• Journal of the Korean Electrochemical Society
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• v.2 no.1
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• pp.31-37
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• 1999

Copper-containig enzyme, laccase (Rhus vernicifera) was immobilized onto gold electrode using self-assembly technique and its surface properties and catalytic activities were examined. Laccase is an oxidoreductase capable to oxidize diphenols or diamines by 4-electron reduction of molecular oxygen without superoxide or peroxide intermediates. The electrode surface were modified by $\beta-mercaptopropionate$ to have a net negative charge in neutral solution and positively charged laccase (pI=9) was immobilized by electrostatic interaction. The successful immobilization was confirmed by cyclic voltammograms which showed typical surface-confined shapes and behaviors. The amount of charge to reduce the surface was similar to the charge calculated assuming the surface being covered by monolayer. The activity of the immobilized enzyme was tested by the capbility of oxidizing a substrate, ABTS (2,2-azine-bis-(3-ethylbenzthioline-6-sulfonic acid) and it was maintained for $2\~3$ days at $4^{\circ}C$. The immobilzed laccase showed about $10\~15\%$ activity compared to that in solution. The laccase-modified electrode showed the activity of elefoocatalytic reduction of oxygen in the presence of mediator, $Fe(CN)_6^{3-}$ The addtion of azide which is an inhibitor of laccase compeletly eliminated the catalytic current.

• Polymer(Korea)
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• v.25 no.2
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• pp.186-198
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• 2001

pH/Thermal sensitive copolymers with the various acidic comonomer compositions composed of N-isopropylacrylamide (NIPAAm) with acrylic acid (AAc), 2-acrylamido glycolic acid (AAmGAc), and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) were synthesized by free radial polymerization. In this study, to characterize the effect of different acidic comonomer composition and pH on the lower critical solution temperature (LCST) behaviors of their copolymers. phase transition experiments were performed with a thermo-optical analyzer (TOA). The phase transition temperature (T$^{p}$ ) of aqueous poly(NIPAAm-co-AAc) solution was lowered with increasing the ionization of the acid group in AAc, that is, the ionized state induced the electrostatic repulsion of ionized groups. In contrast, when AAmGAc was introduced into PNIPAAm, T$^{p}$ was little changed at pH 1-3, whereas climbed up significantly from pH 1 to pH 3. In the range of pH 6-10, Tp was lower than that of pH 3-5. This result was considered to be \"Ionic Screen Effect\" and this effect had been also observed in the case of poly(NIPAAm-co-AMPS).-co-AMPS).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.546-546
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• 2008

Copper (Cu) Chemical mechanical polishing (CMP) has been an essential process for Cu wifing of DRAM and NAND flash memory beyond 45nm. Copper has been employed as ideal material for interconnect and metal line due to the low resistivity and high resistant to electro-migration. Damascene process is currently used in conjunction with CMP in the fabrication of multi-level copper interconnects for advanced logic and memory devices. Cu CMP involves removal of material by the combination of chemical and mechanical action. Chemicals in slurry aid in material removal by modifying the surface film while abrasion between the particles, pad, and the modified film facilitates mechanical removal. In our research, we emphasized on the role of chemical effect of slurry on Cu CMP, especially on the effect of amine functional group on removal rate selectivity between Cu and Tantalum-nitride (TaN) film. We investigated the two different kinds of complexing agent both with amine functional group. On the one hand, Polyacrylamide as a polymer affected the stability of abrasive, viscosity of slurry and the corrosion current of copper film especially at high concentration. At higher concentration, the aggregation of abrasive particles was suppressed by the steric effect of PAM, thus showed higher fraction of small particle distribution. It also showed a fluctuation behavior of the viscosity of slurry at high shear rate due to transformation of polymer chain. Also, because of forming thick passivation layer on the surface of Cu film, the diffusion of oxidant to the Cu surface was inhibited; therefore, the corrosion current with 0.7wt% PAM was smaller than that without PAM. the polishing rate of Cu film slightly increased up to 0.3wt%, then decreased with increasing of PAM concentration. On the contrary, the polishing rate of TaN film was strongly suppressed and saturated with increasing of PAM concentration at 0.3wt%. We also studied the electrostatic interaction between abrasive particle and Cu/TaN film with different PAM concentration. On the other hand, amino-methyl-propanol (AMP) as a single molecule does not affect the stability, rheological and corrosion behavior of the slurry as the polymer PAM. The polishing behavior of TaN film and selectivity with AMP appeared the similar trend to the slurry with PAM. The polishing behavior of Cu film with AMP, however, was quite different with that of PAM. We assume this difference was originated from different compactness of surface passivation layer on the Cu film under the same concentration due to the different molecular weight of PAM and AMP.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.184-188
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• 2008

