Interactions of Gold Nanoparticles with the Interior of Hollow Graphitized Carbon Nanofibers

Interactions of free-standing gold nanoparticles and hollow graphitized nanofibers in colloidal suspension are investigated, revealing the first example of the controlled arrangement of nanoparticles inside nano-containers, as directed by their internal structure. The ordering is highly effective for small gold nanoparticles whose sizes are commensurate with the height of graphitic step-edges in the graphitized carbon nanofibers and is less effective for larger gold nanoparticles. Studies aimed at understanding the role of the organic-solvent surface tension, employed for the filling experiments, demonstrate that gold nanoparticles become preferentially anchored into the hollow graphitized carbon nanofibers under a mixture of pentane/CO2 in supercritical conditions. It is shown that a three-step cleaning procedure enables effective removal of gold nanoparticles adsorbed on the exterior surface of graphitized carbon nanofibers, while ordered arrays of encapsulated nanoparticles are retained.