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|Model of C60 fullerene - At which vertex or on which side of the pentagon and hexagon will two molecules be combined?|
Elucidation of a chemical reaction of fullerene molecules by high-resolution electron microscopy
* Fullerene molecules were visualized at the atomic level by confining the molecules in carbon nanotubes, applying a low acceleration voltage, and using an aberration correction system and mathematical image processing.
* The chemical reaction of the molecules was controlled by changing conditions such as molecular orientations and concentrations, temperatures, presence or absence of metal atoms, and applied energy used in the chemical reactions.
* The visualizing technique is expected to have a wide variety of applications such as elucidation of reaction mechanisms, dynamic analysis of molecular interactions, and molecular design.
Masanori Koshino (Research Scientist), the Nano-carbon Characterization Team (Leader: Kazutomo Suenaga) and Toshiya Okazaki (Senior Research Scientist) of the Nanotube Research Center (Director: Sumio Iijima), Hiromichi Kataura (Leader), the Self-Assembled Nano-Electronics Group of the Nanotechnology Research Institute, the National Institute of Advanced Industrial Science and Technology (AIST) (President: Tamotsu Nomakuchi), Yoshiko Niimi (Research Technical Assistant), the Japan Science and Technology Agency (JST), and Eiichi Nakamura (Professor), the Department of Chemistry, Graduate School of Science, the University of Tokyo, have jointly succeeded in the atomic level analysis of the reactivity and selectivity of the dimerization reaction of fullerene molecules.
In this study, the group confined the fullerene molecules in single-walled carbon nanotubes and optimized the chemical reactivity of the molecules by changing parameters such as concentration, temperature, effects of metal atoms and energy imparted, thereby visualizing the chemical reaction of the molecules under a high-resolution electron microscope with an aberration correction system. The visualization revealed that the orientation of each molecule directly affected the reaction. It is expected that this technique has a wide variety of applications including elucidation of various reaction mechanisms and molecular design, e.g., in the development of new drugs.
The results were obtained from the ERATO research project titled "Nakamura Active Carbon Cluster Project" (Research General Manager: Eiichi Nakamura) and the research theme "Development of low-acceleration and high-sensitivity electron microscope enabling observation of soft matters at molecular and atomic levels" (Research representative: Kazutomo Suenaga) in the CREST research field titled "New measurement and analysis base technique contributing to elucidation and application of material phenomena" (Research General Manager: Michiyoshi Tanaka, Emeritus Professor, Tohoku University); the projects were implemented under the Basic Research Programs of JST. The details of the research will be published in an online edition of a British scientific journal, Nature Chemistry at 3 am, January 11, 2010 (Japan standard time).
Social Background for Research
Chemical reactions range from familiar reactions that are indispensable for life activities such as respiration and digestion to those are essential for modern industry, such as chemical syntheses and energy conversion. The reactive part of a molecule can be predicted theoretically to some extent, but this prediction is very difficult in some actual chemical reactions. One example is the fusion of fullerene molecules in which different chemical reactions occur simultaneously and various products are obtained. Since conventional chemical analyses were based on the statistics to analyze the average behavior of large numbers of molecules, they were not effective for examining the reactions that produce mixed various products. On the contrary, it is believed that the new technique of nanotechnology enables us to analyze the behaviors of individual molecules and to clarify their reactions. Atomic information during the course of chemical reactions is expected to elucidate several unknown phenomena. This is the reason why such new analyses of nanotechnology have been demanded and developed.
History of Research
Organic molecules are composed of light elements. It was very difficult to observe the behavior of such light molecules at the atomic level. In recent years, however, it has become possible to observe the behavior of one small organic molecule by confining it in a carbon nanotube with nanometer-sized internal space. It has been proved that this confinement technique can be applied to the analyses of molecular behaviors. One of the next goals is to visualize each molecule involved in a chemical reaction at the atomic level. The visualization is expected to provide knowledge that has not been acquired by using other analysis methods, to contribute to the understanding of chemical reactions at the atomic level, and to elucidate reaction mechanisms.
The group has succeeded in observing the reaction processes of fullerene molecules confined in carbon nanotubes at the atomic level by using an electron microscope with a low acceleration voltage and an aberration correction system, in combination with fast-Fourier-transform image processing. The development of the electron microscopy enabled high-resolution observations under various environments such as ultra low temperatures (-269 °C) and low acceleration voltages (80 kV). The results indicate that molecular behaviors and chemical reactions could be controlled.
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