Highly sensitive plasmonic sensing based on a topological insulator nanoparticle

Topological insulators (TIs) are a new type of Dirac material that possess unique electrical and optical properties, enabling the generation of surface plasmons over an extensive spectral range with promising applications in functional devices. Herein, we fabricated antimony telluride (Sb₂Te₃) TI nanoparticles by using magnetron sputtering and focused ion beam (FIB) lithography techniques, and experimentally demonstrated high-performance refractive index nanosensing. We find that the Sb₂Te₃ TI nanoparticles can support the excitation of localized surface plasmon resonance (LSPR), which depends on the dimensions of the TI nanoparticle. TI-based LSPR can contribute to the nanoscale sensing of the surrounding refractive index with a high sensitivity of 443 nm RIU^-1, which is comparable to that of plasmonic sensors based on metallic nanoparticles. The experimental results are in excellent agreement with finite-difference time-domain (FDTD) numerical simulations. This work will pave a new way to explore TI optical properties and applications in nanophotonic devices, especially plasmonic nanosensors.