Initial stage of C60 cation formation in superacids

While superacids are solvents for individualizing carbon nanotubes, the behavior of insulating C60 is different. The final ionization state depends on the superacid used. With chlorosulfonic acid, chlorination is observed while with fuming sulfuric acid, sulfonation has been reported. Both reactions are fast and it is important to characterize the first step to understand the involved reaction mechanisms. Employing Raman spectroscopy and first-principles calculations, we show that C60+ is present with chlorosulfonic acid and surprisingly C602+ ions are predominantly formed during the first seconds after immersion in fuming sulfuric acid.