Tailored Degree of Functionalization and Length Preservation of Multiwalled Carbon Nanotubes by an Optimized Acid Treatment Process

The introduction of oxygen groups in carbon nanotubes is considered crucial for many applications. However, there is a lack of controlled functionalization methods which ensure nanotubes with specific property values according to each interest. In this work, acid treatments of multiwalled carbon nanotubes (MWCNTs) employing an optimized ultrasound process with moderate heating and stirring were studied by means of a factorial design. The functionalized nanotubes were characterized by thermogravimetry, elemental analysis, Raman spectroscopy, electron microscopy and water stability tests. Statistic models were fitted for the degree of functionalization and length reduction of MWCNTs. Temperature was identified as a key parameter to produce more functionalized MWCNTs with less structural damage. The properties of the functionalized MWCNTs can be tailored by the choice of parameters exploited in the statistical models developed to enable different end-use requests, such as for polymeric composites or bio-related applications, which is the original contribution of this work.