• Food Science and Preservation
• /
• v.5 no.1
• /
• pp.13-21
• /
• 1998

Korean medicinal herb extracts(KMHE) were applied to the preservation of greenhouse produce in order to prove their effectiveness. KMHE showed remarkable antimicrobial effects against Bacillus cereus, Peudomonas syringae, and Corynebacterium xerosis causing the postharvest decay of greenhouse produce. Among KMHE the extracts of Rheum palmatum L. and Coptis chinensis Franch most obviously inhibited the growth of microorganims causing the Postharvest decay of greenhouse produce, which destroyed to undetectable levels when treated with more than 500ppm of KMHE. The activities of KMHE were stable in the wide spectrum of pH and temperature. Direct visualization of microbial cells by using both transmission electron microscope and scanning electron microscope showed microbial cell membrane the function of which was destroyed by treating with the dilute solutions of KMHE. This change of cellular membrane permeability could be identified in the experiment that O-nitrophenyl-$\beta$-D-galactopyranoside(ONPG), the artificial substrate of $\beta$-galactosidase, was hydrolyzed in the presence of KMHE, indicating that the membrane was perturbed by KMHE.

• Journal of Industrial Technology
• /
• v.24 no.B
• /
• pp.59-64
• /
• 2004

GaAs thin films were grown epitaxially by MOCVD method on (001) GaAs substrate. And as a surfactant, Bi(bismuth) thin films were deposited on GaAs buffer layer by using TMBi(trimethylbismuth) source. In-situ reflectance difference spectroscopy(RDS) was used to monitor the surface reconstruction of GaAs and Bi thin films. As the results, under the exposure of TBAs(tertiarybuthylarsine) and hydrogen atmosphere, the surface reconstruction of GaAs was changed from As-rich c($4{\times}4$) to As-rich ($2{\times}4$), which was due to the adsoption and desorption of As dimers. The first bismuth surface related RDS signal was reported. At the deposition temperature of $450^{\circ}C$, Bi-terminated GaAs surface showed the RDS spectrum similar to that of Sb-terminated GaAs surface, possibly a ($2{\times}4$) surface. And Bi surface layers were rapidly evaporated with increasing the deposition temperature($550^{\circ}C$), finally becoming As-terminated ($2{\times}4$) surface.

• Bulletin of the Korean Chemical Society
• /
• v.29 no.1
• /
• pp.69-75
• /
• 2008

Tautomerism of pyrimidine base cytosine has been comparatively examined on nanoparticle and roughened plate surfaces of silver, gold, and copper by surface-enhanced Raman scattering (SERS). The SERS spectrum was found to be different depending on the metals and their substrate conditions suggesting the dissimilar population of various tautomers of cytosine on the surfaces. The ab initio calculations were performed at the levels of B3LYP, HF, and MP2 levels of theory with the LanL2DZ basis set to estimate the energetic stability of the tautomers with the metal complexes as well as the gas phase state. The amino group and N3-coordinated tautomer was predicted to be more favorable for bonding to Au, whereas the hydroxyl and N1-coordinated zwitter ionic form is most stable with Ag and Cu as a bidentate form from the DFT calculation. The binding energy with the Ag atom is calculated to be smaller than those with the Au and Cu atoms in line with the temperature-dependent SERS spectra of cytosine.

• Journal of the Korean Ceramic Society
• /
• v.42 no.7 s.278
• /
• pp.521-524
• /
• 2005

ZnO 2-D nanowall structure with around 100 nm thickness, which is composed of tens of nm scale ZnO single crystals, was fabricated through the low temperature chemical solution growth method. Electro Chemical Deposition (ECD) technique was applied to attach the ZnO seed crystals on ITO coated glass substrate. The ZnO nanowall structure was grown in the 0.015 mol$\%$ of aqueous solution of zinc nitrate and hexamethenamine at 60$^{\circ}C$ for 20 - 40 h. The nanowall structure depends on the ECD condition or the applied voltage and duration time. The nanowall shows a photoluminescence around 550 - 700 nm spectrum range.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.378-378
• /
• 2010

