HWAHAK KONGHAK, Vol.35, No.3, 407-411, June, 1997
그래파이트 표면에 증착된 자기결합 헤테로폴리산 단분자층의 STM 연구: NDR 거동과 산화환원 반응성
Scanning Tunneling Microscopy of Self-Assembled Heteropolyacid Monolayers Deposited on Graphite Surface: NDR(Negative Differential Resistance) Behavior and Redox Activity
초록
본 연구에서는 STM(scanning tunneling microscopy)에 의해 측정된 헤테로폴리산의 NDR(negative differenrial resistance) 거동과 헤테로폴리산의 산화환원력과의 상관관계에 대하여 살펴보았다. 이를 위해 양이온 및 배위원소가 헤테로폴리산의 NDR 거동에 미치는 영향을 조사하였다. 헤테로폴리산의 NDR 거동은 촉매의 전자적인 성질, 즉 촉매의 산화환원능력과 밀접한 관련이 있는 것으로 나타났다. 산화환원능력이 우수한 헤테로폴리산일수록 낮은 음전압에서 NDR 거동이 나타났다. 또한 헤테로폴리산의 환원상태에 따른 산소이탈량은 NDR 전압 변화량과 밀접한 관련이 있는 것으로 나타났다. 따라서 STM에 의해 측정된 헤테로폴리산의 NDR 거동은 촉매의 산화환원능력을 예측하는 지표가 될 수 있음을 알 수 있었다.
A correlation between redox potential and NDR(negative differential resistance) behavior of heteropolyacid probed by STM(scanning tunneling microscopy) was examined in this work. The effects of counter cations and polyatoms on the NDR behavior of heteropolyacid were examined for this purpose. It was revealed that NDR behavior was closely related to the electronic property of heteropolyacid, and in turn to the redox potential of heteropolyacid. More reducible heteropolyacid showed NDR behavior at less negative voltage. It was also found that the amounts of oxygen loss from polyanion with respect to reduction state was related to the changes in NDR voltage. It was concluded that NDR behavior of heteropolyacid probed by STM could be a fingerprint for the prediction of redox potential of heteropolyacid.
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