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        검색결과 343

        141.
        2017.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        There has been much interest in recycling electronic wastes in order to mitigate environmental problems and to recover the large amount of constituent metals. Silver recovery from electronic waste is extensively studied because of environmental and economic benefits and the use of silver in fabricating nanodevices. Hydrometallurgical processing is often used for silver recovery because it has the advantages of low cost and ease of control. Research on synthesis recovered silver into nanoparticles is needed for application to transistors and solar cells. In this study, silver is selectively recovered from the by-product of electrodes. Silver precursors are prepared using the dissolution characteristics of the leaching solution. In the liquid reduction process, silver nanoparticles are synthesized under various surfactant conditions and then analyzed. The purity of the recovered silver is 99.24%, and the average particle size of the silver nanoparticles is 68 nm.
        4,000원
        142.
        2017.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study, magnetite (Fe3O4) nanoparticles were electrochemically synthesized in an aqueous electrolyte at a given potential of -1.3 V for 180 s. Scanning electron microscopy revealed that dendrite-like Fe3O4 nanoparticles with a mean size of < 80 nm were electrodeposited on a glassy carbon electrode (GCE). The Fe3O4/GCE was utilized for sensing chloramphenicol (CAP) by cyclic voltammetry and square wave voltammetry. A reduction peak of CAP at the Fe3O4/GCE was observed at 0.62 V, whereas the uncoated GCE exhibited a very small response compared to that of the Fe3O4/GCE. The electrocatalytic ability of Fe3O4 was mainly attributed to the formation of Fe(VI) during the anodic scan, and its reduction to Fe(III) on the cathodic scan facilitated the sensing of CAP. The effects of pH and scan rate were measured to determine the optimum conditions at which the Fe3O4/GCE exhibited the highest sensitivity with a lower detection limit. The reduction current for CAP was proportional to its concentration under optimized conditions in a range of 0.09-47 μM with a correlation coefficient of 0.9919 and a limit of detection of 0.09 μM (S/N=3). Moreover, the fabricated sensor exhibited anti-interference ability towards 4-nitrophenol, thiamphenicol, and 4-nitrobenzamide. The developed electrochemical sensor is a cost effective, reliable, and straightforward approach for the electrochemical determination of CAP in real time applications.
        4,000원
        145.
        2017.05 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Inorganic phosphors based on ZrO2:Eu3+ nanoparticles were synthesized by a salt-assisted ultrasonic spray pyrolysis process that is suitable for industrially-scalable production because of its continuous nature and because it does not require expensive precursors, long reaction time, physical templates or surfactant. This facile process results in the formation of tiny, highly crystalline spherical nanoparticles without hard agglomeration. The powder X-ray diffraction patterns of the ZrO2:Eu3+ (1-20 mol%) confirmed the body centered tetragonal phase. The average particle size, estimated from the Scherrer equation and from TEM images, was found to be approximately 11 nm. Photoluminescence (PL) emission was recorded under 266 nm excitation and shows an intense emission peak at 607 nm, along with other emission peaks at 580, 592 and 632 nm which are indicated in red.
        4,000원
        146.
        2017.04 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Through density functional theory calculations, to provide insight into the origins of the catalytic activity of Au nanoparticles (NPs) toward oxidation reactions, we have scrutinized the oxygen adsorption chemistry of 9 types of small unsupported Au NPs of around 1 nm in size (Au13, Au19, Au20, Au25, Au38, and Au55) looking at several factors (size, shape, and coordination number). We found that these NPs, except for the icosahedral Au13, do not strongly bind to O2 molecules. Energetically most feasible O2 adsorption that potentially provides high CO oxidation activity is observed in the icosahedral Au13, our smallest Au NP. In spite of the chemical inertness of bulk Au, the structural fluxionality of such very small Au NP enables strong O2 adsorption. Our results can support recent experimental findings that the exceptional catalytic activity of Au NPs comes from very small Au species consisting of around 10 atoms each.
        4,000원
        147.
