Highly Efficient Sorting of Carbon Nanotubes via Ammonium-Salt Functionalized Silica Micro Colloids

Semiconducting single-walled carbon nanotubes (s-SWNTs) possess the potential to surpass silicon in next-generation integrated circuits (ICs). This advantage stems from their unique quasi-one-dimensional ballistic transport structure, which results in weak charge scattering, high carrier mobility, and long mean free paths. However, achieving efficient and ultrapure separation of s-SWNTs from metallic SWNTs (m-SWNTs), while simultaneously removing short SWNTs, remains a significant challenge. Here, we present an effective method for the efficient separation of m-SWNTs/s-SWNTs and the sorting of short/long SWNTs using ammonium-salt functionalized silica micro colloids (SMCs). The approach leverages the higher affinity of ammonium groups toward m-SWNTs rather than s-SWNTs, enabling isolation of s-SWNTs with >99.999% purity. Additionally, owing to their higher kinetic energy, short SWNTs rapidly absorb onto the surface of the SMCs, leaving longer SWNTs in solution. This selective adsorption process increases the average length of the SWNTs remaining in solution by approximately 4-5-fold after separation. Furthermore, our method is effective for both organic- and aqueous-phase SWNT dispersions. This work provides an effective strategy for obtaining ultrapure and length-sorted s-SWNTs, which is critical for fabricating high quality materials required in next-generation large-scale ICs.