This study presented simple and efficient fabrication of chemical sensors for the detection of acidic gas using 1,3-bisdicyanovinylindane as an indicator because it can be promising materials having property of the rapid color change according to the variation of pH. The dissociation of proton and dye in acidic condition as changing of ion pairs give rise to dramatically change the absorbance intensity of 1,3-bisdicyanovinylindane, which can be easily applied to the development of chemical sensors. In addition, indicator dyes having negatively charge in aqueous phase can be easily fabricated using layer-by-layer (LBL) methods by way of electrostatic interaction. For the proof of concept, we demonstrated the abrupt presentation of skeleton symbol on the chemical sensor, which could be resulted from the reaction of 1,3-bisdicyanovinylindane as background color with acidic gas. Thus, the rapid appearance of symbol will induce user's caution under the emergency condition. The presented chemical gas sensor using 1,3-bisdicyanovinylindane have strong advantages. First, the fabrication process of gas sensor was very simple and low-cost. Secondly, sensors reacted by acidic gas could be reused for several times. Finally, the chemical gas sensor would be environmentally friend, which can be a basic tool for the realization of eco-organic sensor device.

• Journal of the Korean Chemical Society
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• v.30 no.4
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• pp.335-450
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• 1986

The thermodynamic dissociation constants of $[Co(en)]_3Cl_3\;and\;[Co(NH_3)_6Cl_3$ in aqueous solutions at $25{\circ}$ and at the pressure from 1 bar to 2000 bars were measured by conductometric method. The dissociation constants were increased with pressure elevation because of volume decreasing by the formation of charged ions during dissociation reaction. That is, the $pK^T$ values of $[Co(en)]_3Cl_3$ were 2.16 for I bar, 2.08 for 500 bars, 2,08 for 1000 bars, 2.05 for 1500 bars and 2.03 for 2000 bars, respectively and those of $[Co(NH_3)_6Cl_3$ were 2.02 for 1 bar 1.96 for 500 bars, 1.90 for 1000 bars, 1. 88 for 1500 bars and 1. 87 for 2000 bars, respectively. Comparing and analyzing the values of Stokes' radii and $K^T$, the formation of ion pair compound was affected by not only the electrostatic interaction, but also the Interal Conjugate Base(ICB), which was increased by the elevation of the pressure.

• Journal of the Korean Chemical Society
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• v.32 no.3
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• pp.171-178
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• 1988

The potential energy of adsorbate molecules in the main channel of $K^+$ ion exchanged zeolite L(K-L) was calculated. In K-L which adsorbs three molecules per unit cell, the interaction energies of $H_2O,\;NH_3,\;CH_3NH_2,\;(CH_3)_2NH,\;and\;(CH_3)_3N$ molecules with zeolite lattice are 61.11, 62.31, 65.68, 74.65, and 79.88kJ/mol, respectively. These values are less by 3.7∼12.6kJ/mol than $K^+$ ion affinities with adsorbing molecules. These results may be due to the facts that the electrostatic energies are reduced by the negative charge of the lattice oxygens. The distribution of adsorption sites of $NH_3$ and $CH_3NH_2$ in K-L was investigated by a technique of temperature programmed desorption. The experimental value of desorption energies of $NH_3$ and $CH_3NH_2$ on K-L are in good agreement with the theoritical values. It is concluded that the desorption of $NH_3$ and $CH_3NH_2$ on K-L is the first-order desorption with free readsorption.

• Applied Chemistry for Engineering
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• v.32 no.6
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• pp.684-689
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• 2021

In this paper, we develop a cost effective and disposable voltammetric sensing platform involving screen-printed carbon electrode (SPCE) modified with the nanocomposites composed of multi-walled carbon nanotubes, polyelectrolyte, and tyrosinase for bisphenol A. This is known as an endocrine disruptor which is also related to chronic diseases such as obesity, diabetes, cardiovascular and female reproductive diseases, precocious puberty, and infertility. A negatively charged oxidized multi-walled carbon nanotubes (MWCNTs) wrapped with a positively charged polyelectrolyte, e.g., polydiallyldimethylammonium, was first wrapped with a negatively charged tyrosinae layer via electrostatic interaction and assembled onto oxygen plasma treated SPCE. The nanocomposite modified SPCE was then immersed into different concentrations of bisphenol A for a given time where the tyrosinase reacted with OH group in the bisphenol A to produce the product, 4,4'-isopropylidenebis(1,2-benzoquinone). Cyclic and differential pulse voltammetries at the potential of -0.08 V vs. Ag/AgCl was employed and peak current changes responsible to the reduction of 4,4'-isopropylidenebis(1,2-benzoquinone) were measured which linearly increased with respect to the bisphenol A concentration. In addition, the SPCE based sensor showed excellent selectivity toward an interferent agent, bisphenol S, which has a very similar structure. Finally, the sensor was applied to the analysis of bisphenol A present in an environmental sample solution prepared in our laboratory.