        2017.04 구독 인증기관·개인회원 무료
        Starch is an abundant, renewable, and low cost material that has been extensively studied for its role in crystallization. The aim of this study is to develop a convenient and green approach to synthesize starch nanoparticles (StNPs). Short glucan chains were successfully prepared by using pullulanase that could debranch the amylopectin obtained from waxy maize starch. StNPs were prepared via the self-association of short glucan chains, of which the crystallinity structure changed from A-type (native starch) to B-type (starch nanoparticles) through the enzymatic hydrolysis and reassembly process at 4°C. Scanning electron microscopy (SEM), X-ray diffraction (XRD), dynamic light scattering (DLS) and differential scanning calorimetry (DSC) were used to characterize the morphology and crystalline structure of StNPs. The results showed that the diameter of StNPs ranged from 300 nm to 1.5 μm, depending on the initial concentration of short glucan chains and self-assembly time. The developed approach could produce well-defined and uniform starch nanoparticles that could readily be employed to encapsulate various functional guest molecules in biocompatible starch based nanoparticles in food industry.
        148.
        2017.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        4,000원
        149.
        2017.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        We have demonstrated the production of thin films containing multilayer graphene-coated copper nanoparticles (MGCNs) by a commercial electrodeposition method. The MGCNs were produced by electrical wire explosion, an easily applied technique for creating hybrid metal nanoparticles. The nanoparticles had average diameters of 10–120 nm and quasi-spherical morphologies. We made a complex-electrodeposited copper thin film (CETF) with a thickness of 4.8 μm by adding 300 ppm MGCNs to the electrolyte solution and performing electrodeposition. We measured the electric properties and performed corrosion testing of the CETF. Raman spectroscopy was used to measure the bonding characteristics and estimate the number of layers in the graphene films. The resistivity of the bare-electrodeposited copper thin film (BETF) was 2.092 × 10–6 Ω·cm, and the resistivity of the CETF after the addition of 300 ppm MGCNs was decreased by 2% to ~2.049 × 10–6 Ω·cm. The corrosion resistance of the BETF was 9.306 Ω, while that of the CETF was increased to 20.04 Ω. Therefore, the CETF with MGCNs can be used in interconnection circuits for printed circuit boards or semiconductor devices on the basis of its low resistivity and high corrosion resistance.
        4,000원
        150.
        2017.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study, simple chemical synthesis of green emitting Cd-free InP/ZnS QDs is accomplished by reacting In, P, Zn, and S precursors by one-pot process. The particle size and the optical properties were tailored, by controlling various experimental conditions, including [In]/[MA] (MA: myristic acid) mole ratio, reaction temperature and reaction time. The results of ultraviolet–visible spectroscopy (UV-vis), and of photoluminescence (PL), reveal that the exciton emission of InP was improved by surface coating, with a layer of ZnS. We report the correlation between each experimental condition and the luminescent properties of InP/ZnS core/shell QDs. Transmission electron microscopy (TEM), and X-ray powder diffraction (XRD) techniques were used to characterize the as-synthesized QDs. In contrast to core nanoparticles, InP/ZnS core/shell treated with surface coating shows a clear ultraviolet peak. Besides this work, we need to study what clearly determines the shell kinetic growth mechanism of InP/ZnS core shell QDs.
        4,000원
        151.
        2016.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The sol-gel method is the simplest method for synthesizing monodispersed silica particles. The purpose of this study is to synthesize uniform, monodisperse spherical silica nanoparticles using tetraethylorthosilicate (TEOS) as the silica precursor, ethanol, and deionized water in the presence of ammonia as a catalyst. The reaction time and temperature and the concentration of the reactants are controlled to investigate the effect of the reaction parameters on the size of the synthesized particles. The size and morphology of the obtained silica particles are investigated using transmission electron microscopy and particle size analysis. The results show that monodispersed silica particles over a size range of 54-504 nm are successfully synthesized by the sol-gel method without using any additional process. The nanosized silica particles can be synthesized at higher TEOS/H2O ratios, lower ammonia concentrations, and especially, higher reaction temperatures.
        4,000원
        152.
