In addition to that, the presence of particles prevents the selective reaction of internal nanotubes, and this issue of purity confuses nanotubes based on their size, type, or use as macromolecular species. Absorption spectroscopy (NIR-Vis-UV) can be used to check the population of the sample or the degree of grouping of the sample. If how to distribute nanotubes by NIR-Vis-UV absorption spectroscopy is desired, the sample should be dispersed or in the form of a thin layer. Optical absorption measurements provide (...) useful information about the electronic properties of SWCNTs, and this information can be used to study covalent and non-covalent interactions between molecules and nanotubes. (shrink)