• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.636-636
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• 2013

Since first discovery of strong Raman spectrum of molecules adsorbed on rough noble metal, surface enhanced Raman scattering (SERS) has been widely used for detection of molecules with low concentration. Surface plasmons at noble metal can enhance Raman spectrum and using Au nanostructures as substrates of SERS has advantages due to it has chemical stability and biocompatibility. However, the photoluminescence (PL) background from Au remains a problem because of obtaining molecular vibration information. Recently, graphene, two-dimensional atomic layer of carbon atoms, is also well known as PL quenchers for electronic and vibrational excitation. In this study, we observed SERS of single layer graphene on or under monolayer of Au nanoparticles (NPs). Single layer graphene is grown by chemical vapor deposition and transferred onto or under the monolayer of Au NPs by using PMMA transfer method. Monolayer of Au NPs prepared using Langmuir-Blodgett method on or under graphene surface provides closed and well-packed monolayer of Au NPs. Scanning electron microscopy (SEM) and Raman spectroscopy (WItec, 532 nm) were performed in order to confirm effects of Au NPs on enhanced Raman spectrum. Highly enhanced Raman signal of graphene by Au NPs were observed due to many hot-spots at gap of closed well-packed Au NPs. The results showed that single layer graphene provides larger SERS effects compared to multilayer graphene and the enhancement of the G band was larger than that of 2D band. Moreover, we confirm the appearance of D band in this study that is not clear in normal Raman spectrum. In our study, D band appearance is ascribed to the SERS effect resulted from defects induced graphene on Au NPs. Monolayer film of Au NPs under the graphene provided more highly enhanced graphene Raman signal compared to that on the graphene. The Au NPs-graphene SERS substrate can be possibly applied to biochemical sensing applications requiring highly sensitive and selective assays.

• 상하수도학회지
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• 제27권5호
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• pp.571-579
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• 2013

The aggregation behaviors of silver nanoparticles (AgNPs) and titanium dioxide ($TiO_2$) nanoparticles were investigated. Time-resolved dynamic light scattering (DLS) was used to study the initial aggregation of AgNPs and $TiO_2$ over a range of mono (NaCl) and divalent ($CaCl_2$) electrolyte concentrations. The effects of pH, initial concentration of NPs and natural organic matters (NOM) on the aggregation of NPs were also investigated. The aggregation of both nanoparticles showed classical Derjaguin-Landau-Verwey-Overbeek (DLVO) type behavior. Divalent electrolyte was more efficient in destabilize the AgNPs and $TiO_2$ than monovalent electrolyte. The effect of pH on the aggregation of AgNPs was not significant. But the aggregation rate of $TiO_2$ was much higher with increasing pH. Higher NPs concentration leads to faster aggregation. Natural organic matter (NOM) was found to substantially hinder the aggregation of both AgNPs and $TiO_2$. This study found that the aggregation behavior of AgNPs and $TiO_2$ are closely associated with environmental factors such as ionic strength, pH, initial concentration of NPs and NOM.

• Journal of Microbiology and Biotechnology
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• 제31권12호
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• pp.1656-1666
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• 2021

Dental pathogens lead to chronic diseases like periodontitis, which causes loss of teeth. Here, we examined the plausible antibacterial efficacy of copper nanoparticles (CuNPs) synthesized using Cupressus macrocarpa extract (CME) against periodontitis-causing bacteria. The antimicrobial properties of CME-CuNPs were then assessed against oral microbes (M. luteus. B. subtilis, P. aerioginosa) that cause periodontal disease and were identified using morphological/ biochemical analysis, and 16S-rRNA techniques. The CME-CuNPs were characterized, and accordingly, the peak found at 577 nm using UV-Vis spectrometer showed the formation of stable CME-CuNPs. Also, the results revealed the formation of spherical and oblong monodispersed CME-CuNPs with sizes ranged from 11.3 to 22.4 nm. The FTIR analysis suggested that the CME contains reducing agents that consequently had a role in Cu reduction and CME-CuNP formation. Furthermore, the CME-CuNPs exhibited potent antimicrobial efficacy against different isolates which was superior to the reported values in literature. The antibacterial efficacy of CME-CuNPs on oral bacteria was compared to the synergistic solution of clindamycin with CME-CuNPs. The solution exhibited a superior capacity to prevent bacterial growth. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and fractional inhibitory concentration (FIC) of CME-CuNPs with clindamycin recorded against the selected periodontal disease-causing microorganisms were observed between the range of 2.6-3.6 ㎍/ml, 4-5 ㎍/ml and 0.312-0.5, respectively. Finally, the synergistic antimicrobial efficacy exhibited by CME-CuNPs with clindamycin against the tested strains could be useful for the future development of more effective treatments to control dental diseases.

• Korean Chemical Engineering Research
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• 제61권1호
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• pp.52-57
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• 2023

본 연구는 고성능 유연 전극 소재 개발을 위한 기초 연구로, 유연 전극 소재의 성능을 향상시키기 위해 금속 산화물 CuO nanoparticles (CuO NPs)를 도입하여 탄소나노튜브 섬유(carbon nanotube fiber; CNT fiber) 표면 위에 전기화학적 증착시켜 CNT fiber/CuO NPs 전극을 합성하고, 이를 전기화학적 비효소 글루코스 센서에 적용하였다. 이 전극의 표면 및 elemental composition 분석은 주사전자 현미경(SEM)과 에너지분산형 분광분석법(EDS)을 이용하였으며, 전극의 전기화학적 특성 및 글루코스에 대한 센싱 성능은 순환전압 전류법(CV)과 전기화학 임피던스법(EIS), 시간대전류법(CA)을 통해 조사되었다. CNT fiber/CuO NPs 전극은 CNT fiber의 우수한 특성과 함께 CuO NPs 도입에 따른 약 2.6배의 유효 전극면적(active surface area) 증가 효과와 11배 정도의 향상된 전자전달(electron transfer) 특성 및 우수한 전기적 촉매 활성(electrocatalytic activity) 덕분에 CNT fiber 유연 기반 전극의 글루코스 검출에 대한 성능이 개선되었다. 따라서, 본 연구를 기반으로 다양한 나노구조체를 활용한 고성능 유연 전극 소재 개발이 기대된다.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2592-2596
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• 2012

