Synthesis of Butterfly-Like Amphiphiles and Dispersion of Multiwalled Carbon Nanotubes in Aqueous Solutions

The dispersion of carbon nanotubes (CNTs) is crucial for further their applications in biocompatible nanodevices. A series of nonionic Gemini amphiphiles containing pyrene groups, denoted as PyE_n (where <i>n</i> = 12, 18, and 22), were synthesized to facilitate the dispersion of multiwalled carbon nanotubes (MWCNTs) in aqueous solutions. Compared to conventional single-chain surfactant Triton X-100 (TX-100), PyE₁₈-modified MWCNTs (PyE₁₈@MWCNTs) exhibited superior dispersing capability due to enhanced π-π interactions. The characterization of PyE₁₈@MWCNTs through various techniques revealed the presence of π-π stacking interactions among the pyrene moieties and surfaces of nanocarbon tubes. The structural integrity of MWCNTs was maintained after the modification, as evidenced by Raman spectroscopy. Furthermore, PyE₁₈-modified MWCNTs demonstrated improved hydrophilicity compared with the original MWCNTs and remained stable in aqueous solutions for over 90 days. The contact angle between the modified MWCNTs film and the aqueous drop decreased from 140° to less than 30°. These findings illustrate the significance of polyaromatic structures in the development of efficient dispersants for carbon-based materials such as CNTs, graphenes, and fullerenes.