Solvent-Free Functionalized Boron Nitride Nanotubes via Open-Air Cold Plasma for Highly Stable Dispersion in Water

Abstract

For the dispersion of boron nitride nanotubes (BNNTs), noncovalent or covalent functionalization methods in a solvent with complex procedures, including acidic treatments, are widely used. Herein, we propose a solvent-free functionalization of BNNTs using a facile atmospheric-pressure cold-plasma treatment method. The plasma-treated BNNTs exhibited nearly threefold enhanced dispersibility and fourfold improved long-term dispersion stability compared with pristine BNNTs. These remarkable enhancements were attributed to the presence of the O atoms and OH molecules generated in the plasma, which reacted with the BNNT surface to form B−N−O and OH bonds. Consequently, the wettability of the plasma-treated BNNTs was transformed to superhydrophilicity, resulting in the exfoliation of the BNNT bundles in water. Small-angle X-ray scattering measurements confirmed the successful exfoliation of plasma-treated BNNTs from bundled structures in water. From an application perspective, the atmospheric-pressure cold plasma method offers a solvent-free, straightforward, and robust approach for BNNT functionalization, eliminating the need for additional post-procedures to remove residual surfactants from BNNTs.

Facile covalent functionalization of boron nitride nanotubes via coupling reaction

“…8 presents the results of a long-term stability assessment of the functionalized BNNT (3a–3g), as well as BNNT analyzed using the absorbance value from UV-Vis spectra. 55 All analyses ( Fig. 8a–d ) exhibit a consistent trend: pristine BNNT solutions degrade in stability more rapidly than functionalized BNNT under identical measurement conditions.…”