Probing the Interior Environment of Carbon Nano-test-tubes
  We report the filling of single walled carbon nanotubes with an electron spin-active fullerene species where a nitroxide radical is functionalized on the fullerene cage. High resolution transmission electron microscopy (HRTEM), optical absorption and electron spin resonance (ESR) are used to determine the rotational behavior of the encapsulated molecules and determine the polar nature of the nanotube interior. 
Andrew A. R. Watt, Mark R. Sambrook, Stanislav V. Burlakov, Kyriakos   Porfyrakis, G. Andrew D. Briggs