DNA-assisted synthesis of Ortho-NanoDimer with sub-nanoscale controllable gap for SERS application.

Nanostructure with precisely controllable narrow gap width remains a great challenge, especially at the sub-nanoscale level. Here, a versatile strategy named as DNA-assisted synthesis of ortho-nanodimer (DaSON) is proposed to fabricate Ag (Au) nanodimers with a uniform gap width from nanometers to angstroms. In such a strategy, two nanoparticles are constrained by the equilibrium state of the DNA hybridization and electrostatic repulsion to form zipper-like ortho-nanostructures with an extremely uniform gap whose width can be finely adjusted at nanoscale or sub-nanoscale by changing the DNA sequence and the surface charge of nanoparticles. The inherent strong electromagnetic coupling in the uniform sub-nanometer gap can generates an unparalleled SERS enhancement together with an extraordinary reproducibility. Compared with conventional DNA-based nano-gap fabrication strategy, the DaSON strategy enhances the SERS intensity for more than two orders of magnitude with a detection limit of 100 aM for DNA, and significantly improves the reproducibility in both labeled and label-free SERS sensing applications. Moreover, the DaSON strategy holds wide applicability for arbitrary kinds of DNA-modifiable nanoparticles. Therefore, we believe that the DaSON strategy provides an innovative method for the synthesis of nanostructures with controllable nanogaps and has a promising future in multiple fields including nanotechnology, catalysis and photonics.