• Korean Chemical Engineering Research
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• v.57 no.1
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• pp.1-4
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• 2019

In this study, an anthracene cross-linker is introduced to enhance the catalytic activity of glucose oxidase (GOx) based catalysts and to increase the amount of enzyme loading. The crosslinked GOx is bonded with the CNT/PEI support using the electrostatic interaction (AC[CNT/PEI/GOx]). Electrochemical evaluations are done to evaluate the performance of this catalyst and the performance of CNT/PEI/GOx catalyst is also measured as a control. According to the measurements, it is confirmed that the amount of loaded GOx increases, while $K_m$ value calculated by Lineweaver-Burk plot shows that AC[CNT/PEI/GOx] ($K_m$ : 0.73 mM) is superior to CNT/PEI/GOx ($K_m$ : 1.71 mM) without cross-linking reaction. Based on these effects, it is demonstrated that the maximum power density of the enzymatic biofuel cell using AC[CNT/PEI/GOx] increases from $21.2{\mu}W/cm^2$ to $57.4{\mu}W/cm^2$.

• Clean Technology
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• v.27 no.2
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• pp.115-123
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• 2021

This study demonstrates a new method for the synthesis of organic-inorganic hybrid particles composed of an inorganic silica shell and organic core particles. The organic core particles are prepared with a uniform size using droplet-based microfluidic technology. In the process of preparing the organic core particles, uniform droplets are generated by independently controlling the flow rates of the dispersed phase containing photocurable resins and the continuous phase. After the generation of droplets in a microfluidic device, the droplets are photo-polymerized as particles by ultraviolet irradiation at the ends of microfluidic channels. The core particle is coated with a nano complex composed of polyallylamine hydrochloride (PAH) and phosphate ion (Pi) through strong non-covalent interactions such as hydrogen bonding and electrostatic interaction under optimized pH conditions. The polyamine nano complex rapidly induces the condensation reaction of silicic acid through the arranged amine groups of the main chain of PAH. Therefore, this method enabled the preparation of organic-inorganic hybrid particles coated with inorganic silica nanoparticles on the organic core. Finally, we demonstrated the synthesis of organic-inorganic hybrid particles in a short time under ambient and environmentally friendly conditions, and this is applicable to the production of organic-inorganic hybrid particles having various sizes and shapes.

• Applied Chemistry for Engineering
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• v.32 no.3
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• pp.312-319
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• 2021

Photothermal therapy is a treatment that necrotizes selectively the abnormal cells, in particular cancer cells, which are more vulnerable to heat than normal cells, using the heat generated when irradiating light. In this study, we synthesized a reduced graphene oxide with carboxyl groups (CRGO)-gold nanorod (AuNR) nanocomposite for photothermal treatment. Graphene oxide (GO) was selectively reduced and exfoliated at high temperature to synthesize CRGO, and the length of AuNR was adjusted according to the amount of AgNO₃, to synthesize AuNR with a strong absorption peak at 880 nm, as an ideal photothermal agent. It was determined through FT-IR, thermogravimetric and fluorescence analyses that more carboxyl groups were conjugated with CRGO over RGO. In addition, CRGO exhibited excellent stability in aqueous solutions compared to RGO due to the presence of carboxylic acid. The CRGO-AuNR nanocomposites fabricated by electrostatic interaction have an average size of ~317 nm with a narrow size distribution. It was confirmed that under radiation with a near-infrared 880 nm laser which has an excellent tissue transmittance, the photothermal effect of CRGO-AuNR nanocomposites was greater than that of AuNR due to the synergistic effect of the two photothermal agents, CRGO and AuNR. Furthermore, the results of cancer cell toxicity by photothermal effect revealed that CRGO-AuNR nanocomposites showed superb cytotoxic properties. Therefore, the CRGO-AuNR nanocomposites are expected to be applied to the field of anticancer photothermal therapy based on their stable dispersibility and improved photothermal effect.