Ultrahigh sensitive refractive index nanosensors based on nanoshells, nanocages and nanoframes: effects of plasmon hybridization and restoring force

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.

High-sensitivity long-range surface plasmon resonance sensing assisted by gold nanoring cavity arrays and nanocavity coupling

“…Meanwhile, this symmetric oscillation of Mode III not only couples with the external optical fields, but also shows greater RI sensitivity compared with asymmetric modes. 34,35 Thus, the wavelength shift at Mode III was more prominent than those of the cSPR, pSPR substrate and the other four conventional modes of the LRSPR substrate. Meanwhile, the E z -field distributions were inspected to help elucidate the nature of the evanescent filed.…”

A dual functional asymmetric plasmonic silver nanostructure for temperature and magnetic field sensing

“…The resonant peaks redshifted from the near to mid-IR regions due to the reduced restoring force at ultra-small nano gaps. 40 These pronounced wavelength shifts resulted from the increase in Δ (%) or more certainly from the reduction in channel width ( W CR ), enabling an enhancement in the sensing function of the system. Here, the sensing performance was tailored by means of structural asymmetry, capitalizing on the independent resonant modes arising from non-uniform ring-disc coupling at different channel sizes.…”

High-Sensitive Detection and Quantitative Analysis of Thyroid-Stimulating Hormone Using Gold-Nanoshell-Based Lateral Flow Immunoassay Device

“…RIS is defined as the ratio of LSPR wavelength shift to the variation of the refractive index of the surrounding medium [56]. It has been reported that the RIS of gold nanoshells is in the range of 1460-1490 nm/RIU, whereas the RIS of gold nanoparticles is 44 nm/RIU [57,58]. This shows that RIS of gold nanoshells is 33 times higher than gold nanoparticles, which indicates that gold nanoshells are more suitable for plasmonic-based applications compared to gold nanoparticles.…”