In this study, we synthesize silica-core gold-satellite nanoparticles (SGNPs) for the surface-enhanced Raman scattering (SERS) based sensing applications. They consist of gold satellite nanoparticles (AuNPs) fixed on the silica core nanoparticles, which sizes of AuNPs can be tunned by varying the amount of reactants (growth solution and reducing agent). Their surface plasmon resonance (SPR) properties were characterized by using UV-vis spectroscopy, showing that the growth of AuNPs on silica cores leads to the light absorption in the longer wavelength region. Furthermore, the size increase of AuNPs exhibited the dramatic change in SERS activity due to the formation of hot spots. The optimized SGNPs showing enhancement factor ~3.8x106 exhibited a detection limit of rhodamine 6G (R6G) as low as 10-8M. These findings suggest the importance of size control of SGNPs and their SPR properties to develop highly efficient SERS sensors.

To synthesize Sn nanoparticles (NPs) less than 30 nm in diameter, a modified polyol process was conducted at room temperature using a reducing agent, and the effects of different pH values of the initial solutions on the morphology and size of the synthesized Sn NPs were analyzed. tin(II) 2-ethylhexanoate, diethylene glycol, sodium borohydride, polyvinyl pyrrolidone (PVP), and sodium hydroxide were used as a precursor, reaction medium, reducing agent, capping agent, and pH adjusting agent, respectively. It was found by transmission electron microscopy that the morphology of the synthesized Sn NPs varied according to the pH of the initial solution. Moreover, while the size decreased to 11.32 nm with an increase up to 11.66 of the pH value, the size increased rapidly to 39.25 nm with an increase to 12.69. The pH increase up to 11.66 dominantly promoted generation of electrons and increased the amount of initial nucleation in the solution, finally inducing the reduced-size of the Sn particles. However, the additional increase of pH dominantly induced a decrease of PVP by neutralization, which resulted in acceleration of the agglomeration by collisions between particles.

In this study, we investigated localized surface plasmon resonance and the related coupling phenomena with respect to various geometric parameters of Ag nanoparticles, including the size and inter-particle distance. The plasmon resonances of Ag nanoparticles were studied using three-dimensional finite difference time domain(FDTD) calculations. From the FDTD calculations, we discovered the existence of a symmetric and an anti-symmetric plasmon coupling modes in the coupled Ag nanoparticles. The dependence of the resonance wavelength with respect to the inter-particle distance was also investigated, revealing that the anti-symmetric mode is more closely correlated with the inter-particle distance of the Ag nanoparticles than the symmetric mode. We also found that higher order resonance modes are appeared in the extinction spectrum for closely spaced Ag nanoparticles. Plasmon resonance calculations for the Ag particles coated with a SiO2 layer showed enhanced plasmon coupling due to the strengthened plasmon resonance, suggesting that the inter-particle distance of the Ag nanoparticles can be estimated by measuring the transmission and absorption spectra with the plasmon resonance of symmetric and anti-symmetric localized surface plasmons.

Inorganic pigments have high thermal stability and chemical resistance at high temperature. For these reasons, they are used in clay, paints, plastic, polymers, colored glass and ceramics. CoAl2O4 nano-powder was synthesized by reverse-micelle processing the mixed precursor(consisting of Co(NO3)2 and Al(NO3)3). The CoAl2O4 was prepared by mixing an aqueous solution at a Co:Al molar ratio of 1:2. The average particle size, and the particle-size distribution, of the powders synthesized by heat treatment (at 900; 1,000; 1,100; and 1,200˚C for 2h) were in the range of 10-20 nm and narrow, respectively. The average size of the synthesized nano-particles increased with increasing water-to-surfactant molar ratio. The synthesized CoAl2O4 powders were characterized by X-ray diffraction analysis(XRD), field-emission scanning electron microscopy(FE-SEM) and color spectrophotometry. The intensity of X-ray diffraction of the synthesized CoAl2O4 powder, increased with increasing heating temperature. As the heating temperature increased, crystal-size of the synthesized powder particles increased. As the R-value(water/surfactant) and heating temperature increased, the color of the inorganic pigments changed from dark blue-green to cerulean blue.

