Precise and Scalable Depletion-Based Length Separation of Carbon and Boron Nitride Nanotubes

Published

August 28, 2024

Author(s)

Pavel Shapturenka, Benjamin Barnes, Matthew Noor, Jeffrey Fagan, Elisabeth Mansfield

Abstract

Partitioning rod-like particles by shape and critical dimension yields a rich platform for investigating fundamental anisotropic colloidal interactions, establishing rigorous metrological standards for emerging nanomaterials, and advancing technological frontiers. Herein, we present investigations of entropically driven polymer-induced precipitation of highly purified single-wall carbon nanotubes (SWCNTs) and boron nitride nanotubes (BNNTs) for large scale and tunable length separation. Results are presented from four distinct nanotube populations of increasing average diameter (0.7 to >2 nm) and stiffness, produced by different synthesis methods, and progressively fractionated in a "reverse sequential" precipitation scheme by addition of a polymer depletant. The resulting populations were characterized through analytical ultracentrifugation, optical spectroscopy, and atomic force microscopy, enabling cross-comparison of length separation fidelity and distributions, and across diameter/material space for applied polymer concentrations. Strong fractionation by length was achieved in all populations, with obtained mass-weighted average lengths of 200 nm up through >1 micron. Kinetic parameters were empirically determined to be significant, especially for reducing contamination of longer nanotubes in shorter populations. For BNNT materials, the precipitation was furthermore found to yield shape selection, significantly removing non-tube mass in the earliest fractions. Finally, a clear trend of increasing average precipitated SWCNT length with decreasing diameter was observed, indicating changes in excluded-volume interactions stemming from the increased flexibility of narrower nanotubes. The extended variety and degree of precise control over nanotube populations offers an improved model system for theoretical benchmarking of self- and directed assembly behavior and extends the scale and capability of nanotube implementation within the low-dimensional nanomaterial community.

Citation

RSC Advances

Pub Type

Journals

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Keywords

Nanotubes, nanomaterials, colloids, polymers, depletion forces, separation science, spectroscopy

Citation

Shapturenka, P. , Barnes, B. , Noor, M. , Fagan, J. and Mansfield, E. (2024), Precise and Scalable Depletion-Based Length Separation of Carbon and Boron Nitride Nanotubes, RSC Advances, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=956589 (Accessed September 30, 2025)