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중성 수용액에서 폴리피롤의 전기화학적 성장시 발생하는 점탄성 변화에 미치는 음이온 효과
배상은,이승용,백세환,김영상,이치우,Bae Sang-Eun,Lee Seung-Yong,Paek Se-Hwan,Kim Young-Sang,Lee Chi-Woo 한국전기화학회 1999 한국전기화학회지 Vol.2 No.2
수용액에서뿐만 아니라 유기용매에서도 폴리피롤이 전기화학적으로 전극표면에서 잘 성장한다는 많은 연구가 보고되어 있다. 근래에 들어서 폴리피롤을 산업적으로 사용하려는 노력이 많지만 기본적인 물리적 그리고 화학적 성질은 알려지지 않은 것이 많다. 특히, 폴리피롤의 미세유변학적 성질은 전기화학적 수정결정 진동자법이 알려지기 이전까지 거의 무시되어 왔다. 본 논문에서는 중성 수용액에서 폴리피롤을 전기화학적으로 성장시킬 때 발생하는 폴리피롤의 점탄성도 변화를 전기화학적 수정결정 진동자법으로 조사하였다 그 결과 $KPF_6$ 와 $KCIO_4$중성 수용액에서 합성된 막이 $KCI,\;KNO_3,\;KBr,\;KBF_4,\;K_2SO_4$, sodium tosylate(NaOTs), sodium dodecyl sulfate (SDS) 각각의 중성 수용액에서 합성된 막보다 점탄성도가 더 크며 폴리피롤의 전극 표면에서의 성장 속도가 SDS중성 수용액에서 가장 빠르다는 것을 발견하였다. 또한 중성 수용액에서 합성한 폴리피롤이 비완충 수용액에서 합성한 막보다 탄성도가 더 컸다 A large number of works have been Performed to understand the electrochemical growth of Polypynole on conducting substrates in aqueous as well as in nonaqueous solutions. Recently most researches with Polypyrrole have tended to be directed toward technological applications, but many fundamental physical and chemical properties of Polypyrrole remain unknown. In Particular, microrheological Property of polypyrrole has been largely neglected until the advanced electrochemical quartz crystal microbalance technique was introduced recently. To study anion effects on microrheolosical Property of Polypyrrole, we investigated changes in viscoelasticity of Polypyrrole during electrochemical growth in neutral aqueous solutions by means of in siか electrochemical quartz crystal oscillator method. The results showed that the films of Polypyrrole synthesized in $KPF_6\;and\;KCIO_4$ were more viscoelastic than the ones in $KCI,\;KNO_3,\;KBr,\;KBF_4,\;K_2SO_4$, sodium tosylate (NaOTs), and sodium dodecyl sulfate (SDS). The growth rate of Polypyrrole in SDS was faster than that in the others utilized. Polypyrroles synthesized in buffered neutral solutions were more elastic than those in unbuffered neutral solutions.
배상은,Mi-Kyung Oh,민남기,백세환,홍석인,이치우 대한화학회 2004 Bulletin of the Korean Chemical Society Vol.25 No.12
Electrochemical, in situ electrochemical scanning tunneling microscope (EC-STM), and attenuated total reflectance-FTIR (ATR-FTIR) spectroscopic methods were employed to investigate the preparation of atomically flat Si(111)-H surface in ammonium fluoride solutions. Electrochemical properties of atomically flat Si(111)-H surface were characterized by anodic oxidation and cathodic hydrogen evolution with the open circuit potential (OCP) of ca. −0.4 V in concentrated ammonium fluoride solutions. As soon as the natural oxide-covered Si(111) electrode was immersed in fluoride solutions, OCP quickly shifted to near −1 V, which was more negative than the flat band potential of silicon surface, indicating that the surface silicon oxide had to be dissolved into the solution. OCP changed to become less negative as the oxide layer was being removed from the silicon surface. In situ EC-STM data showed that the surface was changed from the initial oxidecovered silicon to atomically rough hydrogen-terminated surface and then to atomically flat hydrogenterminated surface as the OCP moved toward less negative potentials. The atomically flat Si(111)-H structure was confirmed by in situ EC-STM and ATR-FTIR data. The dependence of atomically flat Si(111)-H terrace on mis-cut angle was investigated by STM, and the results agreed with those anticipated by calculation. Further, the stability of Si(111)-H was checked by STM in ambient laboratory conditions.
Si(111)-H 표면의 전기화학적 제조에 관한 전기화학적 주사터널링현미경법 연구
배상은,이치우,Bae, Sang-Eun,Lee, Chi-Woo 한국전기화학회 2002 한국전기화학회지 Vol.5 No.3
Electrochemical scanning tunneling microscopy was employed to study the evolution of surface morphology during electrochemical preparation of Si(111)-H from Si(111) oxide. Anodic dark current of cyclic voltammogram in 0.2M $NH_4F$ solution (pH 4.7) decreased as the number of cycles increased and remained nearly constant after the second cycle. Then, the Si(111) oxide was entirely stripped, which was followed by H termination on the Si(111) surface. Hydrides at kink and step sites were etched more rapidly than on the terrace, which remained triangle pits with [112] oriented steps where existed stable monohydride. Then, triangle pits deepened. During chronomamperometry at 0.4V anodic dark current shoulder appeared and decreased slowly, indicated the stripping of Si(111) oxide and the formation of stable (112) oriented steps with monohydride. Additionally, the etching mechanism of Si(111)-H in 0.2M $NH_4F(pH 4.7)$ solution at +0.4V was discussed. 묽은 불산용액에서 Si(111) 산화막 (SiOx) 표면을 전기화학적으로 에칭할 때 생성되는 Si(111)-H 표면변화를 전기화학적 주사터널링현미경을 사용하여 조사하였다. pH가 4.7인 0.2M $NH_4F$ 용액에서 순환전압전류곡선은 순환 횟수가 증가할수록 양극 암전류가 감소하였고 두 번 이상 순환한 시료의 암전류는 일정한 형태의 전압전류곡선을 나타냈다. 이때 표면은 모든 SiOx층이 벗겨져 수소말단화된 구조를 가졌으며, 그 이후 순환에서는 생성된 Si(111)-H 표면의 이중 수소결합이 없어지는 step-flow반응이 일어나, 표면이 단일수소결합을 가지는 [112]모서리의 안정한 삼각형 모양을 나타냈으며 또한 생성된 삼각형 흠의 깊이가 점차 깊어졌다. 일정전압법에서는 초기에 큰 양극 암전류 최고 값을 나타낸 후, 시간에 따라 양극 암전류가 감소하였다. 양극 암전류 최고 값 후. 표면의 모든 SiOx가 벗겨졌으며 이후 양극 암전류는 작은 값을 띠면 조금씩 더 낮아졌다. 이 낮아지는 양극 암전류 역시 이중수소 결합의 step-How반응에 안정한 단일수소결합의 [112]모서리 생성에 의해 나타난다. pH 4.7인 0.2M $NH_4F$용액중의 Si(111)-H표면에 +0.4V를 가할 때 진행되는 에칭반응의 메커니즘에 관해서 논하였다.