Involved researchers : F. Dragin (PhD), E. Anglaret
Collaboration : A. Pénicaud (CNRS Bordeaux) and R. Martel (Dpt Chemistry, U. Montréal
Nanotubes salts (charge transfer systems nanotube-alkali atoms) are soluble in polar aprotic solvents and form polyelectrolyte solutions. We studied the structure and optical properties of nanotubes in polyelectrolyte solutions. Coupled AFM and X-ray diffraction studies demonstrated that the nanotubes are essentially individual in the solutions. We showed that redox titration could be used to control the global density of charges in the solutions. The Raman signatures of the nanotubes change continuously during the titration and the results indicate a direct charge-transfer reaction from the acceptor molecules to the nanotubes, leading to their gradual neutralization.
We also studied charge transfer in an electrochemical cell. We found that charge transfer can be achieved selectively on different (n,m) nanotubes because of their different electronic structures. We used Raman spectroscopy to study selective (n,m) undoping and p-doping as a function of electrochemical potential (see figure). We found that the potentials for undoping and doping nanotubes depend on the diameter and chiral angle. These measurements allowed us to measure the work function of individual (n,m) nanotubes
A. Pénicaud et al, JACS 127(1), 8 (2005) ; A. Pénicaud et al, Comp. Science and Tech. 67, 795 (2007)
E. Anglaret et al., J. Phys. Chem. B 110, 3949 (2006)
Funding : ANR P-NANO TRICOTRA, CRSNG-Canada and Lavoisier-France grants