Abstract
In this study, the effect of the plasmon hybridization mechanism on the performance and refractive index (RI) sensitivity of nanoshell, nanocage and nanoframe structures is investigated using the finite-difference time-domain simulation. To create nanocage structure, we textured the cubic nanoshell surfaces and examined the impact of its key parameters (such as array of cavities, size of cavities and wall thickness) on the nanocage's RI-sensitivity. Synthesis of the designed nanocages is a challenging process in practice, but here the goal is to understand the physics lied behind it and try to answer the question “Why nanoframes are more sensitive than nanocages?”. Our obtained results show that the RI-sensitivity of nanocage structures increases continuously by decreasing the array of cavities. Transforming the nanocage to the nanoframe structure by reducing the array of cavities to a single cavity significantly increases the RI-sensitivity of the nanostructure. This phenomenon can be related to the simultaneous presence of symmetric and asymmetric plasmon oscillations in the nanocage structure and low restoring force of nanoframe compared to nanocage. As the optimized case shows, the proposed single nanoframe with aspect ratio (wall length/wall thickness) of 12.5 shows RI-sensitivity of 1460 nm/RIU, the sensitivity of which is ~ 5.5 times more than its solid counterpart.
Highlights
In this study, the effect of the plasmon hybridization mechanism on the performance and refractive index (RI) sensitivity of nanoshell, nanocage and nanoframe structures is investigated using the finitedifference time-domain simulation
localized surface plasmon resonances (LSPRs) is the result of collective oscillations of conduction electrons on the surface of metallic nanoparticles which are induced by electromagnetic fields of the incident light[10]
We have shown the effect of plasmon hybridization mechanism on the LSPR properties and RIsensitivity of several single metallic nanostructures: SiO2@Au core–shell nanocube, Au nanocage, and nanoframe characterized by FDTD simulation
Summary
The effect of the plasmon hybridization mechanism on the performance and refractive index (RI) sensitivity of nanoshell, nanocage and nanoframe structures is investigated using the finitedifference time-domain simulation. A red- or blue-shift phenomenon may occur in LSPR wavelength when the refractive index of the local environment is changed This feature of metallic nanoparticles allows us to design optical nanosensors for the detection of the chemical changes such as protein interactions14, antibodies[15] in molecular dimensions for applications involved in biomarker for Alzheimer’s d isease[16] and so on. The influence of nanoshell thickness on the plasmonic hybridization mechanism is studied by H alas[19] Her results show that the energy gap between two modes of hybrid surface plasmons (symmetric and asymmetric modes) increases as the nanoshell thickness decreases and frequency shift (with respect to solid nanoparticle) is larger for thinner nanoshells. The spherical nanoshells are the simplest structures in complex hollow structures which hybridization model could describe
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