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 (W-AgNPs) 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-AgNPswere highly dispersed even at high concentrations, whereas W-AgNPs exhibited significant aggregation in the polymerlayer. Both dispersion and blending concentration of the Ag nanoparticles in P3HT:PCBM matrix had critical effects onthe device performance as well as light absorption. The significant changes in short-circuit current density (JSC) of thesolar cells seemed to be related to the change in the polymer morphology according to the concentration of AgNPsintroduced. These findings suggested the importance of uniform dispersion of plasmonic metal nanoparticles and theirblending concentration conditions in order to boost the solar cell performance.

Purpose: Various studies have been conducted on macromolecular materials that not only have basic characteristics but also UV-blocking capabilities. Here we report tinted hydrogel contact lens containing titanium silicon oxide nanoparticles. This study also showed the physical and optical effects of 4-iodoaniline on contact lenses, which affect UV transmissibility. Methods: Titanium silicon oxide nanoparticles were used as additives. HEMA, MA, MMA, 4-iodoaniline and a cross-linker EGDMA were copolymerized in the presence of AIBN as an initiator. The physical properties such as water content, refractive index, contact angle, spectral transmittance of produced contact lenses were measured. Results: Measurement of the physical characteristics of the copolymerized material showed the water content of 38.68~35.01%, refractive index of 1.4350~1.4418, contact angel of 34.15~57.25° and spectral transmittance of 1.0~84.8%. Also, the transmittance for UV light was reduced significantly in combinations containing titanium silicon oxide nanoparticles. Conclusions: Tinted hydrogel contact lens material containing titanium silicon oxide nanoparticles is expected to be able to be used usefully as a material for UV-block hydrogel contact lens.

In order to fabricate the porous Al₂O₃ with dispersion of nano-sized Cu particles, freeze-drying of cam-phene/Al₂O₃ slurry and solution chemistry process using Cu-nitrate are introduced. Camphene slurries with 10vol% Al₂O₃ was frozen at -25˚C. Pores were generated by sublimation of the camphene during drying in air. The sinteredsamples at 1400 and 1500oC showed the same size of large pores which were aligned parallel to the sublimable vehiclesgrowth direction. However, the size of fine pores in the internal walls of large pores decreased with increase in sinteringtemperature. It was shown that Cu particles with the size of 100 nm were homogeneously dispersed on the surfaces ofthe large pores. Antibacterial test using fungus revealed that the porous Al₂O₃/1vol% Cu composite showed antifungalproperty due to the dispersion of Cu particles. The results are suggested that the porous composites with required porecharacteristics and functional property can be fabricated by freeze-drying process and addition of functional nano par-ticles by chemical method.

In the present work, WO3 and WO3-TiO2 were prepared by the chemical deposition method. Structural variations, surface state and elemental compositions were investigated for preparation of WO3-TiO2 sonocatalyst. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and transmission electron microscopy (TEM) were employed for characterization of these new photocatalysts. A rhodamine B (Rh.B) solution under ultrasonic irradiation was used to determine the catalytic activity. Excellent catalytic degradation of an Rh.B solution was observed using the WO3-TiO2 composites under ultrasonic irradiation. Sonocatalytic degradation is a novel technology of treating wastewater. During the ultrasonic treatment of aqueous solutions sonoluminescence, cavitaties and "hot spot" occurred, leading to the dissociation of water molecules. In case of a WO3 coupled system, a semiconductor coupled with two components has a beneficial role in improving charge separation and enhancing TiO2 response to ultrasonic radiations. In case of the addition of WO3 as new matter, the excited electrons from the WO3 particles are quickly transferred to TiO2 particle, as the conduction band of WO3 is 0.74 eV which is -0.5 eV more than that of TiO2. This transfer of charge should enhance the oxidation of the adsorbed organic substrate. The result shows that the photocatalytic performance of TiO2 nanoparticles was improved by loading WO3.

Well-distributed ruthenium (Ru) nanoparticles decorated on porous carbon nanofibers (CNFs) were synthesized using an electrospinning method and a reduction method for use in high-performance elctrochemical capacitors. The formation mechanisms including structural, morphological, and chemical bonding properties are demonstrated by means of field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). To investigate the optimum amount of the Ru nanoparticles decorated on the porous CNFs, we controlled three different weight ratios (0 wt%, 20 wt%, and 40 wt%) of the Ru nanoparticles on the porous CNFs. For the case of 20 wt% Ru nanoparticles decorated on the porous CNFs, TEM results indicate that the Ru nanoparticles with ~2-4 nm size are uniformly distributed on the porous CNFs. In addition, 40 wt% Ru nanoparticles decorated on the porous CNFs exhibit agglomerated Ru nanoparticles, which causes low performance of electrodes in electrochemical capacitors. Thus, proper distribution of 20 wt% Ru nanoparticles decorated on the porous CNFs presents superior specific capacitance (~280.5 F/g at 10 mV/s) as compared to the 40 wt% Ru nanoparticles decorated on the porous CNFs and the only porous CNFs. This enhancement can be attributed to the synergistic effects of well-distributed Ru nanoparticles and porous CNF supports having high surface area.

