Modulating single-walled carbon nanotube opto-electronic properties by dye confinement
Résumé
Dye encapsulation into host single-walled carbon nanotubes is an elegant way to create hybrid nano-systems with tunable opto-electronic properties. To this aim, different kinds of molecules (either electron donor or acceptor, absorbing either in the blue or the red visible range) are encapsulated into metallic or semiconducting nanotubes displaying different diameters. Up to now, we have mainly studied encapsulated quaterthiophene derivatives (4T), tetracyanoquinodimethane (TCNQ) and phthalocyanine (MPc) molecules. In this work, we discuss the supramolecular organization of dyes inside the nanotube, the optical properties and the charge transfer for some of our hybrid systems. For instance, using Raman spectroscopy, a significant electron transfer is reported with 4T, whose magnitude strongly depends on the nanotube diameter, and on the metallic or semiconducting character. Experiments also suggest a photo-activated electron transfer for small diameter (~9 Å) semiconducting and metallic tubes. Confinement of electron donor (4T) (respectively electron acceptor (TCNQ)) into small diameter tubes leads to a red shift (blue shift) of the optical absorption energy and an increase (decrease) of the photoluminescence intensities, evidenced by the photoluminescence excitation maps.