The ZnSe epilayers were grown on the GaAs substrate by hot wall epitaxy. After the ZnSe epilayers treated in the vacuum-, Zn-, and Se-atmosphere, respectively, the defects of the epilayer were investigated by means of the low, temperature photoluminescence measurement. The dominant peaks at 2.7988 eV and 2.7937 eV obtained from the PL spectrum of the as-grown ZnSe epilayer were found to be consistent with the upper and the lower polariton peak of the exciton, $I_2$ ($D^{\circ}$, X), bounded to the neutral donor associated with the Se-vacancy. This donor-impurity binding energy was calculated to be 25.3 meV. The exciton peak, $I_l^d$, at 2.7812 eV was confirmed to be bound to the neutral acceptor corresponded with the Zn-vacancy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.380-380
• /
• 2010

The chalcopyrite $ZnIn_2S_4$ epilayers were grown on the GaAs substrate by using a hot-wall epitaxy (HWE) method. The crystal field and the spin-orbit splitting energies for the valence band of the $ZnIn_2S_4$ have been estimated to be 0.1541 eV and 0.0129 eV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}so$ definitely exists in the $\Gamma_5$ states of the valence band of the $ZnIn_2S_4$/GaAs epilayer. The three photocurrent peaks observed at 10 K are ascribed to the $A_{1^-}$, $B_{1^-}$, and $C_1$-exciton peaks for n = 1. Also, we obtained the $A_{\infty^-}$ and B-exciton peaks from the PC spectrum at 293 K.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.25 no.6
• /
• pp.446-450
• /
• 2005

We have built a spherically focused, not using acoustic mirrors, capacitive micromachined air-coupled ultrasonic transducer. A flexible backplate of a copper/polyimide backplate is used, permitting it to conform to a spherically shaped substrate. The backplate is patterned with $40-{\mu}m$ depressions having $80-{\mu}m$ center-to-center spacing. A $6-{\mu}m$ thick aluminized Mylar film completing the transducer is deformed to allow it to conform to the spherical backplate. The device's frequency spectrum is centered at 805kHz with -6dB points at 440 and 1210kHz.

• Transactions on Electrical and Electronic Materials
• /
• v.8 no.5
• /
• pp.191-195
• /
• 2007

We investigated photoluminescence characteristics of ZnO nano needle-like rods grown on a c-plane $AL_2O_3$ substrate by the hot wall epitaxy method. The nano-rods were vertically well aligned along the ZnO c-axis. The diameters of the ZnO nano-rods ranged from 20 nm to 30 nm and their lengths were between 600 and 700 nm. In the photoluminescence spectrum at 10 K, the exciton emission bound to the neutral donor dominated while defect related emission was weakly observed. With a further increase of temperature, the free exciton emission appeared and eventually became dominant at room temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.04b
• /
• pp.25-26
• /
• 2009

We design and demonstrate the controlled morphologies of Ag-dpped ZnO nanowires (NWs) adopting self-contrived hot-walled pulsed laser deposition (HW-PLD). p-type Ag-doping is ensuired by low temperature photoluminescence (PL) spectrum to find the AoX peak at 3.349 eV. Morphology of grown NWs are controlled by changing the kinetic energy and flux of the ablated particles with adjusting the target - substrate (T-S) distance. The analysis on the resultant NWs is presented.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.1150-1151
• /
• 2008

Titanium-doped indium oxide (ITiO) films were prepared on soda-lime glass substrate using a magnetic null discharge (MND) sputter source. The ITiO thin films containing 10 wt.% Ti showed the minimum resistivity of ${\rho}=5.5{\times}10^{-3}{\Omega}cm$. The optical transmittance increases from 70% at 450 nm to 80% at 700 nm in visible spectrum. The surface roughness of the sample showed a change from 10 nm to 50 nm. The ITiO film used for TCO layer of DSCs exhibited an energy conversion efficiency of about 3.8 % at light intensity of 100 $mW/cm^2$.