Non-linear and resonance effects in carbon nanotube structures

• Published in: Optical materials Vol. 33; no. 9; pp. 1410 - 1414
• Main Authors: Lefrant, S., Buisson, J.P., Mevellec, J.Y., Baibarac, M., Baltog, I.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-07-2011; Elsevier
• Subjects: Amplification; Carbon nanotube/conjugated polymer composites; Carbon nanotubes; Coherent Anti-Stokes Raman Scattering; Coherent scattering; Condensed Matter; Materials Science; Physics; Polymer matrix composites; Polymerization; Polymers; Raman scattering; Single wall carbon nanotubes; Surface Enhanced Raman Scattering; Carbon nanotubes; Raman scattering; Surface Enhanced Raman Scattering; Carbon nanotube/conjugated polymer composites; Coherent Anti-Stokes Raman Scattering
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/j.optmat.2011.03.014

► Anomalies of the anti-Stokes Raman intensities are observed in carbon nanotubes. ► A single beam CARS (Coherent Anti-Stokes Raman Scattering) mechanism is evidenced. ► The role of resonant conditions is investigated for the low frequency Raman modes. ► Metallic tubes are expected to induce an anti-Stokes amplication in nanocomposites.
In this paper, we report on Raman scattering and Surface Enhanced Raman Scattering (SERS) studies of single walled carbon nanotubes (SWNTs) and carbon nanotube/conjugated polymers composites. We demonstrate that under SERS conditions we induce an abnormal anti-Stokes Raman emission, that can be interpreted as being due to a “single-beam pumped” Coherent Anti-Stokes Raman Scattering (CARS) effect. We also investigate in detail the anti-Stokes/Stokes (aS/S) intensity ratios of the radial breathing modes (RBMs) of SWNTs as a function of several parameters. From calculations, we show that resonance phenomena mostly explain the aS/S intensity ratio anomalies, but only at low frequencies. In addition, we describe results obtained with polymers like poly(bithiophene) (PBTh) polymerized on carbon nanotube thin films which exhibit also an amplification of its high frequency Raman modes in the anti-Stokes branch, generated by the plasmon excitation of metallic tubes. This phenomenon occurs in several other materials such as composites based on SWNTs and conjugated polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT) and polyparaphenylene-vinylene (PPV) for modes located around 1500
cm
−1.