Overcoming van der Waals Bundling: Molecular Wedges Enable Sonication-Free Dispersion of Single-Walled Carbon Nanotubes.

Abstract

Single-walled carbon nanotubes (SWCNTs) naturally bundle due to strong van der Waals interactions, posing a significant challenge to their dispersion and applications. Conventional methods require ultrasonication or extended shear mixing, which are energy-intensive, can damage the nanotubes, and/or incur high process costs and low throughput. Here, we show that small molecular wedges, which are formed by reacting wedge precursors (e.g., 1-octanol, ammonia, <i>n</i>-hexylamine) with minimal amounts of superacids (e.g., chlorosulfonic acid, CSA), can intercalate the nanotube bundles, markedly reducing van der Waals interactions. Modeling based on the Euler-Bernoulli beam theory reveals a relationship between the pry-open length and the molecular wedge size, adhesion energy, and the nanotube's bending stiffness. Wedged SWCNTs exhibit a 130-fold increase in dispersion efficiency with DOC and a 14-fold increase with single-stranded DNA, all while preserving the nanotube length. Even in organic solvents, where gentle stirring typically yields almost no dispersion, the wedging approach achieves a dispersion yield of (6,5)-SWCNTs up to ∼2.7% (O.D. ∼13). Furthermore, this method enables one-pot sp³ quantum defect functionalization with improved uniformity and modulates defect photoluminescence by replacing defect-pairing groups with wedges. This versatile wedging approach provides a scalable route for processing SWCNTs and is expected to be broadly adaptable to other van der Waals materials.