• KSBB Journal
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• v.16 no.6
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• pp.562-567
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• 2001

Aspergillus niger LK harboring the enantioselective epoxide hydrolase (EHase) activity was isolated, and enantioselectivity of EHase was tested for various racemic aromatic epoxides. The gene encoding epoxide hydrolase was cloned from cDNA library generated by reverse transcriptase-polymerase chain reaction of the isolated total mRNA. Sequence analysis showed that the cloned gene encodes 398 amino acids with a deduced molecular mass of 44.5 kDa. Database comparison of the amino acid sequence reveals that it is similar to fungal EHase, whereas the sequence identity with bacterial EHase is very low. Recombinant expression of the cloned EHase in Escherichia coli BL21 yielded an active EHases, which can offer a potential biocatalyst for the production of chiral epoxides.

• Korean Journal of Crystallography
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• v.14 no.1
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• pp.1-6
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• 2003

NiZn-ferrites were synthesized from the waste catalysts. which were by product of styrene monomer process and buried underground as an industrial wastes, and their magnetic properties were investigated. Nickel oxide and zinc oxide powders were mixed with finely ground waste catalysts, and spinel type ferrite was obtained by calcination at 900℃ and sintering at 1325℃ for 5 hours. The initial permeabilities were measured and reflection losses were calculated from S-parameters for the composition of Ni/sub x/Zn/sub 1-x/Fe₂O₄(x=0.36, 0.50, 0.66) and (Ni/sub 0.5/Zn/sub 0.5)/sub 1-y/Fe/sub 2+y/O₄(y=-0.02, 0, 0.02).

• Polymer(Korea)
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• v.39 no.3
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• pp.468-474
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• 2015

Electrically conductive polymer nanocomposites were prepared by the inclusion of graphene-based nanofillers. Graphene oxide (GO) and reduced graphene oxide wrapped by poly(styrene sulfonate) (PSS-RGO) were used as nanofillers to make good dispersion with the aqueous dispersion of polystyrene (PS) particles. GO sheets were synthesized by the modified Hummers' method from graphite, and PSS-RGO sheets were prepared by the reduction of GO-dispersed PSS solution with hydrazine monohydrate. Morphology and properties of PS/GO and PS/PSS-RGO nanocomposites via latex technology were investigated. Both nanofillers showed well dispersed morphology in PS matrix. Rheological and electrical percolation thresholds were 0.28 and 0.51 wt% for GO, and 0.50 and 1.01 wt% for PSS-RGO respectively. It is speculated that PS/GO nanocomposites showed better conductivity than PS/PSS-RGO counterparts due to the partial recovery of GO by thermal reduction during molding.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.3 s.36
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• pp.213-217
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• 2005

The polymer light emitting diodes (PLED) with ITO/PEDOT:PSS/MEH-PPV/Al structure were prepared on ITO(indium tin oxide)/Glass substrates using PEDOT:PSS[poly(3,4-ethylenedioxythiophene):poly(styrene sulfolnate)] as the hole transport material and MEH-PPV[poly(2-methoxy-5-(2-ethyhexoxy)-1,4phenylenvinylene)] as emission material layer. The dependences on the surface roughnees and friction coefficient between film layers were investigated as a function of the MEH-PPV concentrations$(0.1\;wt\%\~0.9\;wt\%)$. The RMS values decreased from 1.72 nm to 1.00 nm as the concentration of MEH-PPV increased from $0.1\;wt\%\;to\;0.9\;wt\%$, indicating improvement of surface roughness. In addition, friction coefficients decreased from 0.048 to 0.035, which means the deteriorating of the adhesion condition. The PLED sample with $0.5\;wt\%$ of MEH-PPV showed the maximum luminance of $409\;cd/m^2$.

• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.663-669
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• 1992

Chromium oxide/zirconia catalysts were prepared by dry impregnation of $Zr(OH)_4$ powder with aqueous solution of $(NH_4)_2CrO_4$ followed by calcining in air. The redox behavior of prepared catalysts were investigated by reacting cumene as test material over catalysts. As a result it was found that $Cr^{6+}$ species(as chromate) on the surface of catalyst was responsible for the formation of strong acid site and the catalytic activity for the dealkylation of cumene. However, much of the $Cr^{6+}$ species was reduced to $Cr^{3+}$ species by $H_2$ formed during the catalytic reaction of cumene and the reduced $Cr^{3+}$ species was an active site for dehydrogenation of cumene to form ${\alpha}$-methyl styrene. The reduced $Cr^{3+}$ species was also reoxidized to a $Cr^{6+}$ species after treatment with $O_2$ and consequently the deoxidized catalyst exhibited catalytic activity for the dealkylation reaction of cumene.

