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  • 02월 23일 15시 이후 : 초록수정 불가능, 일정확인 및 검색만 가능

New Insight into TiO32- Quantum Wires in ETS-10: Effects of Electron Density

2009년 2월 17일 15시 02분 13초
37P284포 이곳을 클릭하시면 발표코드에 대한 설명을 보실 수 있습니다.
목 <발표Ⅱ>
저자 및
정낙천, 윤경병
서강대학교 화학과, Korea
Efforts have been focused at 1-dimensional quantum wire (QW) to be used as building blocks for nanoscale electronic devices. However, their physical properties have not been elucidated due to the lack of the method of synthesizing them in uniform diameter. ETS-10, a type of zeolite, carries a superlattice of 0.67-nm-thick TiO32- QWs imbedded in a nanoporous silica matrix from birth. TiO32- QWs in ETS-10 has been regarded as an ideal example since their thickness is very uniform. But their physical properties have also not been elucidated due to inability of synthesizing ETS-10 crystals with high quality. Eventually, we successfully synthesized high-crystalline ETS-10 crystals and revealed their physical properties such as vibrational frequency and bandwidth on Raman, chemical shifts on 29Si NMR, and bandgap on absorption spectra. Those are changed upon varying the electron density on QWs. The electron density on the QW was varied by varying the type of cations within the zeolite framework and the water contents in ETS-10. As electron density increases, vibrational frequency shifts to a higher energy region and bandwidth decreased, akin to the property of metallic SWNT. Three 29Si NMR peaks also shift to the down-field as electron density increases. From the different sensitivity of the chemical shifts, each type of Si atom was assigned in ETS-10 structure. It was also demonstrated for the first time that the bandgap can be controlled by changing electron density. Changes in bandgap were more sensitive in dehydrated than hydrated condition since water molecules obstruct the interaction between cations and QWs.