PREPARATION OF CARBON CLUSTERS WITH CONTROLLED ELECTRONIC PROPERTIES AND THEIR POTENTIAL USE

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The present research has dealt with preparation of carbon clusters with controlled electronic properties and their potential use. The carbon clusters in the present study include fullerenes and carbon nanotubes. The results were summarized as follows.1. The energies of E_F and E_a of C_<60> become larger as the degree of fluorination increases. This results suggest that the control of electronic structure of C_< 60> are possible by the control the fluorine addit on. Highly fluorinated C_<60>F_X ( x >40 ) has a wide band gap larger than 3 eV, whereas, fluorinated fullerenes C_<60>F_X of lower fluorine content ( x <18 ) will have a narrower band gap suitable for potential electronics.2. Electrochemical fluoride-ion doping of fullerene C_<60> thin films ( 250-450 nm ) was carried out in a fluoride-ion conductive solution, MeCN solution of 1M Et_4NF・4HF. Galvanostatic oxidation yielded C_<60>F_<ca.1-3> where fluorine exists as semi-ionic species in the cavity surrounded by C_<60> molecules … More without forming covalent C-F bonds. Fluoride-ion doped C_<70> thin films C_<70>F_<ca.1-6> were also obtained by galvanostatic oxidation.3. Electrochemical lithium insertion into multiwall carbon nanotubes ( MWNTs ) heat treated at 1000-3000℃, and into chemically modified MWNTs by B-doping and by fluorination has been investigated based on Li/1M-LiClO_4-( EC+DEC )/ MWNTs cells with a three-electrode configuration. Electrochemical lithium insertion behavior has also been investigated for single-walled carbon nanotubes ( SWNTs ) prepared by the arc-discharge method. The optimum effects of heat-treatment on the electrochemical lithium insertion into MWNTs were observed at 1000℃. The reversible capacity of MWNTs fairly increased by B-doping and by fluorination. As for SWNTs, the reversible lithium insertion capacity and the coulomb efficiency were found to be 430 mAh/g and 18 % , respectively at the first cycle, even in the absence of any characteristic X-ray diffraction line of the rope structure. Less