High‐Purity Monovalent Functionalization of Carbon Nanotubes

Single‐walled carbon nanotubes (SWCNTs) show promise for probing molecular interactions at single‐molecule resolution, yet generating SWCNT populations bearing a single defined functional tag remains challenging because surface functionalization is inherently stochastic. Here, we present a batch‐scale strategy to produce predominantly singly tagged SWCNTs by leveraging the stochastic adsorption of single‐stranded DNA (ssDNA). Specifically, SWCNTs are dispersed using a mixture of unmodified ssDNA (um‐ssDNA) and a minor fraction of modified ssDNA (m‐ssDNA) carrying an affinity handle. We developed a probabilistic ssDNA–SWCNT binding model that predicts the distribution of m‐ssDNA per nanotube as a function of the input minor‐strand fraction p = m‐ssDNA/total ssDNA, enabling selection of conditions that maximize single‐tag purity. Using magnetic‐bead capture via a biotin affinity interaction and subsequent release, we isolate SWCNTs with 97.6% predicted single‐tag purity at 2% recovery. Single‐molecule fluorescence imaging further supports predominantly single‐label occupancy under the model‐selected conditions. Thus, this approach provides a general route to SWCNTs bearing a single molecular handle for downstream conjugation and assembly, supporting diverse future applications in SWCNT‐based nanotechnologies.