Engineering the surface of carbon-based nanomaterials for dispersion control in organic solvents or polymer matrices

The surface modification of carbon-based nanomaterials, including carbon nanotubes (CNTs) and graphene oxide (GO), is advantageous for tailoring their dispersion in different solvents, as well as polymer matrices. Although the surface modification methodology of such nanomaterials is well established, the relationship between functionalization and interaction with the surrounding environment (solvents or polymers) - particularly repulsion/attraction forces that govern the clusters' formation - is still not well understood to date. Herein, the dispersion of pristine and oxygenated/amino-functionalized CNTs and GO in different solvents were studied qualitatively (by optical microscopy and visual observations of dispersion tests) and quantitatively (by UV-Vis spectroscopy), and the repulsion/attraction process was explained based on pi-pi{*} transitions between CNT or GO and solvents. We found that both CNT and GO can have good dispersion in water, N-methyl-2-pyrrolidone (NMP), and N,N-dimethylformamide (DMF), and the key to this behavior is the precise functionalization control, including orientation and type of functional group. In this sense, the introduction of functional groups improves the interaction quality of CNT and GO due to nanoscale attraction, and at the same time, enhances their orientation due to steric effect. The present study is expected to contribute to carbon-based nanomaterials' surface engineering, which may be useful for researchers from different fields, such as carbon nanostructures, materials chemistry, and polymer nanocomposites. (AU)