Carbon Nanohorns and Their High Potential in Biological Applications

Abstract

Carbon nanohorns, also called single-wall carbon nanohorns (SWNHs), are single-graphene tubules with horn-shaped tips, and were first reported by Iijima and colleagues in 1999 [1]. The tubule lengths and diameters range from 30 to 50 nm and 2 to 5 nm, respectively, and therefore, SWNHs are not uniform in size. Thousands of SWNHs assemble to form an aggregate, which in turn has an average diameter of ~80–100 nm. SWNHs are produced in large quantities (1 kg/day) by laser ablation of graphite. This process does not require a metal catalyst, and thus it is possible to prepare SWNHs with high purity (>95 %). Owing to their large surface area, molecular sieving effects and photo-thermal conversion characteristics, SWNHs show promise for applications in gas adsorption and storage, biosensor and nanomedicine such as drug delivery and photo-hyperthermia cancer therapy. In this chapter, we briefly introduce nanohorn production methods, biomaterial properties, and functionalization, and then highlight the potential use of SWNHs in various biological research fields. Issues concerning toxicity and biodegradation are also discussed.