목적: 본 연구는 콘택트렌즈 재료로 널리 사용되는 2-hydroxyethyl methacrylate, N-vinyl-2-pyrrolidone, methyl methacrylate, ethylene glycol dimethacrylate에 titanium isopropoxide와 tungsten(VI) oxide 나노입자를 첨가하여 안의료용 렌즈 재료를 중합하였다. 방법: 안의료용 콘택트렌즈의 첨가제로 Tungsten (VI) oxide 나노입자 사용의 활용도를 조사하기 위해 tungsten(VI) oxide 나노입자를 포함한 하이드로젤 콘택트렌즈 재료의 광학적, 물리적 특성 변화를 측정하였다. 결과: 생성된 고분자에 대한 자외선 영역의 투과율은 매우 낮게 측정되어 자외선 차단 능력이 있는 것으로 나타났다. 또한 tungsten(VI) oxide 나노입자의 첨가는 함수율의 큰 변화를 나타내지 않았으나 일정비율을 첨가한 조합에서는 소량의 함수율 변화가 나타났다. 함수율의 큰 변화가 없음에도 불구하고 산소침투율의 측정 값은 tungsten(VI) oxide 나노입자의 첨가 비율이 증가할수록 계속적으로 감소하는 경향이 나타 났다. 결론: 이상의 결과를 통해 titanium isopropoxide 및 tungsten(VI) oxide 나노입자는 하이드로젤 콘택트렌즈의 기본적인 물성을 만족시키면서 기능성 콘택트렌즈 재료로 유용하게 활용될 수 있을 것으로 판단된다.

We demonstrated size control of Au nanoparticles by heat treatment and their use as a catalyst for single-walled carbon nanotube (SWNTs) growth with narrow size distribution. We used uniformly sized Au nanoparticles from commercial Au colloid, and intentionally decreased their size through heat treatment at 800 oC under atmospheric Ar ambient. ST-cut quartz wafers were used as growth substrates to achieve parallel alignment of the SWNTs and to investigate the size relationship between Au nanoparticles and SWNTs. After the SWNTs were grown via chemical vapor deposition using methane gas, it was found that a high degree of horizontal alignment can be obtained when the particle density is low enough to produce individual SWNTs. The diameter of the Au nanoparticles gradually decreased from 3.8 to 2.9 nm, and the mean diameter of the SWNTs also changed from 1.6 to 1.2 nm for without and 60 min heat treatment, respectively. Raman results reconfirmed that the prolonged heat treatment of nanoparticles yields thinner tubes with narrower size distribution. This work demonstrated that heat treatment can be a straightforward and reliable method to control the size of catalytic nanoparticles and SWNT diameter.

To understand how reactivity between reinforcing nanoparticles and aqueous solution affects electrodeposited Cu thin films, two types of commercialized cerium oxide (ceria, CeO2) nanoparticles were used with copper sulfate electrolyte to form in-situ nanocomposite films. During this process, we observed variation in colors and pH of the electrolyte depending on the manufacturer. Ceria aqueous solution and nickel sulfate (NiSO4) aqueous solutions were also used for comparison. We checked several parameters which could be key factors contributing to the changes, such as the oxidation number of Cu, chemical impurities of ceria nanoparticles, and so on. Oxidation number was checked by salt formation by chemical reaction between CuSO4 solution and sodium hydroxide (NaOH) solution. We observed that the color changed when H2SO4 was added to the CuSO4 solution. The same effect was obtained when H2SO4 was mixed with ceria solution; the color of ceria solution changed from white to yellow. However, the color of NiSO4 solution did not show any significant changes. We did observe slight changes in the pH of the solutions in this study. We did not obtain firm evidence to explain the changes observed in this study, but changes in the color of the electrolyte might be caused by interaction of Cu ion and the by-product of ceria. The mechanical properties of the films were examined by nanoindentation, and reaction between ceria and electrolyte presumably affect the mechanical properties of electrodeposited copper films. We also examined their crystal structures and optical properties by X-ray diffraction (XRD) and UV-Vis spectroscopy.

