Keywords: carbon nanotubes, morphology, dielectrophoresis, conductance, iron nanoparticles, CVD, ferrocene, iron (II) phthalocyanine, nanotechnology
Multi-walled carbon nanotubes synthesised from different catalysts: morphology, dielectrophoresis and conductance
We give a brief overview of research to date on carbon nanotubes in New Zealand. We then present an investigation of the relationship between morphology and conductance and other properties of multi-walled carbon nanotubes (MWCNTs) synthesised under identical conditions using different catalyst precursors, namely ferrocene and iron (II) phthalocyanine. Large differences were observed in the morphology, the composition, the thermal stability with respect to oxidation and the Raman spectra of the MWCNTs from the two precursors. We focus on the assembly of MWCNTs in an AC electric field (dielectrophoresis). The AC response of the field-collected MWCNTs indicated that both sorts of MWCNT showed high polarisability, but surprisingly, only the more disordered MWCNTs grown from ferrocene-derived catalyst formed conducting paths between the electrodes. Our results suggest that that the formation of highly-conducting electrical contacts between the ferrocene-derived MWCNTs and electrodes is favoured by their greater Fe content. We suggest that Fe nanoparticles act as 'nanoshorts' between neighbouring MWCNTs and between MWCNTs and electrodes.