Ultraviolet Resonant Nanogap Antennas with Rhodium Nanocube Dimers for Enhancing Protein Intrinsic Autofluorescence

Plasmonic optical nanoantennas have revolutionized the control of light-matter interactions at the nanoscale. However, until now, their exploration has been largely restricted to the visible and near-infrared regions, overlooking the immense potential of the ultraviolet range, which boasts the strongest absorption for most molecules. In a recent ACS Nano article, entitled “Ultraviolet Resonant Nanogap Antennas with Rhodium Nanocube Dimers for Enhancing Protein Intrinsic Autofluorescence” we overcome the materials and technical limitations of UV nanophotonics and report the first experimental realization of UV resonant nanogap antennas.

Our design relies on the directed self-assembly of rhodium nanocubes into dimer nanogap antenna. We pioneer the use of rhodium as a robust alternative to aluminum, offering enhanced stability in aqueous environments and ensuring reliable UV performance. Our results demonstrate the pivotal role played by the nanogap and stand in excellent agreement with numerical simulations.

We apply the UV nanoantennas to enhance the UV autofluorescence from single label-free proteins, and achieve unprecedented enhancement factors up to 120 fold together with zeptoliter detection volumes. By enhancing the protein autofluorescence signal by up to two orders of magnitude, our results unlock powerful perspectives for local measurements of concentration, mobility, brightness, and stoichiometry of label-free proteins, circumventing the need for external fluorescent labels.

This work broadens the scope of applicability for plasmonic nanoantennas into the deep UV range, unlocking novel avenues to take maximum advantage of the strong molecular response in the UV regime.

Open access on ACS Nano website. Also available through ArXiv 2309.04152. Enjoy!