Tailoring the Chemistry and Morphology of Vertically Aligned Carbon Nanotubes Forests, Implications for Smart Electrodes

Vertically aligned carbon nanotubes (VACNT) combine three advantageous traits: immense specific surface area, excellent thermal and electric conductivities, and controllable directionality. Thus, VACNT attract attention for anisotropic nanocomposites useful in applications such as supercapacitors, transistors, water purification, thermal management, and dry adhesives. The varying waviness, and high anisotropy VACNT hinders adhesion and therefore processability, thus requires adjustment. Because VACNT structures are susceptible to capillary forces, most wet surface treatments become impractical, leaving only gas-based methods as viable options. The field of gas-based VACNT surface treatment is underdeveloped, with limited control over processes outcome. The introduced methodology enhances the process controllability, enabling gently adjusting the oxygen content on VACNT nanotube surfaces, as well as their nanomorphology and entanglement. The samples are gradually heated to between 430 and 500 °C to weaken the C-C bonds without really breaking them, enabling their adjustment, by introduction of either air or Ar through the reactor. Argon causes removal of excess oxygen contamination and nanotubes straightening, while air enables introduction of additional oxygen functional groups. This method augments the nanocomposite homogeneity, enhancing accessibility towards more active sites for current application performance, amplifying biomedical sensing signal, catalytic activity and heat dissipation. Additionally, by introduction of other gases, unfulfilled predictions could be enabled, and the current state-of-the-art can be expanded.