Self-Assembled Rhodium Nanoantennas for Single-Protein UV SERS.

Surface-enhanced Raman scattering (SERS) provides critical insights into analyte structure, dynamic processes, and intermolecular interactions at the single-molecule level. By exploiting the hotspot formed in the vicinity of plasmonic structures, SERS has become an established tool for fundamental biological research, particularly for early-stage disease diagnostics. DNA Origami, with its high addressability, enables both the assembly of plasmonic nanostructures with nanometric accuracy, and the deterministic placement of a single analyte molecule precisely at the hotspot. Most DNA Origami based nanoantennas rely on gold or silver nanoparticles (NPs), whose plasmonic resonances are confined to the visible spectrum, hindering the exploitation of the strong biomolecules' absorbance in the UV range. To benefit from the supplementary Raman signal enhancement in the UV, we extended the operational range of SERS with a deterministic strategy for self-assembling (UV)-plasmonic dimer antennas using rhodium nanocubes. Herein, we leverage this tailored architecture to systematically investigate its performance for single-molecule UV-SERS and demonstrate how biofabricated Rh-dimers can be used to detect the characteristic SERS signal of a single streptavidin molecule linked at the dimer's gap. Our results are validated by polarization-dependent measurements on a single dimer, which show the expected modulation of the SERS signal with dimer orientation only for DNA origami structures hosting a protein in the hotspot. This work establishes a highly sensitive and polarization-tunable UV-SERS platform and lays a solid foundation for label-free optical investigation and bio-spectroscopy of individual biomolecules in the UV spectral range.