• Bulletin of the Korean Chemical Society
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• 제32권6호
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• pp.1951-1956
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• 2011

A kinetic study is reported on nucleophilic substitution reactions of 4-nitrophenyl nicotinate 5 and isonicotinate 6 with alkali metal ethoxide EtOM (M = K, Na, and Li) in anhydrous ethanol at $25.0{\pm}0.1^{\circ}C$. Plots of pseudo-first-order rate constant $k_{obsd}$ vs. EtOM concentration exhibit upward curvature for the reactions of 5 and 6 with EtOK and EtONa but are almost linear for those with EtOLi. Dissection of $k_{obsd}$ into $k_{EtO^-}$ and $k_{EtOM}$ (i.e., the second-order rate constant for the reaction with dissociated $EtO^-$ and ion-paired EtOM, respectively) has shown that $k_{EtOK}$ ${\geq}$ $k_{EtONa}$ > $k_{EtO^-}$ but $k_{EtOLi}$ < $k_{EtO^-}$. It has been concluded that $K^+$ and $Na^+$ ions catalyze the reactions by increasing the electrophilicity of the carbonyl carbon atom through formation of a 4-membered cyclic transition state $TS_3$ or $TS_4$. However, $M^+$ ion catalysis has been found to be much less significant for the reactions of 5 and 6 than for the corresponding reactions of 4-nitrophenyl picolinate 4, which was reported to proceed through a 5-membered cyclic transition state $TS_2$. Although 5 and 6 are significantly more reactive than 4-nitrophenyl benzoate 3, the reactions of 5 and 6 result in smaller $k_{EtOK}/k_{EtO^-}$ ratios than those of 3. The electron-withdrawing ability of the nitrogen atom in the acyl moiety of 5 and 6 has been suggested to be responsible for the increase in reactivity and the decrease in the $k_{EtOK}/k_{EtO^-}$ ratio.

• 분석과학
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• 제8권2호
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• pp.187-193
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• 1995

N,N,N,N-Tetrabenzylethylenediamine 중성운반체를 이용하여 PVC 수소이온 선택성 막전극을 제조하였다. 가소제 종류(phthalates와 sebacate) 및 친지방성 첨가제(NaTPB)에 따른 막전극의 전기저항과 수소이온 감응범위 및 알칼리금속과 알칼리토금속의 존재하에서 방해효과를 조사하였다. 가소제 종류에 의한 전기저항은 영향을 거의 받지 않았고 NaTPB 0.7%의 경우 수소이온에 대한 Nernstian 기울기는 가장 이론값에 근접하였으며, 또한 알칼리금속 및 알칼리토금속에 의한 방해도 적게 받았다. pH-선택성 고분자 막전극은 pH 2~10 범위내에서 선형적이고, 산과 알칼리용액 중에서 안정성 및 재현성 시험 결과 매우 좋게 나타났다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.292-292
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• 2007

To apply PDP panel, Soda lime glass(SLG) is cheeper than Non-alkali glass and PD-200 glass but has problems such as low strain temperature and ion diffusion by alkali metal oxide. In this paper suggest the methode that prohibits ion diffusion by deposing barrier layer on SLG. Indium thin oxide(ITO) thin films and barrier layers were prepared on SLG substrate by Rf-magnetron sputtering. These films show a high electrical resistivity and rough uniformity as compared with PD-200 glass due to the alkali ion from the SLG on diffuse to the ITO film by the heat treatment. However these properties can be improved by introducing a barrier layer of $SiO_2\;or\;Al_2O_3$ between ITO film and SLG substrate. The characteristics of films were examined by the 4-point probe, SEM, UV-VIS spectrometer, and X-ray diffraction. GDS analysis confirmed that barrier layer inhibited Na and Ka ion diffusion from SLG. Especially ITO films deposited on the $Al_2O_3$ barrier layer had higher properties than those deposited on the $SiO_2$ barrier layer.

