Biocompatible ionic liquids as stabilizers and dispersing solvents of multi-walled carbon nanotubes: A comparable study of stable composites between imidazolium and cholinium

This research explores the dispersion and stabilization of functionalized multi-walled carbon nanotubes (fCNTs) using ionic liquids (ILs) with varying concentrations of both fCNTs and ILs. In this work imidazolium-based ILs (1-butyl-3-methylimidazolium chloride [Bmim][Cl] and 1-butyl-3-methylimidazolium acetate [Bmim][Ac]) and cholinium-based ILs (choline chloride [Ch][Cl] and choline acetate [Ch][Ac]) were utilized to understand the impact of different ILs molecular structures on MWCNT dispersion. Techniques such as UV–visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and transmission electron microscopy (TEM) were employed to analyze the ILs-MWCNT composites. The results indicate that MWCNT concentration significantly affects their interaction with ILs at 0.025 mg/mL of fCNTs being optimal for imidazolium-based ILs. Higher IL concentrations (0.5 and 1.0 mg/mL) were found to be less effective. Imidazolium-based ILs were more effective than cholinium-based ILs in dispersing of fCNTs, due to cation–π or CH–π interactions between imidazolium cations and the π-electron network of fCNTs. The formation of nano-IL-based composites was confirmed by a new absorption band around 225 nm in the UV–visible spectra. The stability in the absorbance peak suggests that the interaction between the ILs and fCNTs forms a stable complex that does not undergo significant changes or degradation for long-time, which makes them suitable for long-term use in various technological and industrial applications. This finding highlights the robustness of the IL-MWCNT interaction and underscores the potential of these materials for applications requiring stable and durable nanomaterial dispersions. This study sheds light on the mechanisms governing carbon nanotube (CNT) dispersion in aqueous solutions and emphasizes the importance of IL cationic components in optimizing MWCNT dispersion and stabilization.