The present invention is generally directed to methods of ozonating CNTs in fluorinated solvents (fluoro-solvents), wherein such methods provide a less dangerous alternative to existing ozonolysis methods. In some embodiments, such methods comprise the steps of: (a) dispersing carbon nanotubes in a fluoro-solvent to form a dispersion; and (b) reacting ozone with the carbon nanotubes in the dispersion to functionalize the sidewalls of the carbon nanotubes and yield functionalized carbon nanotubes with oxygen-containing functional moieties. In some such embodiments, the fluoro-solvent is a fluorocarbon solvent, such as a perfluorinated polyether.