• 한국재료학회지
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• 제30권7호
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• pp.338-342
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• 2020

Tin oxide (SnO₂) nanocrystals are synthesized by a thermal evaporation method using a mixture of SnO₂ and Mg powders. The synthesis process is performed in air at atmospheric pressure, which makes the process very simple. Nanocrystals with a belt shape start to form at 900 ℃ lower than the melting point of SnO₂. As the synthesis temperature increases to 1,100 ℃, the quantity of nanocrystals increases. The size of the nanocrystals did not change with increasing temperature. When SnO₂ powder without Mg powder is used as the source material, no nanocrystals are synthesized even at 1,100 ℃, indicating that Mg plays an important role in the formation of the SnO₂ nanocrystals at temperatures as low as 900 ℃. X-ray diffraction analysis shows that the SnO₂ nanocrystals have a rutile crystal structure. The belt-shaped SnO₂ nanocrystals have a width of 300~800 nm, a thickness of 50 nm, and a length of several tens of micrometers. A strong blue emission peak centered at 410 nm is observed in the cathodoluminescence spectra of the belt-shaped SnO₂ nanocrystals.

• Bulletin of the Korean Chemical Society
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• 제27권7호
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• pp.961-971
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• 2006

Shape controlled synthesis of inorganic nanocrystals is one of the important issues in materials chemistry due to their novel shape dependent properties. Although various shapes of nanocrystals have been developed, a systematic account on the shape control of these nanocrystals still remains an important subject in materials chemistry. In this article, we will overview the recent developments in the geometrical shape evolution of semiconductor and metal oxide nanocrystals obtained by nonhydrolytic synthetic methods. Many structurally unprecedented motifs have appeared as zero-dimesional (D) polyhedrons, one-D rods and wires, two-D plates and prisms, and other advanced shapes such as branched rods, stars, and inorganic dendrites. Important parameters which determine the geometrical shapes of nanocrystals are also illustrated. In addition, as a possible application of such nanocrystals for biomedical sciences, we further describe their utilizations for cancer diagnosis through nanocrystal-assisted magnetic resonance imaging (MRI).

• 펄프종이기술
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• 제43권4호
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• pp.67-75
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• 2011

Sulfuric acid hydrolysis is a typical approach for producing cellulose nanocrystals. The method has been widely used, but it has a disadvantage of low yield of cellulose nanocrystals compared to mechanical method. To expand the application of cellulose nanocrystals in practical, we should be able to produce them with higher yield and the controlled properties. In this study, therefore, we intended to investigate the effect of sulfuric acid hydrolysis condition on the characteristics of the prepared cellulose nanocrystals. The concentration of sulfuric acid, temperature and hydrolysis time were varied, and the yield as well as diverse properties including the morphology, size and zeta potential were examined. We could obtain cellulose nanocrystals up to 70% of yield and found that the properties were dependent on the reaction condition. It would be helpful to select an appropriate condition for producing cellulose nanocrystals.

• Journal of the Optical Society of Korea
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• 제15권4호
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• pp.407-414
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• 2011

We analyze the cooperative spontaneous emission of optically excited nanocrystals into surface plasmon polaritons propagating on the surface of a cylindrical metallic nanowire. The spontaneous emission probability of the nanocrystals is obtained by perturbative expansions with and without dipole-dipole interaction among nanocrystals in order to see the cooperative effects. The spontaneous emission probability depends on the radial and axial distributions, as well as on the dipolar orientation of nanocrystals. It is shown that the spontaneous emission probability is strongly influenced by dipole-dipole interaction, axial distribution, and dipolar orientation of nanocrystals for closely spaced nanocrystals.

• 통합자연과학논문집
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• 제2권3호
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• pp.219-223
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• 2009

Easy and simple synthesis of CdSe nanocrystals was achieved through sol-gel process. CdSe nanocrystals were synthesized from the reaction of cadmium oxide and selenium in the prescence of trioctylphosphine oxide, tributylphosphine, octadecene, octadecylamine, and stearic acid. The effect of reaction temperature for the determination of size of CdSe nanocrystals was investigated after the addition of selenium. The reaction temperature for the growth of CdSe nanocrystals was increased by every $20^{\circ}C$ from 170 to 190, 210, 230, 250, 270, and $290^{\circ}C$. When the reaction temperature was higher, the absorption wavelength in the absorption spectrum was increased which indicated that the size of CdSe nanocrystals was increased. The emission wavelength in the photoluminescence spectrum was increased from 438 to 489, 542, 591, 643, 692, and 745 nm, as the size of CdSe nanocrystals was increased. The control of the reaction temperature illustrated that the color tuning of emission wavelength were successfully obtained.

