Pattern Recognition Directed Assembly of Plasmonic Gap Nanostructures for Single-Molecule SERS.

Gold nanocubes (AuNCs) with tunable localized surface plasmon resonance properties are good candidates for plasmonic gap nanostructures (PGNs) with hot spots (areas with intense electric field localization). Nevertheless, it remains challenging to create shape-controllable nanogaps between AuNCs. Herein, we report a DNA origami directed pattern recognition strategy to assemble AuNCs into PGNs. By tuning the position and number of capture strands on the DNA origami template, different geometrical configurations of PGNs with nanometer-precise and shape-controllable gaps are created. The localized field enhancement in these gaps can generate hot spots that are in accordance with finite difference time domain simulations. Benefiting from the single Raman probe molecule precisely anchored at these nanogaps, the dramatic enhanced electromagnetic fields localized in hot spots arouse stronger single-molecule SERS (SM-SERS) signals. This method can be utilized in the design of ultrahigh-sensitivity photonic devices with tailored optical properties and SERS-based applications.