Influence of nitrogen on carbon arc plasma and formation of fullerenes

The influence of nitrogen on the process of fullerene formation in the carbon arc discharge in a helium/nitrogen atmosphere has been studied. Applying optical emission spectroscopy and using the self-absorption effect, the spatial distribution of the temperatures and chemical species, i.e. C2(a3Πu, v″=0) and CN(X2Σ+, v″=0) radicals produced by the d.c. arc discharge between pure graphite electrodes, were determined across the arc gap. The soot product was analyzed spectrophotometrically to determine C60 content. C60 was detected even when pure nitrogen was used (at about 0.5 wt%). The relative content of higher fullerenes was measured by mass spectrometry and their formation was found to be significantly enhanced in the presence of nitrogen.