Quality Assessment of Bulk Boron Nitride Nanotubes for Advancing Research, Commercial, and Industrial Applications

Evaluating the quality of nanomaterials is essential for both basic research and industrial applications. Here, we describe a methodology for assessment of relative quality of boron nitride nanotube (BNNT) materials by absorption spectroscopy of regiorandom poly(3-hexyl-thiophene) (rra-P3HT) aggregates on BNNTs dispersed in chloroform. The strong selective π–π interaction between rra-P3HT and nanotubes combined with distinctive visual and spectroscopic changes allows a practical procedure for relative evaluation of BNNT external surface area and surface quality. The method calls first for the identification of the sample-specific polymer loading saturation point, which corresponds to the maximum BNNT surface polymer coverage in the sample. The sample quality (defined as the combination of sample purity and BNNT wall defect density) is determined from the structure and intensity of the absorption spectrum which depend on the morphology and the total amount of rra-P3HT adsorbed on BNNT samples. This methodology for quality assessment is critical for accelerating the development of new, efficient purification strategies for bulk BNNT materials and advancing the investigation of BNNT properties and industrial applications.