Controlled filling and external cleaning of multi-wall carbon nanotubes using a wet chemical method

A controlled, material-independent and adaptable cold wet chemical procedure is described. It allows organic and inorganic compounds to be confined inside multi-wall carbon nanotubes. The procedure mainly consists of a lyophilization process to fill multi-wall carbon nanotubes (MWCNTs), and a washing method to clean their outer surface without removing the encapsulated material. The technique was tested by synthesizing US crystals inside the nanotubes. Morphological and structural studies of the CdS crystals demonstrated a complete control of the synthesis process, and the possibility of maximizing the crystal size and the filling efficiency that approached 70% of open-ended nanotubes. (c) 2007 Elsevier Ltd. All rights reserved.