Precise regulation of surface plasmonic hotspots in an Au split nanoring coupled system

Abstract

The signal enhancement in plasmon-enhanced spectroscopy is primarily contributed by hotspots generated through the surface plasmon resonance effect. Precise control of hotspot positions within nanostructures is of great significance in surface-enhanced Raman spectroscopy (SERS) and high spatial resolution imaging. However, predicting the positions of hotspots is challenging due to the small nanogaps and complex plasmonic interactions. In this study, we theoretically investigate the localized surface plasmonic properties of split ring nanostructure. The effects of variations in the inner radius, gap distance and thickness of the split ring on the hotspot distribution at the nanogaps are systematically analyzed using a three-dimensional finite element method. The results demonstrate that precise control over the positions and quantities of hotspots can be achieved by choosing the excitation wavelength and the gap size of the split rings. The calculated maximum Raman enhancement obtained at the hotspots can reach nine orders of magnitude. Our findings not only contribute to a deeper understanding of the SERS enhancement mechanism, but also provide theoretical insights for further development of surface-enhanced fluorescence, plasmonic sensors, and super-resolution imaging in the field of interface spectroscopy.