8. Conclusions and Further Outlook

The field of carbon nanotubes continues to be one of the hottest topics in the nanoscience and nanotechnology, so the development of their functionalization and dispersion methods is and will be an important research area, at least for the next 10 years. A series of contemporary techniques are being used for CNT solubilization, from physical (classic ultrasound, plasma treatment, UV light, dielectrophoresis [1, 2], gel electrophoresis [3, 4], density-gradient ultracentrifugation [5, 6], irradiation techniques, and chromatography [7], among others) to chemical and biological, applying inorganic (other carbon allotropes, iodine, bromine, metallic sodium in liquid ammonia, CO₂, peroxides, ozone, metal salts, and mineral acids) and organic (acids, salts, polymers, dyes, natural products, in particular diazonium salts [8]; functionalization with porphyrins, amines, pyrene, polymers, sugars, etc.) compounds and biomolecules (DNA, peptides, amino acids, etc.), as well as micelles on their basis and some metal complexes. CNTs can be functionalized by oxidation (peroxy acids; metal oxidants, such as osmium tetroxide, potassium permanganate, chromates; ozone; oxygen; superoxides) or reduction reactions (interactions with thiols, carbenes, dienes, etc.).