        2016.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Polyethersulfone (PES) 고분자 상변환막의 성능을 향상시키기 위해 PES 고분자에 나노 크기의 ZnO 무기입자를 함침시킨 혼합기질막(mixed matrix membrane)을 제조하고 특성을 평가하였다. PES-ZnO 혼합기질막은 ZnO 나노입자를 PES 대비 최대 0.375 wt%의 낮은 비율로 첨가시킨 PES-ZnO-NMP(N-methyl-1-pyrrolidone)로 이루어진 캐스팅 용액을 사용하여 상변환법을 통해 제조하였다. 제조된 혼합기질 막의 물성과 특성은 막의 단면구조 관찰, 접촉각 측정, 인장강도 측정, 순수 투과량 측정 및 BSA 단백질 용액의 한외여과 실험을 통해 평가하였다. 이 결과 혼합기질 막은 PES 고분자 matrix에 함유된 ZnO 나노입자로 인해 막의 친수성이 증가하여 막오염 발생이 억제되어 투과량이 증가하였다. ZnO 나노입자는 혼합기질막의 제조에 있어 막오염의 발생 억제와 투과량 증가에 유용하게 사용될 수 있는 무기물 첨가제임을 알 수 있다.
        4,000원
        153.
        2016.11 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Ni nanoparticles (NPs)-graphitic carbon nanofiber (GCNF) composites were fabricated using an electrospinning method. The amounts of Ni precursor used as catalyst for the catalytic graphitization were controlled at 0, 2, 5, and 8 wt% to improve the photovoltaic performances of the nanoparticles and make them suitable for use as counter electrodes for dyesensitized solar cells (DSSCs). As a result, Ni NPs-GCNF composites that were fabricated with 8 wt% Ni precursors showed a high circuit voltage (0.73 V), high photocurrent density (14.26 mA/cm2), and superb power-conversion efficiency (6.72 %) when compared to those characteristics of other samples. These performance improvements can be attributed to the reduced charge transport resistance that results from the synergetic effect of the superior catalytic activity of Ni NPs and the efficient charge transfer due to the formation of GCNF with high electrical conductivity. Thus, Ni NPs-GCNF composites may be used as promising counter electrodes in DSSCs.
        4,000원
        154.
        2016.11 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Ni nanoparticles (NPs)-graphitic carbon nanofiber (GCNF) composites were fabricated using an electrospinning method. The amounts of Ni precursor used as catalyst for the catalytic graphitization were controlled at 0, 2, 5, and 8 wt% to improve the photovoltaic performances of the nanoparticles and make them suitable for use as counter electrodes for dyesensitized solar cells (DSSCs). As a result, Ni NPs-GCNF composites that were fabricated with 8 wt% Ni precursors showed a high circuit voltage (0.73 V), high photocurrent density (14.26 mA/cm2), and superb power-conversion efficiency (6.72 %) when compared to those characteristics of other samples. These performance improvements can be attributed to the reduced charge transport resistance that results from the synergetic effect of the superior catalytic activity of Ni NPs and the efficient charge transfer due to the formation of GCNF with high electrical conductivity. Thus, Ni NPs-GCNF composites may be used as promising counter electrodes in DSSCs.
        4,000원
        155.
        2016.11 구독 인증기관·개인회원 무료
        PEBAX®는 폴리에테르가 우수한 CO2용해도를 나타내어 기체분리막의 소재로 주목받고 있지만 폴리아마이드의 crystallinity로 인해 투과성능면에서 제약을 받는다고 알려져 있다. 본 연구에서는 PEBAX® 막의 기체투과특성을 향상시키기 위해 합성된 aluminosilicate hollow nanoparticles를 막 내부에 고르게 분산시켜 함량별로 혼합막을 제조한다. 분산된 나노입자의 함량에 따른 CO2 용해도 증가, 확산 속도의 증가로 인하여 선택도와 투과도의 향상을 예측할 수 있다. 첨가된 나노입자의 morphology와 yield를 확인하고, 첨가량이 증가할수록 선택도의 변동없이 투과도가 증가하는 것을 알 수 있다.
        156.
        2016.11 구독 인증기관·개인회원 무료
        Facilitated transport membranes in the solid state have been attractive because they can improve both the permeability and the selectivity simultaneously to overcome the trade-off behavior. The carrier activity for facilitated transport plays a key role in determining separation performance. We have reported the solid-state facilitated transport membranes containing surface-activated Ag nanoparticles (NPs) as an olefin carrier for separation of olefin/paraffin mixtures, particularly propylene/propane mixture. Interestingly, the surface positive charge density of Ag atom in Ag NPs was linearly correlated with the propylene solubility and also with the propylene/propane selectivity. In addition, the separation performance has been maintained unchanged up to 500 hours.
