Optical properties of carbon nanotubes in a composite material: The role of dielectric screening and thermal expansion

Abstract

We report on environmental effects on the optical properties of single-wall carbon nanotubes in a gelatin-based composite material designed to foster their photoluminescence. We show that the dielectric screening of excitons due to the surrounding medium is responsible for a sizeable shift of the luminescence lines which hardly depends on the tube geometry. In contrast, the temperature dependence (from 4 to 300 K) of the luminescence is clearly chirality dependent : the first and second excitonic lines shift in opposite directions with a magnitude that can be related quantitatively to a strain-induced modification of the electronic structure due to an expansivity mismatch between the nanotube and the matrix.PACS numbers:

Π‐Stacking Functionalization of Carbon Nanotubes through Micelle Swelling

“…Therefore, we conclude that this effect arises from a dielectric screening of excitons and not from a strain-induced band-shift (as observed for some surfactants [22,23] ) that would result in opposite shifts for S 22 and S 11 lines. [24] Remarkably, the amplitudes of PLE lines corresponding to porphyrin Soret band and to S 22 nanotubes transitions are of the same order of magnitude. This means that the number of photons emitted by the SWNTs is the same when the SWNTs are excited directly (S 22 absorption) or through TPP absorption.…”

Quantum efficiency of energy transfer in noncovalent carbon nanotube/porphyrin compounds

“…The spot corresponding to (6,5) nanotubes is red-shifted both in excitation and emission energies. This shift results from a dielectric screening of the excitonic transition by the porphyrin molecules [10]. Compared to the PLE map of nanotubes, additional spots are visible along the vertical dashed line for excitation energies of 2.805 and 2.357 eV.…”

Controlling carbon nanotube photoluminescence using silicon microring resonators

“…PL was also observed in an ensemble of s-SWNT [5], and more recently in compositelike materials where nanotubes are dispersed into a gelatin [6] or a polymer matrix [7,8], opening the route towards device fabrication. Furthermore, it is possible to stretch and align nanotubes dispersed in the matrix to enhance their PL properties [7,9].…”