Tailoring the Properties of Single-Wall Carbon Nanotube Samples through Structure-Selective Near-Infrared Photochemistry.

Abstract

As-produced samples of single-wall carbon nanotubes (SWCNTs) contain many structural forms with characteristic properties. In particular, semiconducting SWCNTs display distinct near-IR optical absorption and emission peaks. We show that the selective irradiation of these absorption features can induce structure-specific functionalization in unsorted SWCNT samples. This approach is demonstrated with an ambient temperature photoreaction involving dissolved O2 and irradiation at 955, 985, and 1130 nm, causing preferential covalent reactions of (8,3), (6,5), and (7,6) SWCNTs, respectively. Treated samples showed permanent fluorescence quenching and absorption bleaching near the irradiation wavelength and an increase in the Raman D/G intensity ratio, indicating the formation of covalent defects. The reaction has a very low photochemical quantum yield and was observed for samples suspended in single-stranded DNA and in conventional surfactants that gave incomplete coverage of the nanotube surface. The approach of exploiting sharp nanotube near-IR transitions for structure-selective photochemistry provides a path to tailor SWCNT optical properties for several potential applications without the need for physical sorting.