Self-Aligning Nanojunctions for Integrated Single-Molecule Circuits

Robust, high-yield integration of nanoscale materials such as graphene nanoribbons, nanoparticles, or single-molecules with conventional electronic circuits has proven to be challenging. This difficulty arises because the contacts to these nanomaterials must be precisely fabricated with angstrom-level resolution to make reliable connections, and at manufacturing scales this cannot be achieved with even the highest-resolution lithographic tools. Here we introduce an approach that circumvents this issue by precisely synthesizing nanometer-scale gaps between metallic electrodes using a self-aligning, solution-phase process, which allows facile integration with conventional electronic systems with yields approaching 50%. The electrode separation is controlled by covalently binding metallic single-walled carbon nanotube (mCNT) electrodes to individual DNA duplexes to synthesize hybrid mCNT-DNA-mCNT nanojunctions, where the gap is precisely matched to the DNA length. Upon integration, the resulting single-molecule circuits have electronic properties dominated by the DNA in the junction, have reproducible conductance values with low dispersion, and are stable and robust enough to be utilized as active, high-specificity electronic biosensors for dynamic single-molecule detection of specific oligonucleotides, such as those related to the SARS-CoV-2 genome. This scalable approach for high-yield integration of nanometer-scale materials will create new opportunities for manufacturing hybrid electronic systems for a wide range of applications.