• Mycobiology
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• v.35 no.3
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• pp.150-153
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• 2007

New $N_2O_2$ donor type Schiff base has been designed and synthesized by condensing acetoacetanilido-4-aminoantipyrine with 2-aminobenzoic acid in ethanol. Solid metal complexes of the Schiff base with Cu(II), Ni(II), Co(II), Mn(II), Zn(II), VO(IV), Hg(II) and Cd(II) metal ions were synthesized and characterized by elemental analyses, magnetic susceptibility, molar conduction, fast atom bombardment (FAB) mass, IR, UV-Vis, and $^1H$ NMR spectral studies. The data show that the complexes have the composition of ML type. The UV-Vis. and magnetic susceptibility data of the complexes suggest a square-planar geometry around the central metal ion except VO(IV) complex which has square-pyramidal geometry. The in vitro antifungal activities of the compounds were tested against fungi such as Aspergillus niger, Aspergillus flavus, Rhizopus stolonifer, Candida albicans, Rhizoctonia bataicola and Trichoderma harizanum. All the metal complexes showed stronger antifungal activities than the free ligand. The minimum inhibitory concentrations (MIC) of the metal complexes were found in the range of $10{\sim}31{\mu}g/ml$.

• Bulletin of the Korean Chemical Society
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• v.34 no.7
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• pp.1959-1960
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• 2013

• Applied Chemistry for Engineering
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• v.21 no.4
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• pp.445-451
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• 2010

$TiO_2$ shows considerably efficient photoreaction activity under the ultraviolet range but it has disadvantage that there is no activity in the visible light range. In this study, it was tried to find a solution for the problem of this kind of photocatalyst by utilizing transition metal, which can show electronic transition with $TiO_2$ in the visible light area. Photocatalyst was prepared, which can have photocatalytic activity in the wide wavelength range, not only ultraviolet region but also visible light area and prevent the combination of electron and hole hindering the photoreaction. For this purpose, by using the ion exchange method, $TiO_2$ precursor and transition metal precursor were dipped into H typed strong acid ion-exchange resin. And two kind photocatalysts (Ti-M-SCM) in which transition metal and titanium dioxide coexist through the carbonization/activation process was prepared. Moreover, photolytic reaction under the wavelength 254 nm and 365 nm was performed for humic acid (HA) in the continuous reactor in order to estimate the efficiency of produced Ti-M-SCM.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.385-385
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• 2012

Understanding the thermodynamics and structural transformation during the Metal-Insulator Transition (MIT) is critical to better understand the underlying physical origin of phase transition in the vanadiumdioxide ($VO_2$). Here, through the temperature-dependent in-situ high resolutiontransmission electron microscopy (HR-TEM), and systematic electrical transport study, we have shown that the tunable MIT transition of $VO_2$ nanowires is strongly affected by interplay between strain and domain nucleation by ion beam irradiation. Surprsingly, we have also observed that the $VO_2$ rutile (R) metallic phase could form directly in a strain-induced metastable monoclinic (M2) phase. These insights open the door toward more systematic approaches to synthesis for $VO_2$ nanostructures in desired phase and to use for applications including ultrafast optical switching, smart window, metamaterial, resistance RAM and synapse devices.

• Bulletin of the Korean Chemical Society
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• v.24 no.5
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• pp.573-578
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• 2003

The structural, magnetic, and transport properties of a mono-layered manganite $La_{0.7}Sr_{1.3}MnO_{4+{\delta}}$ were investigated using variable temperature neutron powder diffraction as well as magnetization and transport measurements. The compound adopts the tetragonal I4/mmm symmetry and exhibits no magnetic reflection in the temperature region of 10 K ≤ T ≤ 300 K. A weak ferromagnetic (FM) transition occurs about 130 K, which almost coincides with the onset of a metal-insulator (M-I) transition. Extra oxygen that occupies the interstitial site between the [(La,Sr)O] layers makes the spacing between the [MnO₂] layers shorten, which enhances the inter-layer coupling and eventually leads to the M-I transition. We also found negative magneto resistance (MR) below the M-I transition temperature, which can be understood on the basis of the percolative transport via FM metallic domains in the antiferromagnetic (AFM) insulating matrix.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.143.2-143.2
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• 2013

Nanomechanical and electrical properties of vanadium dioxide (VO2) thin films across thermal-driven phase transition are investigated with ultra-high vacuum atomic force microscopy. VO2 thin films have been deposited on the n-type heavily doped silicon wafer by pulsed laser deposition. X-ray diffraction reveals that it is textured polycrystalline with preferential orientation of (100) and (120) planes in monoclinic phase. As the temperature increases, the friction decreased at the temperature below the transition temperature, and then the friction increased as increasing temperature above the transition temperature. We attribute this observation to the combined effect of the thermal lubricity and electronic contribution in friction. Furthermore, the dependence of nanoscale conductance on the local pressure was indicated at the various temperatures, and the result was discussed in the view of pressure-induced metal-insulator transition.