Nanocomposites comprised of graphene oxide (GO) nanosheets and magnesium oxide (MgO) nanoparticles were synthesized by a sol-gel process. The synthesized samples were studied by X-ray powder diffraction, atomic force microscopy, transmission electron microscopy, and energy-dispersive X-ray analysis. The results show that the MgO nanoparticles, with an average diameter of 70 nm, are decorated uniformly on the surface of the GOs. By controlling the concentration of the MgO precursors and reaction cycles, it was possible to control the loading density and the size of the resulting MgO particles. Because the MgO particles are robustly anchored on the GO structure, the MgO/GOs nanocomposites will have future applications in the fields of adsorption and chemical sensing.

ZnO nanoparticles in the size range from 5 to 15 nm were prepared by zinc-lithium-acetate system. The morphologies and structures of ZnO were characterized by TEM, XRD and FT-IR spectra. UV-visible results shows that the absorption of ZnO nanoparticles is blue shifted with decrease in particles size. Furthermore, photoluminescence spectra of the ZnO nanoparticles were also investigated. The ZnO nanoparticles have strong visible-emission intensity and their intensities depend upon size of ZnO nanoparticles.

In order to produce size-controllable Ag nanoparticles and a nanomesh-patterned Si substrate, we introduce a rapid thermal annealing(RTA) method and a metal assisted chemical etching(MCE) process. Ag nanoparticles were self-organized from a thin Ag film on a Si substrate through the RTA process. The mean diameter of the nanoparticles was modulated by changing the thickness of the Ag film. Furthermore, we controlled the surface energy of the Si substrate by changing the Ar or H2 ambient gas during the RTA process, and the modified surface energy was evaluated through water contact angle test. A smaller mean diameter of Ag nanoparticles was obtained under H2 gas at RTA, compared to that under Ar, from the same thickness of Ag thin film. This result was observed by SEM and summarized by statistical analysis. The mechanism of this result was determined by the surface energy change caused by the chemical reaction between the Si substrate and H2. The change of the surface energy affected on uniformity in the MCE process using Ag nanoparticles as catalyst. The nanoparticles formed under ambient Ar, having high surface energy, randomly moved in the lateral direction on the substrate even though the etching solution consisting of 10 % HF and 0.12 % H2O2 was cooled down to -20˚C to minimize thermal energy, which could act as the driving force of movement. On the other hand, the nanoparticles thermally treated under ambient H2 had low surface energy as the surface of the Si substrate reacted with H2. That's why the Ag nanoparticles could keep their pattern and vertically etch the Si substrate during MCE.

In this study, PtRu nanoparticles deposited on binary carbon supports were developed for use in direct methanol fuel cells using carbon blacks (CBs) and multi-walled carbon nanotubes (MWCNTs). The particle sizes and morphological structures of the catalysts were analyzed using X-ray diffraction and transmission electron microscopy, and the PtRu loading content was determined using an inductively coupled plasma-mass spectrometer. The electrocatalytic characteristics for methanol oxidation were evaluated by means of cyclic voltammetry with 1 M CH3OHin a 0.5 MH2SO4 solution as the electrolyte. The PtRu particle sizes and the loading level were found to be dependent on the mixing ratio of the two carbon materials. The electroactivity of the catalysts increased with an increasing MWCNT content, reaching a maximum at 30% MWCNTs, and subsequently decreased. This was attributed to the introduction of MWCNTs as a secondary support, which provided a highly accessible surface area and caused morphological changes in the carbon supports. Consequently, the PtRu nanoparticles deposited on the binary support exhibited better performance than those deposited on the single support, and the best performance was obtained when the mass ratio of CBs to MWCNTs was 70:30.

