Gold Nanopyramids Assembled into High-Order Stacks Exhibit Increased SERS Response

Area of Science:

• Nanotechnology
• Plasmonics
• Spectroscopy

Background:

• Gold pyramidal nanoshells (nanopyramids) are promising for plasmonic applications.
• Controlling nanoparticle assembly is key to tailoring their optical properties.

Purpose of the Study:

• To investigate the assembly of gold nanopyramids into low- and high-order structures.
• To correlate assembly order with surface-enhanced Raman scattering (SERS) performance.

Main Methods:

• Controlled solvent evaporation and surface wettability to direct nanopyramid assembly.
• Dark field scattering spectroscopy to analyze optical properties of assembled structures.
• Surface-enhanced Raman scattering (SERS) measurements using methylene blue.
• Finite-difference time-domain (FDTD) modeling to simulate electromagnetic field distributions.

Main Results:

• Nanopyramid assembly into low- and high-order structures was achieved by controlling evaporation rate and wettability.
• Short wavelength resonances blue-shifted upon assembly, with larger shifts in high-order structures.
• High-order nanopyramid assemblies exhibited significantly enhanced SERS response compared to low-order assemblies.
• FDTD modeling confirmed maximum electromagnetic field intensities localized between adjacent nanopyramid faces.

Conclusions:

• The local spatial arrangement of nanoparticles in assembled clusters is a critical design parameter for SERS sensors.
• Optimizing nanopyramid assembly can enhance electromagnetic field localization and SERS signal intensity.
• This work provides insights into designing efficient nanoparticle-based SERS sensors through controlled assembly.