A salt-driven mechanism for precise chirality sorting of carbon nanotubes

Abstract

Sorting single-wall carbon nanotubes (SWCNTs) by chirality/handedness is of substantial scientific and technological importance. Existing sorting methods often lack simplicity, reproducibility and scalability. Here, we demonstrate a salt-driven SWCNT sorting mechanism that addresses these challenges. Various polyethylene glycol (PEG)/salt aqueous two-phase systems effectively modulate the top-phase partitioning of DNA-wrapped SWCNTs (DNA-SWCNTs) across a broad range of hydrophobicities, with cation composition markedly affecting top-phase partitioning in the order NH₄⁺ > K⁺ > Li⁺ > Na⁺ closely resembles the well-documented Hofmeister series. We designed PEG/salt systems with defined [K⁺]:[Na⁺] cation ratios to precisely regulate SWCNT partitioning, enabling one-step top-extraction of multiple single-chirality SWCNTs. The cation ratio parameter, determined in small-scale experiments, remains effective at scales 200 times larger, allowing one-step, milligram-scale separation of (−) (6,5) with record-high enantiomeric purity. In addition, we develop a salt-switching multistage bottom-extraction strategy to isolate (+) (6,5) enantiomer. Our method uses simple salts to provide an easy-to-implement, high-precision, scale-invariant, and cost-effective platform for routine SWCNT chirality sorting.