Poly-Adenine-Engineered Gold Nanogaps for SERS Nanostructures

Surface-enhanced Raman scattering (SERS) effect, usually is associated with the highly confined electromagnetic field in plasmonic nanostructures, and has been widely investigated for molecular sensing and imaging applications. However, SERS substrates have confronted with poor reproducibility and inefficient nanometer-level structural control. By employing oligonucleotides, highly reproducible SERS substrates with uniform 1 nm nanogap could be constructed. In this work, we investigated the effect of oligonucleotides, especially the unmodified oligonucleotides, on the morphology of nanogaps. We found that the morphology of nanogap is dependent on the sequence, length, and surface-coating density of the unmodified oligonucleotide and speculate that the formation of nanogaps is dominated by stable self-assembled monolayers (SAMs) of unmodified oligonucleotides, which is supported by molecular dynamic simulation (MD) results. We further studied the morphologies of nanogaps, with oligonucleotide SAMs of different states and nanoseeds of different sizes and shapes. This work elucidated the relationships between the SAMs of unmodified oligonucleotides and the morphology of nanogaps, which will facilitate the design of reliable SERS nanostructures.