Systematic investigation of the LSPR characteristics in plasmonic nanoarrays.

For plasmonic materials, it is crucial to modulate and couple their localized surface-plasmon resonances (LSPRs) frequencies with the incident laser to generate resonant electromagnetic fields. While the LSPR properties of colloidal plasmonic particles are well-established, the distinct morphology and LSPR behaviors of plasmonic nanoarrays fabricated by template-assisted evaporation remain insufficiently explored. This study systematically investigates the effects of particle diameter, deposition thickness, and surface roughness on the LSPR characteristics of nanoarrays. Furthermore, we demonstrate precise tuning of LSPRs through adjustments to the dielectric medium and composition in multilayer nanoparticles, as well as polarization dependence of anisotropic nanoparticles. Several critical, yet often overlooked, aspects were identified: (1) Physically deposited nanoparticles exhibit non-spherical morphologies, leading to LSPR characteristics that are distinct from those of idealized spheres. (2) Out-of-plane geometry strongly influences the LSPR response; notably, increasing the particle thickness can induce an LSPR blueshift, contrary to conventional expectations. (3) The dielectric environment plays a decisive role in governing the LSPRs of nanoarrays, including contributions from both the dielectric substrate and the surrounding medium. Moreover, we also demonstrate the capability of AAO-templated nanoarrays for plasmonic refractive index sensing, revealing a red shift of the LSPR peak with increasing refractive index and enhanced sensitivity for larger particle diameters. These findings provide insight into LSPR behaviors in nanoarrays and establish strategies for precise plasmonic tuning, deploying in LSPR sensing applications.