Cysteine capped silver nanoparticles (Cys-AgNPs) have been synthesized by employing electrochemically active biofilm (EAB), $AgNO_3$ as precursor and sodium acetate as electron donor in aqueous solution at $30^{\circ}C$. Cys-AgNPs of 5-10 nm were synthesized and characterized by UV-Vis, FT-IR, XRD and TEM. Capping of the silver nanoparticles with cysteine provides stability to nanoparticles by a thiolate bond between the amino acid and the nanoparticle surface and hydrogen bonding among the Cys-AgNPs. In addition, the antibacterial effects of as-synthesized Cys-AgNPs have been tested against two pathogenic bacteria Escherichia coli (O157:H7) and Pseudomonas aeruginosa (PAO1). The results demonstrate that the as-synthesized Cys-AgNPs can proficiently inhibit the growth and multiplication of E. coli and P. aeruginosa.

• Bulletin of the Korean Chemical Society
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• 제32권4호
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• pp.1133-1137
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• 2011

Ordered array of gold nanoparticles (Au NPs) over ITO glass was investigated in terms of ITO pretreatment, particle size, and diamines with different chain length. Owing to the indium-tin-oxide (ITO) layer coated on the glass, the substrate surface has a limited number of hydroxyl groups which can produce functionalized amine groups for Au binding, which resulted in the loosely-packed array of Au NPs on the ITO surface. Diamine ligand as a molecular linker was introduced to enhance the lateral binding of adjacent Au NPs immobilized on the amine-functionalized ITO glass, consequently leading to the densely-packed array of Au NPs over the ITO substrate. The molecular bridging effect was strengthened with the increase of chain length of diamines: C-12 > C-8. The packing density of small Au NPs (< 40 nm) was significantly increased with the increase of C-8 diamine, but large Au NPs (> 60 nm) did not produce densely-packed array on the ITO glass even for the dosage of C-12 diamine.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.105.1-105.1
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• 2011

To enhance the performance of photovoltaic a-Si:H solar cells with a hybrid-type light absorbing structure of single crystal silicon nanoparticles (Si NPs) in a-Si:H matrix, single crystal Si NPs were produced by laser pyrolysis. The Si NPs were synthesized by $SiH_4$ gas decomposition using a $CO_2$ laser. The properties of Si NPs were controlled by process parameters such as $CO_2$ laser power, reactive gas pressure, and $H_2/SiH_4$ gas flows. The crystalline properties and sizes of Si NPs were analyzed by High Resolution Transmission Electron Microscopy (HRTEM). The sizes of Si NPs were controllable in the range of 5-15 nm in diameter and the effects of process parameters of laser pyrolysis were systematically investigated.

• Bulletin of the Korean Chemical Society
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• 제35권8호
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• pp.2251-2256
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• 2014

We have successfully decorated reduced graphene oxide (RGO) with silver nanoparticles (AgNPs) by microwaving silver alkylcarbamate for 13 seconds using 1-amino-4-methylpiperazine. Uniform AgNPs (20-40 nm) were effectively prepared, and 1-amino-4-methylpiperazine acted as a reaction medium, reducing agent, and stabilizer. Particle size and morphology were correlated with the silver alkylcarbamate concentration and microwave time. The graphene/AgNPs composites were characterized by Raman, X-ray diffraction, and scanning electron microscopy to confirm that the AgNPs were uniformly decorated onto the graphene. Measurements of the transparent conductive property at room temperature indicated that these graphene/AgNPs nanosheets with 55.45% transmittance were electrically continuous with a sheet resistance of approximately $43{\Omega}/{\Box}$.

• 한국물환경학회지
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• 제23권4호
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• pp.429-433
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• 2007

Many researchers have made a study of NPS unit-loads and the scientific evaluation method which need for formulating and enforcing a Total Maximum Daily Load (TMDL) management system and modifying a pollutant discharge loadings function. Some showed the event mean concentration (EMC) on single land-use. For the most parts, as the results showed on multiple land-uses, those cannot be used for NPS unit-loads calculation. NPS runoff shows various phenomena depending on rainfall monitoring data, therefore sampling methods and frequency for NPS monitoring must be different from the general monitoring for water quality trend assessment.

• 대한화학회지
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• 제66권4호
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• pp.284-297
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• 2022

The antibacterial activity of metallic nanoparticles (NPs), especially silver (Ag), has been investigated during the course of time in various chemical reactions for antibiotics free agents. Green synthesis of metallic NPs using either microorganisms or plant-extracts has appeared as a simple and replacement to chemical and physical methods. The synthesizing of these NPs through ecofriendly methods signifies an exceedingly applicable approach for offering economical, preferring scalability and possessing negligible ecological influences. Essential-oils are among the subordinate metabolites of plants and their antibacterial anti-inflammatory characteristics have been investigated widely and are commonly attained from the aromatic plants. The usage of essential-oils as reducing agents in biosynthesizing of Ag NPs bring together the interaction of a vital antibacterial agent that simplify the nucleation and growth process within the NPs formation. This review article is offering a progressive process of Ag NPs synthesis using essential oils along with proposing the most applicable formation mechanisms and their antibacterial activities.