Development of Method to Separation and Punfication 0f Novel-Fullerene Corn-pound Materials Using Plasma Chromatography

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The endohedral metallofullerene K@C_<60> was successfully formed by the energy and flux control of K^+ and C^-_<60> ions flowing into substrates in experiments of the thin-film formation with a potassiumfullerene (K^+_-C^-_<60>) plasma. Since the K@C_<60> production ratio to C_<60> was at most 30% and usually 5〜10% or less, however, it was difficult to clarify the relation between the plasma effect and encapsulation mecharuism. From the abovementioned viewpoint, the experiments were carried out by a sodiumfullerene (Na^+_-C^-_<60>) plasma, where the diameter of Na^+ is srmaller than that of K^+. The following results were obtained.According to the mass analysis of thin films formed on the substrates, the large massspectrum peak (Na(@)C_<60>) corresponding to the Naendohedral fullereoe is observed. The average intensity ratio of Na(@)C_<60> to C_<60> is turned out to be 30〜50%. Moreover, the Na(@)C_<60> production ratio to C_<60> in a narrow region of the substrate attains to 200% or more.When the substrate bias is chansed, the average spectrumpeak intensity of Na(@)C_<60> is found to give the maximum value at a specific voltage.The composition and structure of the thin film are directly investigated by the highresolution electron microscope (HREM) observation. A lot of C_<60> molecules with dark shadows around the centers are observed over the image of the thin film in the narrow region of the substrate. The round material imaged by the HREM is considered to be C_<60> encapsulating Na inside the cage, because the Na^+ diameter almost corresponds to the dark shadow diameter.It can be said that a large amount of production of the Na-C_<60> compound materials containing Na@C_<60> facilitates the constituent analysis and structure observation for the purpose of clarifying their physical and chemical properties. This work is also important in the sence of establishing the method of forming fullerenebased thin films with new functions.