (FT-IR) confirmed the presence of amides and which acted as the stabilizing agent. X-ray diffraction spectrum of the nanoparticles confirmed the Face centered cubic (FCC) structure of the formed AgNPs. Dynamic light scattering technique was used to measure hydrodynamic diameter (68.6 nm to 88.1 nm) and zeta potential (-55.4 mV, -57.9 mV and 98.9 mV) of prepared AgNPs. The scanning electron micrographs of dislodged nanoparticles in aqueous solution showed the production of reasonably monodispersed silver nanoparticles (1-100 nm). The antimicrobial activity of prepared AgNPs was evaluated against fungi, Gram-positive and Gram-negative bacteria using disc diffusion method. Anti-corrosion studies were carried out using coupon method (mild steel and iron) and dye degradation studies were carried out by assessing photo-catalytic activity of Nelumbo nucifera extracts mediated AgNPs.

• Restorative Dentistry and Endodontics
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• 제46권3호
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• pp.38.1-38.13
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• 2021

The elimination of endodontic biofilms and the maintenance of a leak-proof canal filling are key aspects of successful root canal treatment. Several materials have been introduced to treat endodontic disease, although treatment success is limited by the features of the biomaterials used. Silver nanoparticles (AgNPs) have been increasingly considered in dental applications, especially endodontics, due to their high antimicrobial activity. For the present study, an electronic search was conducted using MEDLINE (PubMed), the Cochrane Central Register of Controlled Trials (CENTRAL), Google Scholar, and EMBASE. This review provides insights into the unique characteristics of AgNPs, including their chemical, physical, and antimicrobial properties; limitations; and potential uses. Various studies involving different application methods of AgNPs were carefully examined. Based on previous clinical studies, the synthesis, means of obtaining, usage conditions, and potential cytotoxicity of AgNPs were evaluated. The findings indicate that AgNPs are effective antimicrobial agents for the elimination of endodontic biofilms.

• Journal of the Optical Society of Korea
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• 제18권5호
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• pp.582-588
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• 2014

We study polarization-dependent spontaneous emission (SE) rate and light extraction efficiency (LEE) in localized-surface-plasmon (LSP)-coupled light emitting diodes (LEDs). The closely packed seven $Ag/SiO_2$ core-shell (CS) nanoparticles (NPs) lie on top of the GaN surface for LSP coupling with a radiated dipole. According to the dipole direction, both the SE rate and the LEE are significantly modified by the LSP effect at the $Ag/SiO_2$ CS NPs when the size of Ag, the thickness of $SiO_2$, and the position of the dipole source are varied. The enhancement of the SE rate is related to an induced dipole effect at the Ag, and the high LEE is caused by light scattering with an LSP mode at $Ag/SiO_2$ CS NPs. We suggest the optimum position of the quantum well (QW) in blue InGaN/GaN LEDs with $Ag/SiO_2$ CS NPs for practical application.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.493-493
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• 2014

The manufacturing cost of thin-film photovoltics can potentially be lowered by minimizing the amount of a semiconductor material used to fabricate devices. Thin-film solar cells are typically only a few micrometers thick, whereas crystalline silicon (c-Si) wafer solar cells are $180{\sim}300\mu}m$ thick. As such, thin-film layers do not fully absorb incident light and their energy conversion efficiency is lower compared with that of c-Si wafer solar cells. Therefore, effective light trapping is required to realize commercially viable thin-film cells, particularly for indirect-band-gap semiconductors such as c-Si. An emerging method for light trapping in thin film solar cells is the use of metallic nanostructures that support surface plasmons. Plasmon-enhanced light absorption is shown to increase the cell photocurrent in many types of solar cells, specifically, in c-Si thin-film solar cells and in poly-Si thin film solar cell. By proper engineering of these structures, light can be concentrated and coupled into a thin semiconductor layer to increase light absorption. In many cases, silver (Ag) nanoparticles (NP) are formed either on the front surface or on the rear surface on the cells. In case of poly-Si thin film solar cells, Ag NPs are formed on the rear surface of the cells due to longer wavelengths are not perfectly absorbed in the active layer on the first path. In our cells, shorter wavelengths typically 300~500 nm are also not effectively absorbed. For this reason, a new concept of plasmonic nanostructure which is NPs formed both the front - and the rear - surface is worth testing. In this simulation Al NPs were located onto glass because Al has much lower parasitic absorption than other metal NPs. In case of Ag NP, it features parasitic absorption in the optical frequency range. On the other hand, Al NP, which is non-resonant metal NP, is characterized with a higher density of conduction electrons, resulting in highly negative dielectric permittivity. It makes them more suitable for the forward scattering configuration. In addition to this, Ag NP is located on the rear surface of the cell. Ag NPs showed good performance enhancement when they are located on the rear surface of our cells. In this simulation, Al NPs are located on glass and Ag NP is located on the rear Si surface. The structure for the simulation is shown in figure 1. Figure 2 shows FDTD-simulated absorption graphs of the proposed and reference structures. In the simulation, the front of the cell has Al NPs with 70 nm radius and 12.5% coverage; and the rear of the cell has Ag NPs with 157 nm in radius and 41.5% coverage. Such a structure shows better light absorption in 300~550 nm than that of the reference cell without any NPs and the structure with Ag NP on rear only. Therefore, it can be expected that enhanced light absorption of the structure with Al NP on front at 300~550 nm can contribute to the photocurrent enhancement.

