Optical Transitions in Single-Wall Boron Nitride Nanotubes

Optical transitions in single-wall boron nitride nanotubes are investigated by means of optical absorption spectroscopy. Three absorption lines are observed. Two of them (at 4.45 and 5.5 eV) result from the quantification involved by the rolling up of the hexagonal boron nitride (h-BN) sheet. The nature of these lines is discussed, and two interpretations are proposed. A comparison with single-wall carbon nanotubes leads one to interpret these lines as transitions between pairs of van Hove singularities in the one-dimensional density of states of boron nitride single-wall nanotubes. But the confinement energy due to the rolling up of the h-BN sheet cannot explain a gap width of the boron nitride nanotubes below the h-BN gap. The low energy line is then attributed to the existence of a Frenkel exciton with a binding energy in the 1 eV range

Cathodic electropolymerization on the surface of carbon nanotubes

This paper reports functionalization of carbon nanotubes (CNTs) via cathodic electropolymerization. Indeed, this technique ensures good control of the grafted polymer (PMAN in our study) on the surface of the substrates (CNTs). The study was done both on single-wall nanotubes (SWNTs) and multi-wall nanotubes (MWNTs) following two distinct approaches: on one hand, the CNTs were dispersed in an organic solution under stirring. This option aims at their functionalization by transient contact with a metallic cathode, but did not give promising results. On the other hand, the CNTs were synthesized (produced) on the surface of an electrode that will be used as cathode in the grafting process. The surface modifications were followed by SEM, XPS, TGA (Thermo Gravimetry Analysis)