Silicon nanoparticle is a promising material for electronic devices, photovoltaics, and biological applications. Here, we synthesize silicon nanoparticles via CO2 laser pyrolysis and study the hydrogen flow effects on the characteristics of silicon nanoparticles using high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and UV-Vis-NIR spectrophotometry. In CO2 laser pyrolysis, used to synthesize the silicon nanoparticles, the wavelength of the CO2 laser matches the absorption cross section of silane. Silane absorbs the CO2 laser energy at a wavelength of 10.6μm. Therefore, the laser excites silane, dissociating it to Si radical. Finally, nucleation and growth of the Si radicals generates various silicon nanoparticle. In addition, researchers can introduce hydrogen gas into silane to control the characteristics of silicon nanoparticles. Changing the hydrogen flow rate affects the nanoparticle size and crystallinity of silicon nanoparticles. Specifically, a high hydrogen flow rate produces small silicon nanoparticles and induces low crystallinity. We attribute these characteristics to the low density of the Si precursor, high hydrogen passivation probability on the surface of the silicon nanoparticles, and low reaction temperature during the synthesis.

Nano-sized β-SiC nanoparticles were synthesized combined with a sol-gel process and a carbothermal process. TEOS and carbon black were used as starting materials for the silicon source and carbon source, respectively. SiO2 nanoparticles were synthesized using a sol-gel technique (Stober process) combined with hydrolysis and condensation. The size of the particles could be controlled by manipulating the relative rates of the hydrolysis and condensation reactions of tetraethyl orthosilicate (TEOS) within the micro-emulsion. The average particle size and morphology of synthesized silicon dioxide was about 100nm and spherical, respectively. The average particles size and morphology of the used carbon black powders was about 20nm and spherical, respectively. The molar ratio of silicon dioxide and carbon black was fixed to 1:3 in the preparation of each combination. SiO2 and carbon black powders were mixed in ethanol and ball-milled for 12 h. After mixing, the slurries were dried at 80˚C in an oven. The dried powder mixtures were placed in alumina crucibles and synthesized in a tube furnace at 1400~1500˚C for 4 h with a heating rate of 10˚C/min under flowing Ar gas (160 cc/min) and furnace cooling down to room temperature. SiC nanoparticles were characterized by XRD, TEM, and SAED. The XRD results showed that high purity beta silicon carbide with excellent crystallinity was synthesized. TEM revealed that the powders are spherical shape nanoparticles with diameters ranging from 15 to 30 nm with a narrow distribution.

목적: 본 연구는 furfuryl isocyanate를 은 나노 물질(Ag nanoparticler)과 기존의 하이드로젤 곤택트렌즈 재료와 공증합 하였으며, 제조된 콘택트렌즈의 물리적 특성을 비교하고, 내구성이 높은 콘택트렌즈 고분자로서의 활용성을 알아보았다. 방법: 교차결합제인 EGDMA(ethylene glycol dimethacrylate)와 HEMA(2-hydroxyethyl methacry-Late), MMA(methyl methacrylate), MA(merhacrylic acid) 그리고 개시제인 AIBN(azobisisobutyronitrile)과 함께 공증합 하였다. 결과: 생성된 고분자의 물리적 특성을 측정한 결과, 함수율 28.98~34.31%, 굴절률 1.441~1.453,UV-B투고율 33.2~72.0%, 접촉각 57.65~79.00° 그리고 인장강도의 경우 0.340~0.71kgf 범위의 분포를 나타내었다. 또한 은 나노 물질 1%에 furfuryl isocyanate를 첨가할수록 UV-B 투과율 저하와 인장강도가 증가한 결과를 보였다. 결론: 본 실험결과로 볼 때 생성된 공중합체는 내구성이 좋고 자외선 차단 효과가 있는 렌즈 재료로 유용하게 활용될 것으로 기대된다.

We describe the preparation of superparamagnetic nanoclusters (SNCs) by fine-tuning of the seed Fe3O4 nanoparticle sizes to enhance and their T2 relaxivity can be increased by > 4-fold. Therefore, with 11 nm seed core and PVA coating, SNC-11 exhibit a higher T2 relaxivity than other cluster condition. So fabricating the cluster, seed size is the most important influence the T2 relaxivity. As well as, in vitro cellular imaging results demonstrated the strong potential of SNCs for clinical applications by targeting affinity. According to the experiments, with 11 nm seed core and PVA coating, SNC-11 exhibited the highest T2 relaxivity of 454 mM-1s-1 due to the strong seed size effect on their magnetic sensitivity, indicating superior magnetic resonance (MR) contrast efficiency. Further in vitro cellular imaging results demonstrated the strong potential of SNCs for clinical applications.