Fig. 1: DNA origami design and dimer synthesis.

a Gold nanorods are functionalised with different sequences of thiolated ss (single-strand) DNA (either T or R). Due to the differing labels, an individual nanorod can only bind to a designated binding site on the DNA origami support beam (either A8 or R’8) and nanorod dimers are formed. A docking site for the SERS analyte is precisely located between the nanorod tips, which form the plasmonic hotspot. b TEM image of GNR dimers assembled on the DNA origami support beam after sample purification. c Schematic of the SERS dark-field microscopy setup. Individual dimer nanoantennas are localized on a glass substrate by DFM. A 671 nm laser is coupled through the objective to perform SERS measurements on single nanoantennas, with analyte diffusing and binding into their hotspot gaps. A longpass (LP) filter is used to block the laser from entering the spectrometer.