The impact of ferrocenium as a catalyst on the chiral distribution of single-walled carbon nanotubes in floating-catalyst chemical vapor deposition synthesis

In response to the growing demand for novel catalyst designs for the selective growth of single-walled carbon nanotubes (SWCNTs), this study explores the use of ferrocenium (the oxidized state of ferrocene) as a new catalyst precursor for the first time. Utilizing the floating-catalyst chemical vapor deposition (FC-CVD) method, SWCNTs were synthesized and characterized through analytical transmission electron microscopy selected area electron diffraction (TEM SAED) and optical techniques (Raman spectroscopy and UV-vis-NIR absorption). The introduction of ferrocenium led to an enhancement in the metallicity of the nanotubes, increasing the proportion of metallic SWCNTs to 43.1%, while also broadening the nanotube mean diameter from 1.84 nm to 2.10 nm. The key factor behind this improvement lies in the positive charge of Fe³⁺ in ferrocenium, which has been shown to stabilize metallic nanotube formation. These findings highlight the pivotal role of catalyst charge in controlling SWCNT chirality and electronic properties, paving the way for more precise control in nanotube synthesis for applications in nanoelectronics and materials science.