Covalent bonds nanostructure materials

As far as the chemist is concerned, nanosized materials are huge macromolecules (with molecular weights of the order of 106 to 1010) constructed from millions of atoms. Atom-by-atom synthesis of nanostructures, via covalent bond formation, is a formidable task which has not as yet been achieved by synthetic chemists. Covalent polymerization is the best that chemists have done thus far [3]. Chemists have made spectacular progress, however, in forming self-organized and supramolecular materials in the size domain of nanostructures by the non-covalent bond assembly of molecules [7]. 

The non-specific adsorption of proteins on carbon nanotubes is an interesting phenomenon but represents a relatively less controllable mode of protein-CNT interaction. Moreover, in non-covalent immobilization process, the immobilized protein is in equilibrium between the surface of the carbon nanotubes and the solution and can therefore be gradually detached from the nano-material surface, a phenomenon called protein leakage [127]. To prevent the leaching of enzymes, covalent bonds have been used to attach the enzyme molecules to the nanostructured materials, which lead to more robust and predictable conjugation. Experimental evidences prove that proteins can be immobilized either in their hollow cavity or on the surface of carbon nanotubes [130]. 

Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical nanostructure. They have a Young s modulus within the range 270-950GPa, a tensile strength of 11-63 GPa,and a density of 1.3-1.4g/cm Their outstanding mechanical properties originate from the covalent bond between the adjacent carbon atoms, which enables this material to be used for the fabrication of the next generation of body armour. 

Since the surface of nanostructures has low reactivity, for increasing the nanostructure surface activity functionalization is used, that is, the attachment of certain atoms of sp- or d-elements to the atoms on the nanostructure surface and the formation of a covalent bond between them the functionalization results in the formation of an interlink between the atoms of the nanostructure surface and the atoms of material. 

---