Study on mode shifts of localized surface plasmon cavity in Ag nanowire tetramer

Abstract

The interaction between noble metal nanowires can induce the local surface plasmonic resonance effect, thereby enhancing the distribution of electric field in the nanostructures, which is of very important significance in improving the fluorescence characteristics and enhancing the sensitivity of sensors. In this study, we design several types of tetramers based on precious metals Ag nanostructures, including cylindrical and prismatic Ag tetramers, and by changing the arrangement and the rotation angle of prism nanowires, we simulate the rotation-angle dependent electric field distribution and electric field intensity of <i>X</i> component , and also discuss the physical mechanism of the relationship between the resonant peak position of absorption spectrum and the change of mode volume. The results show that in the Ag nanowires tetramer structure, the electric field in the cylindrical structure is not enhanced obviously, but the electric field in the prismatic structure is greatly enhanced, and an electric dipole resonance mode is produced in the gap between tetramers. The polarization of plasma resonant cavity revels that the morphology plays a decisive role in generating the hot spots, After changing both the combination mode of tetramer nanowires and the rotation angle of the four-prism, the local surface exciton resonance of the unrotated asymmetric tetramer structure is most ideal and has resonance intensity higher than the that of symmetrical four-prism structure. Therefore, our results provide a structural model and theoretical parameters for the enhancement of electric field intensity by local surface plasmon resonance effect.