High-purity single-molecule modification of carbon nanotubes by stochastic distribution of DNA

Single-walled carbon nanotubes (SWCNTs) show promise for probing molecular interactions at single-molecule resolution, but precise and uniform surface modifications needed for single-molecule SWCNT applications remain challenging due to the stochastic nature of chemical reactions. This study presents a batch-scale synthesis and separation of single-molecule modified SWCNTs, leveraging the stochastic distribution of single-stranded DNA (ssDNA) on SWCNTs and biology-inspired separation strategies. Specifically, SWCNTs were dispersed with ssDNA mixed with a small fraction of decorated ssDNA (m-ssDNA). We developed a stochastic ssDNA-SWCNT binding model to predict the distribution of ssDNA and m-ssDNA on SWCNT at distinct mixing ratios and successfully implemented our model to produce SWCNT nanoparticles predominately containing only one m-ssDNA tag. These singly modified SWCNTs were isolated from unmodified SWCNTs using magnetic bead exploiting biotin-streptavidin interactions, achieving 0.05 μg yield at 0.25% m-ssDNA ratio, corresponding to 97.6% purity of singly modified populations. Finally, the single-molecule modification at the predicted m-ssDNA ratios was confirmed using a fluorophore as a model, enabling precise determination of SWCNT molar concentration. Ultimately, our approach provides a batch-scale method for incorporating a single molecular tag per SWCNT, supporting diverse future applications in SWCNT-based nanotechnologies.