• Bulletin of the Korean Chemical Society
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• 제32권7호
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• pp.2423-2427
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• 2011

Pseudo-first-order rate constants ($k_{obsd}$) have been measured spectrophotometrically for nucleophilic substitution reactions of 3,4-dinitrophenyl diphenylphosphinothioate 9 with alkali metal ethoxides (EtOM, M = Li, Na, K) in anhydrous ethanol at $25.0{\pm}0.1^{\circ}C$. The plot of $k_{obsd}$ vs. [EtOM] is linear for the reaction of 9 with EtOK. However, the plot curves downwardly for those with EtOLi and EtONa while it curves upwardly for the one with EtOK in the presence of 18-crown-6-ether (18C6). Dissection of $k_{obsd}$ into $k_{EtO^-}$ and $k_{EtOM}$ (i.e., the second-order rate constant for the reaction with dissociated $EtO^-$ and ion-paired EtOM, respectively) has revealed that the reactivity increases in the order $k_{EtOLi}$ < $k_{EtONa}$ < $k_{EtO^-}$ ${\approx}$ $k_{EtOK}$ < $k_{EtOK/18C6}$, indicating that the reaction is inhibited by $Li^+$ and $Na^+$ ions but is catalyzed by 18C6-crowned $K^+$ ion. The reactivity order found for the reactions of 9 contrasts to that reported previously for the corresponding reactions of 1, i.e., $k_{EtOLi}$ > $k_{EtONa}$ > $E_{EtOK}$ > $k_{EtO^-}$ ${\approx}$ $k_{EtOK/18C6}$, indicating that the effect of changing the electrophilic center from P=O to P=S on the role of $M^+$ ions is significant. A four-membered cyclic transition-state has been proposed to account for the $M^+$ ion effects found in this study, e.g., the polarizable sulfur atom of the P=S bond in 9 interacts strongly with the soft 18C6-crowned $K^+$ ion while it interacts weakly with the hard $Li^+$ and $Na^+$ ions.

• 한국환경과학회지
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• 제12권4호
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• pp.469-476
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• 2003

In order to examine the pre-treatment effect of crab shell en Pb$^{2+}$ removal by crab shell in aqueous solution, acid and alkali pre-treated crab shell were used. Electron microscopy techniques such as TEM (transmission electron microscopy) and SEM (scanning electron microscopy), and EDX (energy dispersive X-ray) and FTIR (Fourier transform infrared) spectrometry techniques were used to investigate the process of Pb$^{2+}$ removal by acid and alkali pre-treated crab shell. The Pb$^{2+}$ removal by acid pre-treated crab shell was much lower than that by untreated crab shell because of the decrease of CaCO$_3$ from the crab shell. However, the Pb$^{2+}$removal by alkali pre-treated crab shell increased compared to that by untreated crab shell. The results were confirmed by TEM, SEM, EDX and FTIR.nd FTIR.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.187-187
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• 2012

Solution-processed metal-alloy oxides such as indium zinc oxide (IZO), indium gallium zinc oxide (IGZO) has been extensively researched due to their high electron mobility, environmental stability, optical transparency, and solution-processibility. In spite of their excellent material properties, however, there remains a challenging problem for utilizing IZO or IGZO in electronic devices: the supply shortage of indium (In). The cost of indium is high, what is more, indium is becoming more expensive and scarce and thus strategically important. Therefore, developing an alternative route to improve carrier mobility of solution-processable ZnO is critical and essential. Here, we introduce a simple route to achieve high-performance and low-temperature solution-processed ZnO thin film transistors (TFTs) by employing alkali-metal doping such as Li, Na, K or Rb. Li-doped ZnO TFTs exhibited excellent device performance with a field-effect mobility of $7.3cm^2{\cdot}V-1{\cdot}s-1$ and an on/off current ratio of more than 107. Also, in case of higher drain voltage operation (VD=60V), the field effect mobility increased up to $11.45cm^2{\cdot}V-1{\cdot}s-1$. These all alkali metal doped ZnO TFTs were fabricated at maximum process temperature as low as $300^{\circ}C$. Moreover, low-voltage operating ZnO TFTs was fabricated with the ion gel gate dielectrics. The ultra high capacitance of the ion gel gate dielectrics allowed high on-current operation at low voltage. These devices also showed excellent operational stability.

