Dispersion of boron nitride nanotubes in aqueous solution by simple aromatic molecules

We report that the simple aromatic molecules successfully disentangle and disperse multi-walled boron nitride nanotubes (BNNTs) in aqueous solutions through pi-pi stacking interactions. Aromatic molecules such as derivatives of naphthalene, anthracene, and pyrene were used as dispersants and components for construction of nanohybrids. Spectroscopic analyses of water-dispersed BNNTs revealed that not only numbers of aromatic rings but also substituted functional groups were essential for dispersion capabilities. It was suggested that greater numbers of aromatic rings and a carboxylic acid as the substituted group showed higher dispersion capabilities among the molecules used in this study. Detailed microscopic analyses using atomic force microscopy and transmission electron microscopy showed certain isolation capabilities of the aromatic molecules for BNNTs in aqueous solution. Moreover, fluorescence spectra indicated that BNNTs and the aromatic molecules have different electronic states after hybrid formation. Our results using the simple aromatic molecules will be utilized as a basic data for dispersion of BNNTs and construction of disentangled BNNT nanohybrids effectively.