Dual wavelength sensing based on interacting gold nanodisk trimers

Area of Science:

• Nanotechnology
• Plasmonics
• Optical Materials

Background:

• Surface plasmon resonance (SPR) is a phenomenon sensitive to the local dielectric environment.
• Gold nanostructures are widely explored for their unique optical properties and sensing capabilities.
• Controlling the geometry of nanostructures is crucial for tuning their plasmonic responses.

Purpose of the Study:

• To fabricate and characterize periodic arrays of gold disk trimers with high precision.
• To investigate the surface plasmon properties of these nanostructures as a function of their dimensions.
• To evaluate the sensing potential of gold disk trimers for chemical detection.

Main Methods:

• Electron beam lithography was employed for the precise fabrication of gold disk trimers.
• Optical extinction spectroscopy was used to study the surface plasmon resonances.
• Finite-difference time-domain (FDTD) simulations were performed to analyze optical extinction spectra and electric near-field intensities.
• Sensing properties were investigated by coating the nanostructures with various media.

Main Results:

• Fabrication achieved disk diameters as small as 96 nm and gaps as narrow as 10 nm with high reproducibility.
• Intense visible and infrared surface plasmon resonances were observed in the disk trimers.
• Resonances were attributed to both individual trimer responses and collective excitations due to inter-trimer electromagnetic interactions.
• The nanostructures exhibited promising sensing capabilities when coated with different materials.

Conclusions:

• Gold disk trimers can be fabricated with exceptional control over size and spacing.
• The observed surface plasmon resonances are tunable by adjusting structural parameters.
• Gold disk trimers show potential for application in dual-wavelength chemical sensing.