• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.4
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• pp.255-262
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• 2016

Effects of $SiO_x$ or C shells on electrochemical properties of Si nanoparticles were investigated. $SiO_x$ shells with thickness of 10~15 nm were formed on homogeneously crystalline Si nanoparticles. Incase of Si-C nanoparticles, there were 30~40 layers of C with a number of defects. Li-ion batteries were fabricated with the above-mentioned nanoparticles, and their electrochemical properties were measured. Pristine Si shows a high IRC (initial reversible capacity) of 2,517 mAh/g and ICE (initial columbic efficiency) of 87%, but low capacity retention of 22%, respectively. $SiO_x$ shells decreased IRC (1,534 mAh/g) and ICE (54%), while the retention increased up to 65%, which can be explained by irreversible phases such as $LiO_2$ and $Li_2SiO_3$. C shells exhibited no differences in IRC and ICE compared to the pristine Si but an enhanced retention of 54%, which might be from proper defect structures.

• Bulletin of the Korean Chemical Society
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• v.34 no.2
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• pp.539-544
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• 2013

$Ag@SiO_2@SiO_2$(FITC) nanocomposites were prepared by the simple polyol process and St$\ddot{o}$ber method. Fluorescence enhancement of fluorescein moiety (fluorescein isothiocyanate, FITC) was investigated in the presence of silver nanoparticles in $Ag@SiO_2@SiO_2$(FITC) system with varying thickness (X nm) of first silica shell. Maximum enhancement factor of 4.3 fold was achieved in $Ag@SiO_2@SiO_2$(FITC) structure with the first silica shell thickness of 8 nm and the average separation distance of 11 nm between the surface of silver nanoparticle and fluorescein moiety. The enhancement is believed to be originated from increased excitation rate of fluorescein moiety due to concentrated local electromagnetic field which was improved by interaction of light with silver nanoparticles.

• Analytical Science and Technology
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• v.20 no.5
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• pp.413-418
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• 2007

Poly(vinylpyrrolidone) stabilized cadmium sulfide (CdS) nanoparticles were loaded onto the surface of silica ($SiO_2$) nanoparticles by using ${\gamma}$-irradiation. TEM micrograph reveals the presence of ~20nm sized CdS nanoparticles on the surface of $SiO_2$ nanoparticles. XRD patterns confirm the crystalline. PL spectra of the simple PVP-stabilized CdS nanoparticle and $SiO_2$@CdS composite confirm the differences in the emission characteristics between them. Two prominent emission peaks were noted around 550 nm and 600 nm for PVP-stabilized CdS nanoparticles). The emission peaks noted for the PVP-stabilized CdS nanoparticles were found to be blue shifted for $SiO_2$@CdS composites. Besides, an additional emission peak around 450 nm was noticed for the $SiO_2$@CdS composite. The presence of CdS nanoparticles influence the emission characteristics and induce quantum confinement effect.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.197-198
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• 2009

This paper describes the Raman scattering characteristics of polycrystalline (poly) 3C-SiC films, which were deposited on the thermally oxidized Si(100) substrate by the atmosphere pressure chemical vapor deposition (APCVD) method according to growth temperature. TO and LO phonon modes to 2.0m thick poly 3C-SiC deposited at $1180^{\circ}C$ were measured at 794.4 and $965.7\;cm^{-1}$ respectively. From the intensity ratio of $I_{(LO)}/I_{(TO)}$ 1.0 and the broad full width half maximum (FWHM) of TO modes, itcan be elucidated that the crystallinity of 3C-SiC forms polycrystal instead of disordered crystal and the crystal defect is small. At the interface between 3C-SiC and $SiO_2$, $1122.6\;cm^{-1}$ related to C-O bonding was measured. Here poly 3C-SiC admixes with nanoparticle graphite with the Raman shifts of D and G bands of C-C bonding 1355.8 and $1596.8\;cm^{-1}$. Using TO mode of 2.0 m thick poly 3C-SiC, the biaxial stress was calculated as 428 MPa.

• Journal of Environmental Science International
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• v.22 no.1
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• pp.73-81
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• 2013

The present work has been devoted to the catalytic reduction of $N_2O$ by $H_2$ with $Pt/SiO_2$ catalysts at very low temperatures, such as $110^{\circ}C$, and their nanoparticle sizes have been determined by using $H_2-N_2O$ titration, X-ray diffraction(XRD) and high-resolution transmission electron microscopy(HRTEM) measurements. A sample of 1.72% $Pt/SiO_2$, which had been prepared by an ion exchange method, consisted of almost atomic levels of Pt nanoparticles with 1.16 nm that are very consistent with the HRTEM measurements, while a $Pt/SiO_2$ catalyst possessing the same Pt amount via an incipient wetness technique did 13.5 nm particles as determined by the XRD measurements. These two catalysts showed a noticeable difference in the on-stream $deN_2O$ activity maintenance profiles at $110^{\circ}C$. This discrepancy was associated with the nanoparticle sizes, i.e., the $Pt/SiO_2$ catalyst with the smaller particle size was much more active for the $N_2O$ reduction. When repeated measurements of the $N_2O$ reduction with the 1.16 nm Pt catalyst at $110^{\circ}C$ were allowed, the catalyst deactivation occurred, depending somewhat on regeneration excursions.

