ABSTRACT
Depending on the number of graphene layers from which a single carbon nanotube (CNT) is composed, CNTs are classified as single-walled carbon nanotubes and multiwalled carbon nanotubes. CNTs have been studied for applications in a wide variety of areas, including composite materials, nanoelectronics, field-effect emitters, hydrogen storage, etc. Surface functionalization of CNTs can be covalent or noncovalent. CNT oxidation has been carried out with oxidizing Applications of Carbon Nanotubes in Biosensing and Nanomedicine agents such as nitric acid. Although oxidized CNTs are soluble in water, they aggregate in the presence of salts due to charge screening effects, and thus may not be quite suitable for biological applications due to the high salt content of most biological solutions. Various amphiphiles have been used to suspend CNTs in aqueous solutions, with hydrophobic domains attached to the CNT surface via van der Waals forces/hydrophobic interaction and polar heads for water solubility. The pyrene derivative-modified CNT surface can also be used for further functionalization.
