Dispersion Stability of MWNTs by Effective Functionalization

Abstract

The aim of this project was to investigate methods for purification and modification of Multi Wall Carbon Nanotubes. Covalent and non-covalent approaches to functionalization were studied. The undesired dispersion stability of carbon nanotubes in water and organic solvents is a challenging task for their utilization in nanoscale devices e.g, thermal conductive paste. Multiwalled carbon nanotubes (MWNTs) have been tested with different chemical functionalities of the side groups for their dissolution in organic solvents or water. Herein, we investigated the dispersive effects achieved by surface-active agents on MWNTs. Dodecyl trimethylammonium bromide (DTAB) and Sodium octanoate (SOCT) were found to form exceptionally stable MWNT dispersions. In this study, a novel method was developed to prepare highly dispersed MWNTs using the mixtures of cationic surfactant DTAB and anionic surfactant SOCT. It was found that these surfactants in mixtures gave stable dispersions at much low total surfactant concentration as compared to their concentration when used alone.

The dispersibility, structure and morphological properties of modified tubes were characterized by Raman and SEM. Zeta measurement and TEM were further employed to characterize the interaction between nanotubes and non-covalent modifiers.

The effects of five different purification methods on the dispersibility, and degree of carboxylic acid functionality of MWNTs, along with the level of defects on the tube side walls, and the resulting electronic properties of MWNTs have been investigated.