• Bulletin of the Korean Chemical Society
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• v.27 no.11
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• pp.1809-1814
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• 2006

The L-Valinate anion coordinating zinc complex, [$Zn(val)_2(H-2O)$], was isolated and structurally characterized by single crystal X-ray crystallography. The crystal possess orthorhombic symmetry with a space group $P2_12_12_1$, Z = 4, and a = 7.4279(2)$\AA$, b = 9.4342(2)$\AA$, c =20.5862(7)$\AA$ respectively. The compound features a penta-coordinate zinc ion in which the two valine anion molecules are directly coordinating the central zinc metal ion via their N (amine) and O (carboxylate) atoms, and an additional coordination to zinc is made by water molecule (solvent) to form a distorted square pyramidal structure. In addition, further synthesis of the valine capped ZnS:Mn nanocrystal from the reaction of [$Zn(val)_2(H-2O)$] precursor with $Na_2S$ and 1.95 weight % of $Mn^{2+}$ dopant is described. Obtained valine capped nanocrystal was water dispersible and was optically characterized by UV-vis and solution PL spectroscopy. The solution PL spectrum for the valine capped ZnS:Mn nanocrystal showed an excitation peak at 280 nm and a very narrow emission peak at 558 nm respectively. The measured and calculated PL efficiency of the nanocrystal in water was 15.8%. The obtained powders were characterized by XRD, HR-TEM, and EDXS analyses. The particle size of the nanocrystal was also measured via a TEM image. The measured average particle size was 3.3 nm.

• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1181-1187
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• 2013

Water-dispersible ZnS:Mn nanocrystals were synthesized by capping the surface of the nanocrystal with O-(2-Aminoethyl)polyethylene glycol (PEG-$NH_2$, Mw = 10,000 g/mol) and O-(2-Carboxyethyl)polyethylene glycol (PEG-COOH, Mw = 10,000 g/mol) molecules. The modified PEG capped ZnS:Mn nanocrystal powders were thoroughly characterized by XRD, HR-TEM, EDXS, ICP-AES and FT-IR spectroscopy. The optical properties were also measured by UV/Vis and photoluminescence (PL) spectroscopies. The PL spectra showed broad emission peaks at 600 nm with similar PL efficiencies of 7.68% (ZnS:Mn-PEG-NH2) and 9.18% (ZnS:Mn-PEG-COOH) respectively. The measured average particle sizes for the modified PEG capped ZnS:Mn nanocrystals by HR-TEM images were 5.6 nm (ZnS:Mn-PEG-NH2) and 6.4 nm (ZnS:Mn-PEG-COOH), which were also supported by Debye-Scherrer calculations. In addition, biological toxicity effects of the nanocrystals over the growth of wild type E. coli were investigated. They showed no biological toxicity to E. coli until very high concentration dosage of 1 mg/mL of the both nanocrystal samples.

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1741-1747
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• 2012

Water-dispersible ZnS:Mn nanocrystals were synthesized by capping the surface of the nanocrystals with conventional aminoacids ligands: serine and threonine. The aminoacids capped ZnS:Mn nanocrystal powders were characterized by XRD, HR-TEM, EDXS, ICP-AES and FT-IR spectroscopy. The optical properties were also measured by UV/Vis and solution photoluminescence (PL) spectroscopies in aqueous solvents. The solution PL spectra showed broad emission peaks around 600 nm with PL efficiencies of 9.7% (ZnS:Mn-Ser) and 15.4% (ZnS:Mn-Thr) respectively. The measured particle sizes for the aminoacid capped ZnS:Mn nanocrystals by HR-TEM images were about 3.0-4.0 nm, which were also supported by Debye-Scherrer calculations. In addition, cytotoxic effects of four aminoacids capped ZnS:Mn nanocrsystals over the growth of wild type E. coli were investigated. Although toxicity in the form of growth inhibition was observed with all the aminoacids capped ZnS:Mn nanocrystals at higher dose (1 mg/mL), ZnS:Mn-Met and ZnS:Mn-Thr appeared non-toxic at doses less than 100 ${\mu}g$/mL. Low biological toxicities were seen at doses less than 10 ${\mu}g$/ mL for all nanocrystals.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3834-3837
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• 2010

• Journal of the Korean Chemical Society
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• v.53 no.5
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• pp.505-511
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• 2009

Water soluble ZnS nanocrystals were synthesized by capping the surface of the nanocrystals with valine and alanine molecules, which are structurally simple and bio friendly amino acids. The obtained ZnS nanocrystal powders were characterized by XRD, HR-TEM, and EDXS spectroscopies. The measured particle sizes by HR-TEM images were in the range of 3.3 to 3.6 nm. In addition, the surface capping amino acids molecules were characterized by FT-IR and FT-Raman spectroscopies.

