The effect of salt concentration on the optical modes of charged cylindrical nanotubes

Abstract

Articles you may be interested inSimple model of bulk and surface excitation effects to inelastic scattering in low-energy electron beam irradiation of multi-walled carbon nanotubes Study of geometrical effects on the characteristics of metallic double-walled carbon nanotube waveguides through quantum hydrodynamics Phys. Plasmas 16, 063501 (2009); 10.1063/1.3142468 Carrier density and quantum capacitance for semiconducting carbon nanotubesWe have conducted calculations of the collective plasmon excitations for an electron gas confined to the surface of a charged single-walled cylindrical nanotube in salt solutions. Both positively and negatively charged nanotubes are investigated. At high salt concentration, the surface potential approaches zero, and the spectrum is close to that of a neutral nanotube. The highest-frequency branch of the plasmon excitation spectrum exhibits a redshift and a blueshift for negatively and positively charged nanotubes, respectively. Such a result can be attributed to the change of the number of eigenstates around the Fermi energy. As salt concentration is increased, the surface potential is screened out, and the spectral line shift diminishes. Our results also show that the negatively charged nanotube can be more sensitive to the ambient salt concentration than the positively charged one. The optimal sensor device occurs when the nanotube carries a linear charge density close to that of DNA. The theoretical predictions suggest that charged nanotubes have the potential as sensors to probe salt concentration.

Raman and FTIR spectroscopy as valuable tools for the characterization of polymer and carbon nanotube based composites

“…17 stretching mode in the quinoid structure of thiophene rings, respectively. [69][70][71] As shown in Fig. 17, curve b, subsequent treatment with a 1 M NH 4 OH solution of the oxidized PBTh film induces modifications in the Raman spectrum: i) a strong decrease in intensity, almost until disappearance, of the Raman lines peaking at 644-735, 1158, 1221 and 1356 cm À1 ; ii) a down-shift of the Raman lines situated in the spectral domain of 1000-1100 cm À1 ; iii) the appearance of a complex band with two distinct maxima at 1439 and 1460 cm À1 which are attributed to symmetric stretching modes of the C]C bond of quinoid and aromatic rings, respectively; iv) a weaker band, like a shoulder at 1502 cm À1 , attributed to the anti-symmetric stretching mode of the C]C bond.…”