• Resources Recycling
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• v.10 no.3
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• pp.23-28
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• 2001

Zinc ion could be recovered from metal plating wastewater with the spent iron oxide catalyst which was used in the plant of Styrene Monomer(SM) production. The zinc was recovered more than 98.7% at higher than pH 2.0. The saturation magnetization of the spent catalyst is enough high as 59.4 emu/g to apply in the solid-liquid separation after treating the wastewater. The mechanism of zinc recovery with the iron oxide catalyst could be a electro-chemical adsorption at pH 3.0~8.5, and a precipitation as $Zn(OH)_2$ at higher than pH 8.5.

• Journal of the Korean Magnetics Society
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• v.15 no.1
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• pp.37-41
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• 2005

We prepared water-based magnetic fluids with the spent iron oxide catalysts which were used in the styrene monomer production process. The catalyst was composed with 70% magnetite and alkali metals. The water-based magnetic fluids were prepared by mechanical grinding with olecic acid as a surfactant and water in an attritor. The magnetization of the water-based magnetic fluids was 22 emu/g in the 10 kOe.

• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.173-177
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• 2015

In this study, effects of both the grafted ABS-g-MAH and the added graphene oxide (GO) on the impact strength of polycarbonate (PC)/poly(acrylonitrile-butadiene-styrene) (ABS) blends were discussed. The PC/ABS blends and PC/ABS/GO composites were fabricated by using twin screw extruder with ABS-g-MAH as a compatibilizer. The ABS-g-MAH was prepared by melting extrusion of ABS and maleic anhydride (MAH) with DCP (dicumyl peroxide) as an initiator using twin screw extruder and the synthesis of ABS-g-MAH was confirmed by the presence of carbonyl group (C=O) peak at $1780cm^{-1}$ of FT-IR spectrum. According to the thermal, rheological, and impact properties of PC/ABS blends, 5 phr (parts per hundred resin) of compatibilizer was chosen as an optimum content for the PC/ABS/GO composites. It was observed that the thermal decomposition of ABS/PC/GO composites increased with GO contents, but there was no significant changes or a decrease in the impact strength. Also the composite fabricated by ABS/GO showed small increase in the impact strength. From the result of the dynamic rheometer to observe the processing properties, the complex viscosities of PC/ABS blend including the compatibilizer increased, but the complex viscosities of composites added GO were not changed.

• Applied Chemistry for Engineering
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• v.26 no.6
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• pp.640-647
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• 2015

As the need for next-generation flexible electronics grows, novel materials and technologies that can replace conventional indium tin oxide (ITO) for transparent electrodes have been of great interest. Among them, a conducting polymer, especially poly(3,4-ethylenedioxythiophene) : poly(styrene sulfonate) (PEDOT : PSS) is one of the most promising candidates because it is mechanically flexible, inexpensive, and capable of being processed in solution. Currently, there are a lot of research efforts on enhancing its electrical conductivity to the level of ITO or metal electrodes through chemical and/or physical processing. In this review article, we present various additives and pre-/post-deposition processing methods for improving the electrical conductivity of PEDOT : PSS. Some of representative reports are also introduced, which demonstrated the use of conductivity-enhanced PEDOT : PSS as transparent electrodes in electronics and energy conversion.

• Applied Chemistry for Engineering
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• v.27 no.4
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• pp.402-406
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• 2016

In order to investigate the thermal stability of electro-conductive poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT/PSS), we have prepared films by casting PEDOT/PSS aqueous solution without using a binding material and measured surface resistances of the films while annealing at $200^{\circ}C$. Electrical properties of films were improved by annealing, and the maximum conductivity ($540S{\cdot}m^{-1}$) after annealing for 2 hrs was found to be approximately 3 times higher than that ($180S{\cdot}m^{-1}$) of the original film. The conductivities, however, dramatically decreased with an increase in annealing time and dissipated after 24 hrs of annealing. On the other hand, PEDOT/PSS films hybridized with graphene oxide (GO) displayed a salient improvement in conductivity by annealing, which was measured to be around $600S{\cdot}m^{-1}$ even after 30 hrs of annealing at $200^{\circ}C$. We tentatively conclude that hybridization with GO enhances the thermal stability of PEDOT/PSS.