Effective Plasmonic Coupling and Propagation Facilitates Ultrasensitive and Remote Sensing Using Surface Enhanced Raman Spectroscopy

Surface-enhanced Raman spectroscopy (SERS) is a sensitive technique for the detection of analytes through light scattering that is enhanced by chemical and electromagnetic effects through interactions on surfaces, particularly in nano-gaps. Herein we show that dissolved oxygen is the strongest attenuator of the SERS response in aqueous solution and its removal by chemical means can lower the detection limit by 10⁹–10¹⁰ times, to achieve unprecedented sensitivity, i.e., detection of a single molecule in ~300 µL of sample solution. It also enables remote detection of the analyte outside of the field of view of the incident laser beam, e.g., over a distance of 1 m, which we propose is due to the coupling of the plasmonic field within and between nanoparticle aggregates, allowing for signal transmission throughout the sample volume.