Japanese computer giant NEC Corp. (Tokyo) has developed a technology to mass produce nano carbon materials in a horn-shaped structure. Because of their shape and the absence of metallic impurities, the so-called carbon nanohorns may have applications in drug-delivery systems.
Carbon nanohorns measure approximately 2 to 5 nm in diameter and 40 to 50 nm in length. Several thousand can be assembled into a spherical shape that is approximately 100 nm in diameter with a wide surface area per unit mass. This structure enables easy dispersion and high conductivity; capacitors, actuators and fuel cells are among the primary applications. Since metal catalysts are not used in the fabrication process, the carbon nanohorns are free from metallic impurities, making them suitable for use as drug-delivery devices, as well. A variety of tests carried out on cells and in vivo have detected no short-term toxicity. Moreover, their 100-nm spherical structure has no negative impact on surrounding cells or tissues, according to the company.
Carbon nanohorns were first discovered in 1998 by a research team led by NEC Senior Research Fellow Sumio Iijima, but producing high-purity carbon nanohorns in large volumes has been problematic. Pulsed laser ablation technology helped NEC to overcome this challenge and produce 1 kg of 95%-pure carbon nanohorns per day. Because they can be fabricated at room temperature and under normal atmospheric conditions, production costs are lower than for the manufacture of other nano carbon materials, the company says.
NEC has secured a basic patent to produce carbon nanohorns for commercial use.