• 멤브레인
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• 제33권3호
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• pp.87-93
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• 2023

전기투석(ED)은 이온교환막을 통한 이온의 분리에서 중요한 과정이다. 해수담수화로 발생하는 염수 처리는 환경적으로 큰 문제이며 막분리 기술을 통한 재활용 효율이 높다. 마찬가지로 알칼리는 가죽, 전기도금, 염색, 제련 등과 같은 여러 화학 산업에서 생산된다. 폐기물의 고농도 알칼리는 부식성이 높고 화학적 산소 요구량(COD) 값이 높기 때문에 환경에 방출하기 전에 처리해야 합니다. 칼슘과 마그네슘의 농도는 염수의 거의 두 배이며 주요 환경 오염 물질인 이산화탄소의 흡착에 완벽한 후보입니다. 수산화나트륨은 양극성 막 전기투석 공정으로 쉽게 생산되는 금속 탄산화 공정에 필수적입니다. 역삼투압(RO), 나노여과(NF), 초여과(UF), ED 등 다양한 공정을 통해 회수가 가능하다. 본 검토에서는 알칼리 회수를 위한 이온교환막에 의한 ED 공정에 대해 논의한다.

• Bulletin of the Korean Chemical Society
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• 제25권10호
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• pp.1474-1476
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• 2004

A sodium ion- selective electrode based on dibenzopyridino-18-crown-6 as membrane carrier was successfully prepared. The electrode exhibits a Nernstian response for $Na^+$ ions within the concentration range of $1.0\;{\times}\;10^{-4}-1.0\;{\times}\;10^{-1}$ M. The response time of the sensor is 20 s. The sodium ion-selective electrode exhibited comparatively good selectivities with respect to alkali, alkaline earth and some transition metal ions.

• 공업화학
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• 제2권3호
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• pp.270-278
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• 1991

게 껍질로부터 단리한 천연고분자인 chitin을 이용하여 특정금속이온에 대하여 높은 선택성을 갖는 carboxymethyl chitin을 합성하였다. 실험에 사용된 chitin 은 개량한 Hackman 법으로 순수한 상태로 제조하고 이를 여러농도의 수산화나트륨 용액으로 akali chitin을 제조한 후, chitin 단위구조의 C-6 위치($CH_2OH$)를 isoproryl alcohol 중에서 monochloroacetic 로 처리하여 카르복시기를 갖는 유도체를 합성하였다. Kjeldahl 법에 의한 질소함량의 분석 및 원소분석에 의해 최적반응조건과 치환율을 구하였고, 이들 수지의 구조는 적외선흡수스펙트럼으로 확인하였다. 낮은 치환도를 가지며 물에 불용인 carboxymethyl chitin은 알칼리 토금속이온들 중 $Ca^{2+}$ 이온에 대하여 가장 높은 선택적 흡착능을 나타내었으며, 이러한 성질은 $KNO_3$나 $NaNO_3$와 같은 중성염이 존재할 때에도 마찬가지였다. Carboxymethyl chitin에 결합된 $Mg^{2+}$ 이온은 $Ca^{2+}$이온이 있는 곳에서 방출되며, 이러한 $Ca^{2+}$및 $Mg^{2+}$ 이온 혼합계를 이용하였다. 합성된 흡착담체는 $Ca^{2+}$, $Mg^{2+}$, $Sr^{2+}$, $Ba^{2+}$ 등의 금속이온들과의 흡착특성을 검토하였고, 나아가 $Na^+$, $K^+$등 공통양이온 존재하에서 특정금속이온의 선택적 흡착능을 atomic absorption spectrometer로 정량, 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제29권7호
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• pp.1295-1296
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• 2008