• 한국분말재료학회지
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• 제22권6호
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• pp.385-390
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• 2015

We report a synthesis of non-toxic InP nanocrystals using non-pyrolytic precursors instead of pyrolytic and unstable tris(trimethylsilyl)phosphine, a popular precursor for synthesis of InP nanocrystals. In this study, InP nanocrystals are successfully synthesized using hexaethyl phosphorous triamide (HPT) and the synthesized InP nanocrystals showed a broad and weak photoluminescence (PL) spectrum. As synthesized InP nanocrystals are subjected to further surface modification process to enhance their stability and photoluminescence. Surface modification of InP nanocrystals is done at $230^{\circ}C$ using 1-dodecanethiol, zinc acetate and fatty acid as sources of ZnS shell. After surface modification, the synthesized InP/ZnS nanocrystals show intense PL spectra centered at the emission wavelength 612 nm through 633 nm. The synthesized InP/ZnS core/shell structure is confirmed with X-ray diffraction (XRD) and Inductively Coupled Plasma - Atomic Emission Spectrometer (ICP-AES). After surface modification, InP/ZnS nanocrystals having narrow particle size distribution are observed by Field Emission Transmission Electron Microscope (FE-TEM). In contrast to uncapped InP nanocrystals, InP/ZnS nanocrystals treated with a newly developed surface modified procedure show highly enhanced PL spectra with quantum yield of 47%.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.21.1-21.1
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• 2011

Controlling the morphology of a metal nanocrystal is critical to modern materials chemistry because its physical and chemical properties can be easily and widely tuned by tailoring the size and shape. Combined with ease of synthesis and processing, metal nanocrystals with desired morphologies and thus properties are promising candidates for a wide variety of applications in catalysis, sensing, imaging, electronics, and photonics, and medicine. In this talk, I would like to introduce my recent research results on the shape-controlled synthesis of metal nanocrystals using a simple aqueous method. This water-based system provides a number of merits such as simplicity, convenience, and the potential for large-scale production and enables us to synthesize metal nanocrystals with a rich variety of shapes such as truncated octahedron, cubes, bars, octahedrons, and thin plates. The ability to control the shape of metal nanocrystals provides a great opportunity to systematically investigate their catalytic and optical properties.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.101-101
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• 2007

We fabricated floating gate non-volatile memory devices with Si nanocrystals embedded in $SiN_x$ layer to achieve higher trap density. The average size of Si nanocrystals embedded in $SiN_x$ layer was ranging from 3 nm to 5 nm. The MOS capacitor and MOSFET devices with Si nanocrystals embedded in $SiN_x$ layer were analyzed the charging effects as a function of Si nanocrystals size.

• Bulletin of the Korean Chemical Society
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• 제33권2호
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• pp.393-397
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• 2012

We report a new route to synthesize high quality zinc blende CdS and ZnS nanocrystals in noncoordinating solvent 1-octadecene, using dodecanethiol (DDT) molecules as both the sulfur source and surface capping ligands. Different reaction temperatures and Cd(Zn)/DDT molar ratios were tested to optimize the synthesis conditions. Absorption photoluminescence (PL) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) pattern, and transmission electron microscopy (TEM) were used to characterize assynthesized nanocrystals. The narrow half width at the half-maximum on the long wavelength side of the firstexcitonic absorption peak and TEM images demonstrated nearly monodisperse size distributions of asprepared CdS, ZnS, and CdS/ZnS core/shell nanocrystals. Only trap emissions of the nanocrystals were detected when the amount of DDT was excessive, this came from the strong quenching effect of thiol groups on the nanocrystal surfaces. After overcoating with ZnS shells, band-gap emissions of CdS nanocrystals were partially recovered.

• Korean Chemical Engineering Research
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• 제51권3호
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• pp.403-406
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• 2013

이 논문에서는 6-aminohexanoic acid (AHA)를 사용해서 물에 분산이 잘되는 균일한 maghemite 나노입자를 제조하는 방법을 설명한다. 물에 분산되는 maghemite 나노입자는 $195^{\circ}C$의 octyl ether와 AHA의 혼합물에 $Fe(CO)_5$를 넣어주는 방법으로 제조하였다. 제조된 나노입자는 좋은 결정성과 자성을 띄고 있으며 물에서 상당한 안정성을 보여주었다. 또한 ligand-exchange 방식으로 물에 분산되는 maghemite 나노입자를 제조하는 방법도 가능함을 확인하였다. 본 연구에서는 AHA를 이용하여 물에 분산된 금속 산화물 나노입자를 제조하는 새로운 대안을 제시하였다.