The use of organometallic transition metal complexes in the synthesis of shaped carbon nanomaterials

A review of the use of organometallic complexes in the synthesis of shaped carbon nanomaterials (SCNMs), in particular carbon nanotubes (CNTs) has been undertaken. This review reveals that a limited number of organometallic complexes have been used as catalysts (typically ferrocene, Fe(CO)₅) to make carbon materials that have distinctive shapes. Depending on the reaction conditions employed, ferrocene can be used to synthesize single walled (SWCNTs), double walled (DWCNTs) and multiwalled nanotubes (MWCNTs) as well as fibres and other SCNMs. The type of reactor used as well as the reaction conditions (temperature, pressure, gas flow rates, etc.) and the presence of hydrogen and heteroatoms (N, O, S, P, etc.) also play a role in determining the final carbon types (and their sizes) that have been synthesized. The influence of the various chemical and physical factors on the carbons produced are discussed. The current mechanism used to explain the formation of CNTs is described.