US Patent 7261941 - Carbon nanohorn with directed tip

http://www.freepatentsonline.com/7261941.html

Carbon nanotubes aggregates having conical tips are referred to as carbon nanohorns. This patent from NEC teaches a carbon nanohorn with a acute angle directed tip for improved uses in applications such as carbon based electron emission. Sumio Iijima, who is credited as having first recognized carbon nanotubes in 1991, is noted as a co-inventor. Claim 1 reads:

1. An acute closed tip, multi-wall carbon nanotube radial aggregate, which includes a plurality of acute tip, multi-wall carbon nanotubes which each have one sharp, acute angled-end and are radially aggregated with the acute tip portion thereof being disposed outward.