• Bulletin of the Korean Chemical Society
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• v.28 no.7
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• pp.1091-1096
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• 2007

Water dispersible ZnS:Mn nanocrystals were synthesized by capping the surface of the nanocrystals with four kinds of aminoacids ligands: arginine, cystein, histidine, and methionine. The aminoacids capped ZnS:Mn nanocrystal powders were characterized by XRD, HR-TEM, EDXS, and FT-IR spectroscopy. The optical properties of the aminoacids capped ZnS:Mn colloidal nanocrystals were also measured by UV/Vis and solution photoluminescence (PL) spectroscopies in aqueous solvents. The solution PL spectra showed broad emission peaks around 575 nm (orange light emissions) with PL efficiencies in the range of 4.4 to 7.1%. The measured particle sizes for the aminoacid capped ZnS:Mn nanocrystals by HR-TEM images were in the range of 5.3 to 11.7 nm.

• Korean Journal of Materials Research
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• v.18 no.7
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• pp.379-383
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• 2008

We report on the light-emitting diode (LED) characteristics of core-shell CdSe/ZnS nanocrystal quantum dots (QDs) embedded in $TiO_2$thin films on a Si substrate. A simple p-n junction could be formed when nanocrystal QDs on a p-type Si substrate were embedded in ${\sim}5\;nm$ thick $TiO_2$ thin film, which is inherently an n-type semiconductor. The $TiO_2$ thin film was deposited over QDs at $200^{\circ}C$ using plasma-enhanced metallorganic chemical vapor deposition. The LED structure of $TiO_2$/QDs/Si showed typical p-n diode currentvoltage and electroluminescence characteristics. The colloidal core-shell CdSe/ZnS QDs were synthesized via pyrolysis in the range of $220-280^{\circ}C$. Pyrolysis conditions were optimized through systematic studies as functions of synthesis temperature, reaction time, and surfactant amount.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.657-662
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• 2012

Mercaptoacetic acid (MAA) and mercaptopropionic acid (MPA) capped ZnS:Mn nanocrystals were synthesized and their physical characteristics were examined by XRD, HR-TEM, EDXS, and FT-IR spectroscopy. The optical properties of the MPA capped ZnS:Mn nanocrystals dispersed in aqueous solution were also measured by UV/Vis and solution photoluminescence (PL) spectra, which showed a broad emission peak around 598 nm (orange light emissions) with calculated relative PL efficiency of 5.2%. Comparative toxicity evaluation of the uncoordinated ligands, MAA and MPA, with the corresponding ZnS:Mn nanocrystals revealed that the original ligands significantly suppressed the growth of wild type E. coli whereas the ligandcapped nanocrystals did not show significant toxic effects. The reduced cytotoxicity of the conjugated ZnS:Mn nanocrystals was also observed in NIH/3T3 mouse embryonic fibroblasts. These results imply that potential toxicities of the capping ligands can be neutralized on ZnS:Mn surface.

• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.1169-1176
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• 2014

In this study, water-dispersible ZnS:Mn nanocrystals were synthesized by capping the surface with conventional and simple structured amino acid ligands: $\small{L}$-Glycine and $\small{L}$-Alanine. The ZnS:Mn-Gly and ZnS:Mn-Ala nanocrystal powders were characterized by XRD, HR-TEM, EDXS, ICP-AES, and FT-IR spectroscopy. The optical properties were measured by UV-Visible and photoluminescence (PL) spectroscopy. The PL spectra for the ZnS:Mn-Gly and ZnS:Mn-Ala showed broad emission peaks at 599 nm and 607 nm with PL efficiencies of 6.5% and 7.8%, respectively. The measured average particle size from the HR-TEM images were $6.4{\pm}0.8$ nm (ZnS:Mn-Gly) and $4.1{\pm}0.5$ nm (ZnS:Mn-Ala), which were also supported by Debye-Scherrer calculations. In addition, the degree of aggregation of the nanocrystals in aqueous solutions were measured by a hydrodynamic light scattering method, which showed formation of sub-micrometer size aggregates for both ZnS:Mn-Gly ($273{\pm}94$ nm) and ZnS:Mn-Ala ($233{\pm}34$ nm) in water due to the intermolecular attraction between the capping amino acids molecules. Finally, the cytotoxic effects of ZnS:Mn-Gly and ZnS:Mn-Ala nanocrsystals over the growth of wild type E. coli were investigated. As a result, no toxicity was shown for the ZnS:Mn-Gly nanocrystal in the colloidal concentration region from 1 ${\mu}g/mL$ to 1000 ${\mu}g/mL$, while ZnS:Mn-Ala showed significant toxicity at 100 ${\mu}g/mL$.

• Bulletin of the Korean Chemical Society
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• v.29 no.6
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• pp.1247-1249
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• 2008