Controlling the incorporation and release of C60 in nanometer-scale hollow spaces inside single-wall carbon nanohorns

We succeeded in large-scale preparation of single-wall carbon nanohorns (SWNH) encapsulating C-60 molecules in a liquid phase at room temperature using a "nano-precipitation" method, that is, complete evaporation of the toluene from a C-60-SWNH-toluene mixture. The C-60 molecules were found to occupy 6-36% of the hollow space inside the SWNH, depending on the initial quantity of C-60, We showed that the C-60 in C-60@SWNHox was quickly released in toluene, and the release rate decreased by adding ethanol to toluene. Numerical analysis of the release profiles indicated that there were fast and slow release processes. We consider that the incorporation quantity and the release rate of C-60 were controllable in/from SWNHs because SWNHs have large diameters, 2-5 nm.