Abstract

Nanotubes are special nanoparticles in several senses. Opposed to most tiny objects that tend to adopt a spherical shape with only one geometrical parameter (the average radius), hollow cylindrical objects have an immediate advantage over spheres as they possess three independent geometrical parameters: length L, external radius R, and internal radius a, as illustrated in Figure 14.1. Moreover, in some cases the inner and outer surfaces are electrically polarized in the opposite sense so they have a different affinity toward foreign atoms, allowing for diverse functionalizations (Mitchell et al. 2002). Magnetic nanotubes have still another advantage over the rest of the nanotubes: they can be driven to the point of interest by means of externally applied magnetic fields. This is true whether the application of the magnetic nanotube is on a semiconductor chip or is intended to reach an ill organ of a living body for drug delivery.