• Membrane and Water Treatment
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• v.1 no.2
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• pp.139-158
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• 2010

This work focuses on the application of nanofiltration (NF) to the concentration of a pharmaceutical product, Clavulanate ($CA^-$), from clarified fermentation broths, which show a complex composition with six main identified ions ($K^+$, $Cl^-$, ${NH_4}^+$, $H_2{PO_4}^-$, ${SO_4}^{2-}$ and $CA^-$), glucose and glycerol. The solutes transport through the NF membrane pores was investigated using the SEDE (Steric, Electric and Dielectric Exclusion) model. This model was applied to predict the rejection rates of the initial feed solution and the final concentrated solution (10-fold concentrated solution). The best results were achieved with a single fitted parameter, ${\varepsilon}_p$ (the dielectric constant of the solution inside pores) and considering that the membrane selectivity is governed by steric, electric (Donnan) and Born dielectric exclusion mechanisms. While the predicted intrinsic rejections of solutions comprising up to six ions and uncharged solutes were in good agreement with the experimental values, the deviations were much larger for the 10-fold concentrated solution.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4361-4365
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• 2011

The nucleophilic substitution reactions of bis(N,N-dimethylamino) phosphinic chloride (3) with substituted anilines ($XC_6H_4NH_2$) and deuterated anilines ($XC_6H_4ND_2$) are investigated kinetically in acetonitrile at $65.0^{\circ}C$. The anilinolysis rate of 3 is rather slow to be rationalized by the conventional stereoelectronic effects. The magnitudes of ${\rho}_X$ (= -6.42) and ${\beta}_X$ (= 2.27) values are exceptionally great. The deuterium kinetic isotope effects (DKIEs; $k_H/k_D$) are secondary inverse ($k_H/k_D$ = 0.69-0.96). A concerted $S_N2$ mechanism involving a backside attack is proposed on the basis of secondary inverse DKIEs and the variation trend of the $k_H/k_D$ values with X. The anilinolyses of six phosphinic chlorides in MeCN are briefly reviewed by means of DKIEs, steric effects of the two ligands, positive charge of the reaction center phosphorus atom, and selectivity parameters to obtain systematic information on phosphoryl transfer reaction mechanism.

• Textile Coloration and Finishing
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• v.27 no.4
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• pp.261-269
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• 2015

Two new D-${\pi}$-A dyes were synthesized by the condensation reaction between active methyl and aromatic aldehyde and its biothiol sensing properties in DMSO/water were investigated by UV-vis spectroscopy. Upon addition of $Hg^{2+}$, the solution of D-${\pi}$-A dyes showed color change and the absorption band shows a formation of a dye-$Hg^{2+}$ coordination complex. These dyes exhibited high selectivity for $Hg^{2+}$ as compared with other cations. The dye-$Hg^{2+}$ could be recovered by adding glutathion(GSH). The absorption intensity of dye-$Hg^{2+}$ increased only by the addition of glutathione(GSH). The competition experiments revealed that no obvious interference was observed by performing the titration with the mixture of glutathione(GSH) and other amino acids. The results indicated that these D-${\pi}$-A dyes were highly selective for glutathione(GSH) detection.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.1
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• pp.24-29
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• 2004

$CF_4$ gas is one of the most useful gases in modern technologies for semiconductor fabrication. However, there are many problems which should be solved in order to fabricate semiconductor device, for example, etching speed drop due to ion charge-up and etching selectivity drop due to the high electron energy. One of useful method in order to suppress their damages above is pulsed-time modulated plasma (PM). However, transient responses of charged particles occur when the source power is turned-on and -off in PM method. To control plasma properties in detail, such a transient phenomenon must be investigated. In this paper, we investigate $CF_4$ RF plasma properties under a one-dimensional fluid model. And also for dynamic and stable control of $CF_4$ plasmas, we investigated the transient behavior of the plasmas after step up or down of the amplitude of the power source voltage $V_s$(t). Fundamental properties of transient $CF_4$ plasmas was discussed. Furthermore, we intend to discuss new method for pulsed-time plasma modulation.

• KSBB Journal
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• v.8 no.4
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• pp.370-374
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• 1993

In transportation the amount of metal ion by crown ethers, dibenzo-18-crown-6 were investigated using ultraviolet spectrometer. Transported the amount of one valence metal ion as $K^+ and Li^+}$ was not so much. On the other hand, two valence metal ion increased by dibenzo-18-crown-6, which means that the ionic charge and hydration of two valence metal ion affected the carrying ability of crown ethers. The carrying ability of dibenzo-18-crown-6 was, therefore, adequate for two valence metal ion as $Ca^{2+}$ and $Ba^{2+}$. It was also suggested that transport metal ion by crown ethers, which is related rather the catching ability than the selectivity of metalion.

• Journal of Electrical Engineering and Technology
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• v.4 no.1
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• pp.106-110
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• 2009

An amperometric glucose biosensor has been developed using viologen derivatives as a charge transfer mediator between a glucose oxidase (GOD) and a gold electrode. A highly stable self-assembled monolayer (SAM) of thiol-based viologen was immobilized onto the gold electrode of a quartz crystal microbalance (QCM) and GOD was immobilized onto the viologen modified electrode. This biosensor response to glucose was evaluated amperometrically in the potential of -300mV. Upon immobilization of the glucose oxidase onto the viologen modified electrode, the biosensor showed rapid response towards glucose. Experimental conditions influencing the biosensor performance, such as pH potential, were optimized and assessed. This biosensor offered excellent electrochemical responses for glucose concentration below ${\mu}$ mol level with high sensitivity and selectivity and short response time. The levels of the RSDs (<5%) for the entire analyses reflected the highly reproducible sensor performance. A linear calibration range between the current and the glucose concentration was obtained up to $4.5{\times}10^{-4}M$. The detection limit was determined to be $3.0{\times}10^{-6}M$.

