A study on the action of ozone on multiwall carbon nanotubes

The functionalization of the surface of multiwall nanotubes (MWNTs) is the first step for the synthesis of more complex supramolecular structures and for their application by attaching molecules, macromolecules and biologically active molecules. Here we show in detail a couple of methods for introducing oxygenated surface groups on MWNTs by room temperature ozonization. The reaction kinetics between MWNTs and O-3 has been studied in static conditions inside an IR gas cell. The pseudofirst order rate constant has been determined and compared with those of other carbon materials. MWNTs appear as the most reactive carbon materials with ozone, producing CO2 and even CO in certain special conditions when treated with a stream of ozonized oxygen. The ozonization reaction is strongly exothermic and conforms to the Elovich equation, an equation normally employed for the gas-solid oxidation kinetics and the chemisorption of gases over solid surfaces. The ozonized MWNTs have been characterized qualitatively by FT-IR spectroscopy and different types of ketonic groups have been detected although the most common has been found the carboxyl moiety. The quantitative analysis of ozonized MWNTs has been made by thermogravimetric analysis under N2 flow.