One property of nanotubes is that they’re really, really strong. While bundling strongly affects photoluminescence, it has much weaker effect on optical absorption and Raman scattering. Their electrons can be excited, thus resulting in optical absorption, but the holes are immediately filled by other electrons out of the many available in the metal. Consequently, sample preparation for the latter two techniques is relatively simple. Tensile strength is a measure of the amount of force an object can withstand without tearing apart.
In particular, the band gap can vary from zero to about 2 eV and the electrical conductivity can show metallic or semiconducting behavior. Many properties of single-walled carbon nanotubes depend significantly on the (n,m) type, and this dependence is non-monotonic (see Kataura plot). Pristine carbon nanotubes are inert to most chemicals and need to be grafted with surface functional groups to increase their chemical reactivity and add new properties. The way those materials interact with electromagnetic radiation is unique in many respects, as evidenced by their peculiar absorption, photoluminescence (fluorescence), and Raman spectra. Spectroscopic methods offer the possibility of quick and non-destructive characterization of relatively large amounts of carbon nanotubes, yielding detailed measurements of non-tubular carbon content, tube type and chirality, structural defects, and many other properties that are relevant to those other applications.Interactions between nanotubes, such as bundling, broaden optical lines. There are two things that account for this strength. Other current applications include:Current research for modern applications include:The fact is, Radushkevich and Lukyanovich [..] should be credited for the discovery that carbon filaments could be hollow and have a nanometer- size diameter, that is to say for the discovery of carbon nanotubes.An infinite nanotube that is of the zigzag (or armchair) type consists entirely of closed zigzag (or armchair) paths, connected to each other.Here are some unrolled nanotube diagrams:Degenerate "zigzag" tube type (1,0)It follows that the circumference of the tube and the angle of the strip are not arbitrary, because they are constrained to the lengths and directions of the lines that connect pairs of graphene atoms in the same class.Nanotube of the (2,2) type, the narrowest "armchair" onePossibly degenerate chiral tube type (2,1)Here are some tube types that are "degenerate" for being too narrow:Nanotube of the (3,0) type, the narrowest "zigzag" oneDegenerate "armchair" tube type (1,1)Degenerate "zigzag" tube type (2,0)which must evaluate to integers.Chiral nanotube of the (3,1) type.Chiral nanotube of the (1,3) type, mirror image of the (3,1) type.