Extraordinary sensitivity of the electronic structure and properties of   single-walled carbon nanotubes to molecular charge-transfer
  Interaction of single-walled carbon nanotubes with electron donor and acceptor molecules causes significant changes in the electronic and Raman spectra, the relative proportion of the metallic species increasing on electron donation through molecular charge transfer, as also verified by electrical resistivity measurements. 
Rakesh Voggu, Chandra Sekhar Rout, Aaron D. Franklin, Timothy S.   Fisher and C. N. R. Rao