title: Selective probe of the morphology and local vibrations at carbon nanoasperities.
abstract: We introduce a way to selectively probe local vibration modes at nanostructured asperities such as tips of carbon nanohorns. Our observations benefit from signal amplification in surface-enhanced Raman scattering (SERS) at sites near a silver surface. We observe nanohorn tip vibration modes in the range 200-500 cm(-1), which are obscured in regular Raman spectra. Ab initio density functional calculations assign modes in this frequency range to local vibrations at the nanohorn cap resembling the radial breathing mode of fullerenes. Careful interpretation of our SERS spectra indicates presence of caps with 5 or 6 pentagons, which are chemically the most active sites. Changes in the peak intensities and frequencies with time indicate that exposure to laser irradiation may cause structural rearrangements at the cap.
authors.affiliation: Research Center for Exotic Nanocarbons (JST), Shinshu University, 4-17-1, Wakasato, Nagano-city 380-8553, Japan.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Fujimori
authors.forename: Koki
authors.initials: K
authors.lastname: Urita
authors.forename: David
authors.initials: D
authors.lastname: Tománek
authors.forename: Tomonori
authors.initials: T
authors.lastname: Ohba
authors.forename: Isamu
authors.initials: I
authors.lastname: Moriguchi
authors.forename: Morinobu
authors.initials: M
authors.lastname: Endo
authors.forename: Katsumi
authors.initials: K
authors.lastname: Kaneko