Temperature-dependent growth of 36 inner nanotubes inside nickelocene, cobaltocene and ferrocene-filled single-walled carbon nanotubes

Abstract

We have investigated the effects of temperature, diameter and metal catalyst type on the growth of inner nanotubes inside metallocene-filled single-walled carbon nanotubes (SWCNTs). The effects on the yield of different chiralities of inner nanotubes were scrutinized by multifrequency Raman spectroscopy. The investigated diameters range from ~0.7 to 1.3 nm and comprise 36 distinct chiralities. For all three investigated metals (Ni, Co, Fe), there is a linear correlation of growth temperature with nanotube diameter. The common slope for these metals is found to be 40.5◦ C/Å. The temperature difference between the largest and the smallest diameter tubes amounts to ~230◦ C for all three precursors. The growth temperatures are offset by 34◦ C from Ni to Co and another 28◦ C from Co to Fe. The quantified correlations of temperature, diameter and metal catalyst type provide the basis for engineering the diameter-specific growth of nanotubes.