[17a-A402-1~11] 3.12 Nanoscale optical science and near-field optics

▼ [17a-A402-9] LSPR Tuning of Ag@SiO₂ Core-Shell Nanosphere Trimer Configurations

〇(D)ANITHARAJ NAGARAJAN^1,2, ARUNA PRIYA PANCHANATHAN², PANDIAN CHELLIAH³, HIROAKI SATOH⁴, HIROSHI INOKAWA⁴ (1.GSST, Shizuoka Univ., 2.SRM Inst. of Sci&Tec, 3.R.K.M.Vivekananda, 4.RIE, Shizuoka Univ.)

Keywords:Trimer, Core-shell, LSPR

Electromagnetic illumination can excite the collective oscillations of free electrons around the nanoparticles which arises to an optical phenomenon called LSPR (localized surface plasmon resonance). This LSPR effect enhances and localizes the electromagnetic field in the near vicinity of nanoantenna. Metal nanoparticle clusters with core-shell structures are promising structures providing highly localized e-field within the core-shell crevices and at the junction between the nanoparticles called “hot-spots” and can able to detect a small amount of analyte in spectroscopic sensing techniques such as surface enhanced Raman spectroscopy (SERS). In this work the evolution of LSPR properties of core-shell (Ag@SiO₂) nanosphere trimer of gap size, 2nm is analyzed as the symmetric configuration is transformed from linear to equilateral triangle by using FDTD simulation tool, MEEP. This is done by varying the vertex angle of the triangle. The key factor in sensing based on LSPR is to excite the LSPR modes of trimer nanospheres to yield a high e-field enhancement. The LSPR peak of trimer core-shell with kinked triangle configuration exhibits an enhancement of value, 547 which is nearly 8 times greater than the silver nanosphere. This is due to the arise of hot-spots in the nanogaps and the excitation of plasmonic modes of its kinked triangle configuration. The effect of the polarization dependence of trimer on E-field intensity has also been analyzed. The equilateral triangle and kinked triangle configurations do not highly depend on the polarization where equilateral shows an enhancement value of 338 and 208 for parallel and perpendicular polarization, respectively, and same trend is observed in the case of kinked triangle as well. However, the E-field intensity of equilateral triangle configuration exhibits a strong polarization dependence. For parallel polarization the enhancement value is 470 and for the perpendicular polarization the value is decreased to 100. Thus the geometry and polarization dependence of the E-field intensity of trimer configurations are investigated and the highest E-field intensity of kinked triangle configuration is a good choice for building it as an array for the application such as SERS.