Dielectric function modelling and sensitivity forecast for Au-Ag alloy nanostructures.

Area of Science:

• Nanotechnology
• Materials Science
• Optics

Background:

• Plasmonic nanostructures offer high spectral sensitivity for sensing applications.
• Refractive index sensitivity (RI sensitivity) is crucial for sensor performance.
• Core-shell nanostructures, like gold nanobipyramids (AuBP) with Au-Ag alloy shells, are being explored for enhanced sensing capabilities.

Purpose of the Study:

• To investigate the refractive index sensitivity (RI sensitivity) and figure of merit (FOM) of Au-Ag alloy shelled AuBP nanostructures.
• To understand the influence of nanostructure geometry and composition on localized surface plasmon resonance (LSPR) properties.
• To validate theoretical models with experimental results for predicting nanostructure sensitivity.

Main Methods:

• Utilized the Drude-critical points model (DCPM) to calculate frequency-dependent dielectric properties of Au-Ag alloys.
• Employed finite difference time domain (FDTD) simulations to model LSPR optical spectra based on DCPM data.
• Synthesized Au-Ag alloy nanoshells on AuBPs using wet-chemical methods for experimental validation.

Main Results:

• RI sensitivity is dependent on bulk plasma wavelength, alloy dielectric properties, and geometrical parameters.
• FDTD simulations accurately predicted RI sensitivities, aligning well with experimental measurements.
• The combined DCPM and FDTD approach provides a reliable method for forecasting the sensitivity of alloyed nanostructures.

Conclusions:

• The study demonstrates the effectiveness of combining DCPM and FDTD simulations for predicting the optical properties of Au-Ag alloy nanostructures.
• Experimental validation confirms the accuracy and feasibility of the theoretical modeling approach.
• This work provides a pathway for designing and optimizing plasmonic nanostructures for advanced chemical and biological sensing.