• 한국환경과학회지
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• 제29권12호
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• pp.1171-1184
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• 2020

The green synthesis of inorganic nanoparticles (NPs) using biomaterials has garnered considerable attention in recent years because of its eco-friendly, non-toxic, simple, and low-cost nature. In this study, we synthesized NPs of noble metals, such as Ag and Au using an aqueous extract of a marine seaweed, Ecklonia cava. The formation of AgNPs and AuNPs was confirmed by the presence of surface plasmon resonance peaks in UV-Vis absorption spectra at approximately 430 and 530 nm, respectively. Various properties of the NPs were evaluated using characterization techniques, such as dynamic light scattering, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. Phytochemicals in the seaweed extract, such as phlorotannins, acted as both reducing and stabilizing agents for the growth of the NPs. The green-synthesized AgNPs and AuNPs were found to exhibit high catalytic activity for the decomposition of organic dyes, including azo dyes, methylene blue, rhodamine B, and methyl orange.

• 한국분말재료학회지
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• 제21권3호
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• pp.179-184
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• 2014

In this study, we prepare polymer solar cells incorporating organic ligand-modified Ag nanoparticles (O-AgNPs) highly dispersed in the P3HT:PCBM layer. Ag nanoparticles decorated with water-dispersible ligands (WAgNPs) were also utilized as a control sample. The existence of the ligands on the Ag surface was confirmed by FT-IR spectra. Metal nanoparticles with different surface chemistries exhibited different dispersion tendencies. O-AgNPs were highly dispersed even at high concentrations, whereas W-AgNPs exhibited significant aggregation in the polymer layer. Both dispersion and blending concentration of the Ag nanoparticles in P3HT:PCBM matrix had critical effects on the device performance as well as light absorption. The significant changes in short-circuit current density ($J_{SC}$) of the solar cells seemed to be related to the change in the polymer morphology according to the concentration of AgNPs introduced. These findings suggested the importance of uniform dispersion of plasmonic metal nanoparticles and their blending concentration conditions in order to boost the solar cell performance.

• Bulletin of the Korean Chemical Society
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• 제32권10호
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• pp.3581-3586
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• 2011

Silver nanoparticle (Ag-NPs)-immobilized and amine-functionalized carbon nanotubes (MWCNTs), MWCNT-Ag-$NH_2$, were easily prepared in order to develop an efficient delivery system of biomolecules without complicated processes of manufacture. For this, Ag-NPs-immobilized MWCNTs, MWCNT-Ag, were initially prepared in order to create large surface area to enable more efficient linkage with guest-molecules using pristine MWCNTs. The Ag-NPs on MWCNTs were further positively functionalized with 2-aminoethanthiol to allow ionic linkage with biomolecules. Ultimately, the positively charged delivery system proved to be highly effective for the binding capacity of bovine serum albumin (BSA) as a negatively charged model protein, when compared to that of lysozyme used as a positively charged model protein. The releasing profile of BSA was observed in almost linear pattern for about two weeks in a saline solution. This study demonstrated the potential usefulness of the pristine MWCNTs in conjunction with Ag-NPs for the selective delivery of many (negatively or positively) charged biomolecules including proteins and genes.