• Journal of Soil and Groundwater Environment
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• v.14 no.1
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• pp.29-35
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• 2009

In this study, the effect of pH and temperature on the adsorption behavior of acid mine drainage (AMD) on coal mine drainage sludge (CMDS) has been investigated during the treatment of coal mine drainage (CMD) by electrical purification method. The pH$_{zero\;point\;charge}$ (pH$_{zpc}$) of CMDS was 5. The removal ratio of copper, zinc, cadmium, iron were increased according to the increase of pH value. The adsorption amount of copper showed 0.64 mg g$^{-1}$ sludge. It was independent of pH value. The adsorption amount of the other metals showed l.l times when pH was 3. The adsorption amount of chromium was a little bit increased at the pH value higher than 7 due to a small amount of the chromium was eluted as $Cr(OH)_6^{3-}$. The amount of metals' absorption were decreased according to temperature was increase at pH value was 3. The selectivity order was Cd>Fe > Zn > Cu. The amount of absorption showed q$_{max}$ Cu 2.747 mg g$^{-1}$ andZn 2.525 mg g$^{-1}$ when pH value higher than 5. It was independent of temperature.

• Korean Journal of Materials Research
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• v.12 no.11
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• pp.860-864
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• 2002

$Li^{+}$ extraction reactions with ion-exchange type lithium manganese oxide in an aqueous phase were examined using chemical and x-ray diffraction (XRD) analysis. In the process of extraction reaction, the lithium manganese oxide showed a topotactic extraction of $Li^{+ }$ in the aqueous phase mainly through an ion-exchange mechanism, and the $Li^{+}$ extracted samples indicated a high selectivity and a large capacity for $Li^{+}$ . The electronic structures and chemical bonding properties were also studied using a discrete variational (DV)-X$\alpha$ molecular orbital method with cluster model of (Li$Mn_{12}$ $O_{40}$ )$^{27-}$ for tetrahedral sites and ($Li_{7}$ Mn $O_{38}$ )$^{3}$ for octahedral site in $Li_{1.33}$ $Mn_{1.67}$ / $O_{4}$ respectively. Li in the manganese oxides is highly ionized in both sites, but the net charge of Li was greater for tetrahedral sites than octahedral. These calculations suggest that the tetrahedral sites have higher $Li^{+}$ $H^{+}$ exchangeability than the octahedral sites, and are preferable for the selective adsorption for L $i^{+}$ ions.s.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.400.1-400.1
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• 2016

Interfacial engineering approaches as an efficient strategy for improving the power conversion efficiencies (PCEs) of inverted polymer solar cells (iPSCs) has attracted considerable attention. Recently, polymer surface modifiers, such as poly(ethyleneimine) (PEI) and polyethylenimine ethoxylated (PEIE), were introduced to produce low WF electrodes and were reported to have good electron selectivity for inverted polymer solar cells (iPSCs) without an n-type metal oxide layer. To obtain more efficient solar cells, quantum dots (QDs) are used as effective sensitizers across a broad spectral range from visible to near IR. Additionally, they have the ability to efficiently generate multiple excitons from a single photon via a process called carrier multiplication (CM) or multiple exciton generation (MEG). However, in general, it is very difficult to prepare a bilayer structure with an organic layer and a QD interlayer through a solution process, because most solvents can dissolve and destroy the organic layer and QD interlayer. To present a more effective strategy for surpassing the limitations of traditional methods, we studied and fabricated the highly efficient iPSCs with mono-layered QDs as an effective multi-functional layer, to enhance the quantum yield caused by various effects of QDs monolayer. The mono-layered QDs play the multi-functional role as surface modifier, sub-photosensitizer and electron transport layer. Using this effective approach, we achieve the highest conversion efficiency of ~10.3% resulting from improved interfacial properties and efficient charge transfer, which is verified by various analysis tools.

• Journal of the Korean Chemical Society
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• v.51 no.4
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• pp.324-330
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• 2007

A new ion selective PVC membrane electrode is developed as a sensor for mercury(II) ions based on bis(benzoylacetone) propylenediimine (H2(BA)2PD) as an ionophore. The electrode shows good response characteristics and displays, a linear Emf vs. log[Hg2+] response over the concentration range of 1.0×10-6 to 1.0×10-1 M Hg(II) with a Nernstian slope of 29.8±0.75 mV per decade and with a detection limit of 2.2×10-7 M Hg(II) over the pH range of 2.5-11.5. Selectivity concentrations for Hg(II) relative to a number of potential interfering ions were also investigated. The sensor is highly selective for Hg(II) ions over a large number of cations with different charge. The sensor has been found to be chemically inert showing a fast response time of 60 s and was used over a period of 3 months with a good reproducibility (S = 0.27 mV). The electrode was successfully applied to determine mercury(II) in real samples with satisfactory results.