Influence of oxygen on the production of higher fullerenes

In an attempt to increase the production yield of the higher fullerenes (C-76, C-78, C-84, etc.), Hf-, Zr- and Ti-doped electrodes were used in an are discharge process along with undoped electrodes for comparison. The soot was analysed by high-performance liquid chromatography. We found the following relations: (i) The yield of higher fullerenes is anticorrelated with the yield of C60O and (ii) Hf, Zr and Ti doping reduces the C60O yield and accordingly increases the yield of higher fullerenes. We suggest that the primary effect of the dopants is a reduction of the oxygen partial pressure by the getter action of the coevaporated materials and, as a result, the higher fullerenes are formed more abundantly.