• Journal of the Korean Chemical Society
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• v.36 no.6
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• pp.802-811
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• 1992

The conformations of several carbene-olefin-transition metal complexes[$(CO)_4M$-(CHX)olefin] (X: $OCH_3,\;NHCH_3,\;SCH_3$, M: C, Mo, W) have been studied by means of Extend Huckel calculations. In the case of $d^6$ transition metal octahedral complexes, it is shown that the two main factors which determine the optimal conformation are metal-to-ligand back-donation and direct ligand-ligand interaction at the metal, but the ligand-ligand interaction dominates the situation for a metal that is coordinated to $\pi$ acceptor ligands and to $\pi$ donor group on the carbene. The relative amounts of both factors depend strongly on the electronic nature of the ligands at the metal. The greater electron donating ability of nitrogen stabilizes amino-substituted carbene complexes compared with their alkoxyl substituted analogues. This interaction is optimal when the $\pi$ systems of the carbene and olefin are coplanar. The introduction of the $\pi$ donor group on the carbene carbon increases also the importance of the ligand-ligand interaction.

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.181-188
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• 2013

The effect of transition metal ion exchange into UZM-9 zeolite with LTA framework on its deactivation in methanol-to-olefin (MTO) conversion was discussed. The ion exchange of copper, cobalt, nickel, and iron did not induce any notable change in the crystallinity, crystal morphology, and acidity of UZM-9. The small cage entrance of UZM-9 caused the high selectivity to lower olefins in the MTO conversion, while its large cages allowed the rapid further cyclecondensation of active intermediates, polymethylbenzenes including hexamethylbenzene, resulting in a rapid deactivation. The UZM-9 containing copper and cobalt ions showed considerably slow deactivations. The interaction between transition metal ions and polymethylbenzene cation radicals, the active intermediates, generated in the MTO conversion stabilized the radicals and slowed down the deactivation of UZM-9.

• Textile Coloration and Finishing
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• v.17 no.2 s.81
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• pp.10-18
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• 2005

Silk fabrics mordanted with $Fe^{2+},\;Ni^{2+},\;and\;Cu^{2+}$ were dyed with the aqueous extract of Cassia tora L. seed which was known to include water soluble colorant kaempferol, one of flavonol compounds. Kaempferol can react with free radicals and chelate transition metal ions, which is thought to catalyze processes leading to the appearance of free radicals and have antioxidant activity. In relation to the coordinating and chelating mechanism of the ions with the silk protein and kaempferol, reasonable conclusions should be made on the colorant uptake and the water fastness of the fabric. The amount of the colorant on the fabric was in the order of $Fe^{2+}>Ni^{2+}>Cu^{2+}$. In case of dyeing through coordinaiton bonds between transition metal ions and silk protein and colorants, it was thought that the ions with the smaller secondary hydration shell, the higher preference to the atoms of the ligand coordinated, and the suitable bonding stability for the substitution of primarily hydrated water molecules for colorants led to the higher colorant uptake. The water fastnsess of the fabric was in the order of $Fe^{2+}>Cu^{2+}>Ni^{2+}$. It should be reasonable to choose transition metal ions with weak and strong tendency to the ionic and the coordination bond, respectively, to the carboxylate anion of the silk protein. Although further research needs to be done, the conclusions above may be generally applied to the natural dyeing through the coordination bond mechanism between transition metal ions and colorants and substrates.

• Bulletin of the Korean Chemical Society
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• v.25 no.5
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• pp.694-698
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• 2004

A new method for the simultaneous determination of seven transition metal ions in water and food by microcolumn high-performance liquid chromatography has been developed. The lead, cadmium, mercury, nickel, cobalt, silver and tin ions were pre-column derivatized with tetra-(4-aminophenyl)-porphyrin ($T_4$-APP) to form the colored chelates which were then enriched by solid phase extraction with $C_{18}$ cartridge. The enrichment factor of 50 was achieved by eluted the retained chelates from the cartridge with tetrahydrofuran (THF). The chelates were separated on a ZORBAX Stable Bound microcolumn ($2.0{\times}50\;mm,\;1.8\;{\mu}m$)with methanol-tetrahydrofuran (95 : 5, v/v, containing 0.05 mol/L pyrrolidine-acetic acid buffer salt, pH = 10.0) as mobile phase at a flow rate of 0.5 mL/min and detected with a photodiode array detector from 350-600 nm. The seven chelates were separated completely within 2.0 min. The detection limits of lead, cadmium, mercury, nickel, cobalt, silver and tin are 4 ng/L, 3 ng/L, 6 ng/L, 5 ng/L, 5 ng/L, 6 ng/L, 4 ng/L respectively in the original samples. This method was applied to the determination of the seven transition metal in water and food samples with good results.