We study the effects of adding H 2O 2 to acid-purified and unpurified single-walled carbon nanotubes (SWNTs) in aqueous suspensions using photoluminescence (PL) and optical absorption spectroscopies. The addition of H 2O 2 to suspensions of unpurified SWNTs results in a rapid (1-2 h) quenching of the photoluminescence from all tubes, whereas H 2O 2 addition to acid-purified SWNTs causes the nanotube PL to grow in intensity over a period of several days before decaying in a tube-specific manner that depends on the binding strength of the surfactant sheath. With the appropriate choice of surfactants, the PL for specific acid-purified SWNTs can be protected such that novel mid-gap and phonon-assisted absorption and emission transitions can be observed without the obscuring effects associated with emission from other nanotubes. The H 2O 2 treatment also results in a reduction of the high-energy absorption background that has been associated with either carbonaceous impurities or the SWNT π-plasmon oscillation. An understanding of the related mechanisms leads to a new method for separating nanotubes by type based on selective oxidation followed by selective precipitation. These findings offer the possibility of efficiently separating large quantities of nanotubes by chirality.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films