  Single-walled carbon nanotubes (SWNTs) are potential materials for future
nanoelectronics. Since the electronic and optical properties of SWNTs strongly
depend on tube diameter and chirality, obtaining SWNTs with narrow (n,m)
chirality distribution by selective growth or chemical separation has been an
active area of research. Here, we demonstrate that a new, bimetallic FeRu
catalyst affords SWNT growth with narrow diameter and chirality distribution in
methane CVD. At 600C, methane CVD on FeRu catalyst produced predominantly (6,5)
SWNTs according to Uv-vis-NIR absorption and photoluminescence
excitation/emission (PLE) spectroscopic characterization. At 850C, the dominant
semiconducting species produced are (8,4), (7,6) and (7,5) SWNTs, with much
narrower distributions in diameter and chirality than materials grown by other
catalysts. Further, we show that narrow-diameter/chirality growth combined with
chemical separation by ion exchange chromatography (IEC) greatly facilitate
achieving single-(m,n) SWNT samples, as demonstrated by obtaining highly
enriched (8,4) SWNTs with near elimination of metallic SWNTs existing in the
as-grown material.
