Absorption coefficient and electron affinity of a water-soluble single-walled carbon nanotube

The luminescence from excited Ru(bpy)32+ was analyzed in aqueous solutions containing a water-soluble single-walled carbon nanotube. The amount of sulfonic groups on the carbon nanotubes was derived by a detailed comparison of the luminescence intensity, and it was shown that the value of the absorption coefficient of these carbon nanotubes is ca. 2.6×104 L/(gram atom·cm). The quenching of Ru(bpy)32+ luminescence by the carbon nanotubes is also discussed and its mechanism is shown to be an electron-transfer to the carbon nanotube.