• Biomolecules & Therapeutics
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• v.19 no.2
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• pp.261-266
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• 2011

As recent reports suggest that nanoparticles may penetrate into cell membrane and effect DNA condition, it is necessary to assay possible cytotoxic and genotoxic risk. Three different sizes of magnetic nanoparticle silica (MNP@$SiO_2$) (50, 100 and 200 nm diameter) were tested for cytotoxicity and DNA damage using L5178Y cell. MNP@$SiO_2$ had constant physicochemical characteristics confirmed by transmission electron microscope, electron spin resonance spectrometer and inductively coupled plasma-atomic emission spectrometer for 48 h. Treatment of MNP@$SiO_2$ induced dose and time dependent cytotoxicity. At 6 h, 50, 100 or 200 nm MNP@$SiO_2$ decreased significantly cell viability over the concentration of 125 ${\mu}g/ml$ compared to vehicle control (p<0.05 or p<0.01). Moreover, at 24 h, 50 or 100 nm MNP@$SiO_2$ decreased significantly cell viability over the concentration of 125 ${\mu}g/ml$(p<0.01). And treatment of 200 nm MNP@$SiO_2$ decreased significantly cell viability at the concentration of 62.5 ${\mu}g/ml$ (p<0.05) and of 125, 250, 500 ${\mu}g/ml$ (p<0.01, respectively). Furthermore, at 48 h, 50, 100 or 200 nm MNP@$SiO_2$ decreased significantly cell viability at the concentration of 62.5 ${\mu}g/ml$ (p<0.05) and of 125, 250, 500 ${\mu}g/ml$ (p<0.01, respectively). Cellular location detected by confocal microscope represented they were existed in cytoplasm, mainly around cell membrane at 2 h after treatment of MNP@$SiO_2$. Treatment of 50 nm MNP@$SiO_2$ significantly increased DNA damage at middle and high dose (p<0.01), and treatment of 100 nm or 200 nm significantly increased DNA damage in all dose compared to control (p<0.01). Taken together, treatment of MNP@$SiO_2$ induced cytotoxicity and enhanced DNA damage in L5178Y cell.

• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.1067-1072
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• 2014

In this study, we report a new approach for $Mn_3O_4$-graphene nanocomposite by ex situ method. This nanocomposite shows two-dimensional aggregation of nanoparticle, and doping effect by decorated manganese oxide ($Mn_3O_4$), as well. The graphene film was made through micromechanical cleavage of graphite on the $SiO_2/Si$ wafer. Manganese oxide ($Mn_3O_4$) nanoparticle with uniform cubic shape and size (about $5.47{\pm}0.61$ nm sized) was synthesized through the thermal decomposition of manganese(II) acetate, in the presence of oleic acid and oleylamine. The nanocomposite was obtained by self-assembly of nanoparticles on graphene film, using hydrophobic interaction. After heat treatment, the decorated nanoparticles have island structure, with one-layer thickness by two-dimensional aggregations of particles, to minimize the surface potential of each particle. The doping effect of $Mn_3O_4$ nanoparticle was investigated with Raman spectra. Given the upshift in positions of G and 2D in raman peaks, we suggest that $Mn_3O_4$ nanoparticles induce p-doping of graphene film.

• Journal of the Korean Society of Clothing and Textiles
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• v.37 no.2
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• pp.224-234
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• 2013

This study investigates the fabrication of core-sheath nanocomposite fibers by locating germanium (Ge) and silicon dioxide ($SiO_2$) nanoparticles selectively in the sheath layer by co-axial electrospinning. Co-axially spun fibers were prepared by electrospinning a pure PVA solution and Ge/$SiO_2$/PVA solution as the core and sheath layer, respectively. Core-sheath nanocomposite fibers were electrospun under a variety of conditions that include various feed rates for the core and sheath solutions, voltages, and concentric needle diameters, in order to find an optimum spinning condition. Ge/$SiO_2$ nanocomposite fibers were also prepared by uniaxial electrospinning to compare fiber morphology and nanoparticle distribution with core-sheath nanofibers. Using scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray analysis, it was demonstrated that the co-axial approach resulted in the presence of nanoparticles near the surface region of the fibers compared to the overall distribution obtained for uni-axial fibers. The co-axially electrospun Ge/$SiO_2$/PVA nanofiber webs have possible uses in high efficiency functional textiles in which the nanoparticles located in the sheath region provide enhanced functionality.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.84.2-84
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• 2003

• Proceedings of the Korea Association of Crystal Growth Conference
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• 2000.06a
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• pp.35-58
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• 2000

The demand for sub-micrometer or nanometer functional ceramic powders with a better suspension behavior in aqueous media in increasing. Redispersible barium titanate (BT) nanocrystals, green light emitting Mn2+ doped Zn$_2$SiO$_4$ and ZnS nanoparticle phosphors were synthesized by a hydrothermal method or chemical precipitation with surface modification. The nanoparticle redispersibility for BT was achieved by using a polymeric surfactant. X-ray diffraction(XRD) results indicated that the BT particles are of cubic phase with 80 nm in size. XRD results of zinc silicate phosphor indicate that seeds play an important role in enhancing the nucleation and crystallization of Zn$_2$SiO$_4$ crystals in a hydrothermal condition. This paper describes and discuss the methods of surface modification, and the resulting related properties for BT, zinc silicate and zinc sulfide.