Reacting soluble single-walled carbon nanotubes with singlet oxygen

Soluble single-walled carbon nanotubes were oxidized with singlet oxygen (1Δg) and the reaction progress was monitored utilizing FT-IR and UV–vis–NIR spectroscopy. The results indicate reversible covalent addition of oxygen to the walls of the nanotubes, most likely producing either the [2 + 2] or [4 + 2] cycloaddition product. Oxidative selectivity of singlet oxygen for metallic over semiconducting SWNTs was demonstrated and it is proposed that this selectivity can be utilized as a method for nanotube purification.