DNA-Surfactant Exchange and Quantifying Interactions of Pure (n,m) Single-Enantiomer SWCNTs Towards Biohybrid Self-Assembly

Self-assembled biohybrid nanostructures made from single-wall carbon nanotubes (SWCNTs) and DNA are a promising model system for studying fundamental photo physics phenomena, and have significant potential as building blocks for applications such as biosensing and photovoltaics devices. Precise control of SWCNT bandgap and length in these biohybrid assemblies is highly desirable, but scalable production of such samples often benefits from processing in aqueous polymer and surfactant solutions that are then typically incompatible with DNA-directed assembly. DNA exchange is a promising route for replacing surfactants with self-assembling DNA sequences after these purification steps. Unfortunately, despite advances, DNA exchange remains a challenging technique with limitations due to uncontrolled aggregation and low yields. In this work we focus on improving the process for several well-defined SWCNT samples that are both single chirality and single enantiomer refined through aqueous two-phase separation as well as length sorted to a narrow distribution. With these, we demonstrate improvements in DNA exchange in both yield and control of the aggregation state by modifying DNA exchange processing parameters. We also show that the exchanged DNA-wrapped SWCNTs can be linked together by the addition of a complementary DNA bridge to form self-assembled biohybrid nanostructures for energy transfer studies. We use analytical ultracentrifugation and absorbance and photoluminescence spectroscopies to measure and quantify changes in as these biohybrid structures self-assemble. These developments pave the way for high yield assembly of precise biohybrid nanostructures for energy transfer studies and open potential applications in photovoltaics and biosensing.