Department of Physics, University of Isfahan, P.O. Box 81746-7344, Isfahan, Iran.
Quantum Optics Research Group, University of Isfahan, Isfahan, Iran.
Sci Rep. 2021 Jan 22;11(1):2065. doi: 10.1038/s41598-021-81578-w.
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.
在这项研究中，我们使用时域有限差分法模拟研究了等离激元杂化机制对纳米壳、纳米笼和纳米框结构的性能和折射率（RI）灵敏度的影响。为了构建纳米笼结构，我们对立方纳米壳的表面进行了纹理处理，并研究了其关键参数（如腔阵列、腔的大小和壁厚度）对纳米笼 RI 灵敏度的影响。虽然在实际中合成设计的纳米笼是一个具有挑战性的过程，但这里的目标是理解其背后的物理原理，并尝试回答“为什么纳米框比纳米笼更灵敏？”这一问题。我们的研究结果表明，通过减小腔阵列，纳米笼结构的 RI 灵敏度会持续增加。通过将纳米笼结构转化为纳米框结构，并将腔阵列减小为单个腔，可以显著提高纳米结构的 RI 灵敏度。这种现象可以归因于纳米笼结构中同时存在对称和非对称等离子体振荡以及纳米框与纳米笼相比具有较低的恢复力。优化后的单纳米框的结构，其纵横比（壁长/壁厚）为 12.5，具有 1460nm/RIU 的 RI 灵敏度，其灵敏度比其实心对应物高约 5.5 倍。