        157.
        2016.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Noncontact direct-printed conductive silver patterns with an enhanced electrical resistivity are fabricated using a silver ink with a mixture of silver nanoparticles and nanoplates. The microstructure and electrical resistivity of the silver pattern are systematically investigated as a function of the mixing ratio of the nanoparticles and nanoplates. The pattern, which is fabricated using a mixture with a mixing ratio of 3(nanoparticles):7(nanoplates) and sintered at 200oC shows a highly dense and well-sintered microstructure and has a resistivity of 7.60 μΩ·cm. This originates a mutual synergistic effect through a combination of the sinterability of the nanoparticles and the packing ability of the nanoplates. This is a conductive material that can be used to fabricate noncontact direct-printed conductive patterns with excellent electrical conductivity for various flexible electronics applications, including solar cells, displays, RFIDs, and sensors.
        4,000원
        159.
        2016.10 구독 인증기관·개인회원 무료
        Soybean peptide (SP) exhibited low intestinal absorption at oral administration due to its fragile structure under gastric digestion. Therefore, we have attempted to encapsulate peptide by cross-linkage interaction between positive charged chitosan (CS) or chitosan oligosaccharide (CSO) and negative charged peptide. The CS (or CSO) with SP nanoparticles were prepared by using ultrasonification technique. The objective of this study was to find the optimal processing method by changing concentration, pH, and homogenizing conditions. We measured physicochemical properties such as particle size, zeta-potential, encapsulation efficiency (EE%), release rate (RR) and antioxidant ability of samples. The results showed that the optimal processing method was using 0.5% (w/v) CSO (diluted by pH 3 Acetic acid buffer) mixed with 0.5% (w/v) SP (diluted by pH 6 buffer) by 9:1 ratio. Afterwards, using high-speed mixer at 12,000 rpm for 3 min, and then passed 2 times through an ultrasonicator (50% power, 3 min). In this way for processing, the particle sizes of CSO/SP nanoparticles were approximately 300 nm, zeta-potential were approximately 45 mV. In addition, the EE% and RR of CS/SP nanoparticles was higher than the CSO/SP nanoparticles. The increase in antioxidant ability of SP was attributed to the affected by CS/CSO microcapsules. In conclusion, this research can befoundation for the manufacturing process of CS/SP nanoparticles, and it was expected that the future application of this nanoparticle in food matrix.
        160.
        2016.10 구독 인증기관·개인회원 무료
        A novel nanocomposite LDPE film with UV protective properties was developed for active packaging applications. Initially, undoped and Mn-doped TiO2 nanoparticles (NPs) were synthesized by the sol-gel method and the resulting particles were characterized. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed an agglomerated nature and spherical morphology. X-ray diffraction (XRD) studies indicated that all products were crystalline and in the form of rutile. The reflectance spectrum of undoped TiO2 NPs demonstrated a characteristic sharp edge at 410 nm. Subsequently, nanocomposite (NC) LDPE samples were prepared with the NPs by solvent precipitation followed by film casting. The optical and thermal properties of the NC samples were investigated. Incremental increases in Mn concentration from 0.25 mol % to 1.00 mol % were associated with progressive decreases in light transmission in the UV region. The melting and maximum decomposition temperatures of all NCs were 107 and 442-449 °C, respectively. The UV protective LDPE-based NC films exhibited superior photostability. Absorption in the FTIR spectra at 1716 and 1734 cm-1 changed after 4-wk exposure to UV for all film samples as a consequence of photodegradation. Finally, the photooxidation of perilla oil was assessed as an example of a UV protective packaging application. After 12 days, protection with 1.00 mol% Mn-doped TiO2-LDPE was associated with a gradual increase in PV, while protection with TiO2-LDPE was associated with a significant increase and protection with the control treatment was associated with a dramatic increase in PV. Hence, a 1.00 mol% Mn-doped TiO2-LDPE NC showed promise for UV shielding packaging applications.