Authors: R. Clarke
Affilation: Thomas Swan & Company Limited, United Kingdom
Pages: 8 - 11
Keywords: carbon nanotubes, steam purification, filling, functionalisation
A substantial body of research has been focused on the preparation of high purity carbon nanotubes (CNT) in a large scale. Subsequently the purified CNTs can then be filled or functionalized depending on the envisaged application. Typically amorphous carbon, graphitic particles and metal particles are the main impurities in as-made CNTs. Although several procedures have been used to remove them off, the nitric acid has become the standard reagent for purification of CNTs and constitutes one of the key steps in many different purification schemes. Recent studies have shown that acid purification also leads to partial oxidation of CNT themselves and sometimes to an extensive disruption of the tubular structure, especially in the case of single-walled carbon nanotubes (SWCNT). Here we report on the use of steam for the purification and opening of CNTs. Steam allows a better control of the removal of the carbonaceous fragments, neither functionalizing the SWCNTs nor damaging their tubular structure (as confirmed by IR and Raman spectroscopies) Addition of an aqueous solution of uranyl acetate to the purified CNTs gives uranyl acetate@CNTs, which provides direct evidence of the opening of the CNT ends. The uranium was chosen simply because it is easy to detect using HRTEM. The steam purified samples, free of amorphous carbon can then be readily functionalized on the sidewalls.