Polarization effects in surface-enhanced resonant Raman scattering of single-wall carbon nanotubes on colloidal silver clusters (original) (raw)
Related papers
Physical Review B, 2005
We present experimental evidence of drastic changes in low-frequency Raman scattering spectra depending on the polarization of the incident laser with respect to the single-walled carbon nanotube ͑SWNT͒ axis. Employing recently developed vertically aligned SWNT films, which have a high density ͑1.0ϫ 10 17 m −2 ͒ and a thickness of 5 m, enabled us to obtain sufficient Raman scattering intensity from the film cross section where bundles of SWNTs are aligned along the same direction, in addition to from the top surface of the film. The measured peaks of the radial breathing mode ͑RBM͒ by 1.96, 2.41, and 2.54 eV incident lasers are clearly distinguished into 2 groups. One group of peaks is dominant for perpendicular polarization while the other group of peaks is dominant in the case of light polarized parallel to the SWNT axis. The selective vanishing of the perpendicular peaks by adsorption of molecules to the SWNTs along with the resultant change in optical absorption spectrum evidences that the parallel and perpendicular peaks originate from ⌬ = 0 and ⌬ = ±1 excitations of electrons, respectively. The grouping behavior of RBM peaks also causes the drastic spectral variation caused by a change in incident laser power. The unambiguous classification of each RBM peak's nature presented in this study will allow sounder characterization of SWNTs by the resonant Raman scattering analysis.
Physical Review B, 2002
We studied the polarization dependence of the resonance Raman spectra for several different isolated singlewall carbon nanotubes ͑SWNTs͒. One isolated SWNT acts as a dipolar antenna, polarized along the tube axis. For light polarized parallel to the tube axis, the strong resonance-effect breaks the symmetry-selection rules, and symmetry-forbidden modes appear in the Raman spectrum. When the light is not polarized parallel to the tube axis, G-band mode symmetries can be identified. Unusual G-mode intensity behavior is observed when the Raman signal is obtained from more than one SWNT, suggesting a complex multipolar antenna pattern.
Amplification of a Raman Scattering Signal by Carbon Nanotubes
Doklady Physics, 2018
The effect of Raman scattering (RLS) signal amplification by carbon nanotubes (CNTs) was studied. Single-layered nanotubes were synthesized by the chemical vapor deposition (CVD) method using methane as a carbon-containing gas. The object of study used was water, the Raman spectrum of which is rather well known. Amplification of the Raman scattering signal by several hundred percent was attained in our work. The maximum amplification of a Raman scattering signal was shown to be achieved at an optimal density of nanotubes on a substrate. This effect was due to the scattering and screening of plasmons excited in CNTs by neighboring nanotubes. The amplification mechanism and the possibilities of optimization for this effect were discussed on the basis of the theory of plasmon resonance in carbon nanotubes.
Resonant Raman Scattering in Carbon Nanotubes
physica status solidi (b), 2000
We present resonant-Raman scattering results on single and multi-walled carbon nanotubes in the range 1.5 to 2.6 eV. In addition to the known resonance of metallic tubes with a maximum at % 1:9 eV we determine the resonance profile of semiconducting single-walled tubes. For a diameter of d 0 1.3 nm it has a flat minimum between 1.8 and 2.3 eV and a resonance above and below that. For tubes with d 0 1:45 A all resonance energies decrease by about 0.1 eV. For multi-walled tubes a monotonic increase in Raman intensity with excitation energy is observed which is explained as a smearing out of the square-root singularities in the electronic density of states of 1D systems.
Raman scattering of linear chains of strongly coupled Ag nanoparticles on SWCNTs
Scientific Reports, 2014
We compare the Raman scattering properties of hybrid nanostructures consisting of Ag nanoparticles (NPs) in disordered and aligned arrangements on single-walled carbon nanotubes (SWCNTs) as a result of chemical and photoreduction methods. In the latter case, the unique structure of the very small Ag NP (from 4 to 7 nm) chains generated an extremely large mode at 969 cm 21 that was assigned to the sulphate-silver interaction at the NP surface. Another strong mode was present at 1201 cm 21 and was assigned to an IR-active mode of sodium dodecyl sulphate (SDS); this mode was observed because the symmetry changes altered the selection rules. We demonstrate that both the UV photoreduction of silver and the presence of SWCNTs are necessary to produce this very strong Raman scattering. The Raman modes of the SWCNTs are also significantly modified by the presence of Ag NP chains along the nanotubes.
2012
Surface enhanced resonance Raman scattering (SERRS) has been applied to investigate defects in purified and carboxylated single-walled carbon nanotubes (SWCNTs). For both samples SERRS spectra with temporal fluctuating peak intensities and positions in the range of 1000–1350cm− 1 have been observed. A series of peaks in this window coincide with peak positions that have been assigned to arise from Stone–Thrower–Wales and heptagonal–pentagonal intramolecular junction defects on the nanotubes surface.
Resonance Raman Spectra of Carbon Nanotubes by Cross-Polarized Light
Physical Review Letters, 2003
Resonance Raman studies on single wall carbon nanotubes (SWNTs) show that resonance with cross polarized light, i.e., with the E ;1 van Hove singularities in the joint density of states needs to be taken into account when analyzing the Raman and optical absorption spectra from isolated SWNTs. This study is performed by analyzing the polarization, laser energy, and diameter dependence of two Raman features, the tangential modes (G band) and a second-order mode (G 0 band), at the isolated SWNT level.
Characterizing carbon nanotube samples with resonance Raman scattering
New Journal of Physics, 2003
The basic concepts and characteristics of Raman spectra from carbon nanotubes (both isolated and bundled) are presented. The general characteristics of the radial breathing mode, tangential mode (G band), disorder-induced mode (D-band) and other Raman features are presented, with the focus directed toward their use for carbon nanotube characterization. Polarization analysis, surface enhanced Raman spectroscopy and complementary optical techniques are also discussed in terms of their advantages and limitations.