Synthesis, Characterization, and Applications of Surface Modified Carbon Nanotubes

Carbon nanotubes (CNTs) are superior to other materials in the field of material chemistry due to potential applications in technology and nanoscience. CNTs are considered nano–pharmaceuticals due to their importance in the fields of diagnosis, tissue regeneration, as well as in drug targeting, and drug delivery. The toxicity due to the hydrophobic surface of CNTs, availability of non-uniform structure & morphology, large surface area, and insolubility in an aqueous medium are the main restrictions that limit the use of CNTs in the field of nano-medical. Functionalization or surface modification removed all these restrictions. Surface modification of carbon nanotubes by introducing desirable functional groups enhances their use in nano-medical, which improves the blending of CNTs with biological systems. Surface modification of CNTs improves their compatibility and solubility; thus, surface-modified CNTs play a crucial role in finding applications in various fields. Surface functionalization categorizes into exohedral and endohedral. The changes made on the outside or inside walls of CNTs are the basis of surface functionalization. Noncovalent modification in molecules leads to physically bounding on the molecular surface, whereas in covalent modification, polymer chains are grafts on the surface of the CNTs. Covalent and noncovalent interactions can do exohedral functionalization. Thus, the type strategy adopted for the surface modification of nanotubes depends on the type of linkage found between the carbon nanotubes and functional groups. Endohedral functionalization involves incorporating metals, fullerenes, and halogens on the inside walls of CNTs. Surface analysis techniques like scanning probe microscopy, electron microscopy, infrared spectroscopy, atom probe analysis, temperature-programmed desorption, etc., are generally employed to characterize the surface modified CNTs. Surface modification of CNTs enhances their solubility and affinity in organic solvents as well as functionality which improves the utility of surface-modified CNTs in the variable fields of biomedical science, materials science, drug delivery systems, and water purification.