Spatial-Tunable Au Nanoparticle Functionalized Si Nanorods Arrays for Surface Enhanced Raman Spectroscopy

Area of Science:

• Nanotechnology
• Spectroscopy
• Materials Science

Background:

• Surface-enhanced Raman spectroscopy (SERS) is a powerful technique for molecular detection.
• Optimizing the spatial distribution of plasmonic nanoparticles on nanostructured substrates is crucial for enhancing SERS performance.
• Silicon nanorods (SiNRs) offer a versatile platform for fabricating SERS substrates.

Purpose of the Study:

• To fabricate and investigate hexagonal-packed Si nanorod arrays conjugated with gold nanoparticles (AuNPs) in various spatial arrangements.
• To evaluate the impact of different AuNP functionalization positions (bottom, top, sides) on SiNRs for SERS applications.
• To explore the potential of these tunable substrates for sensitive and reproducible molecular detection.

Main Methods:

• Fabrication of hexagonal-packed Si nanorod arrays.
• Functionalization of SiNRs with Au nanoparticles at the bottom (B-SiNRs@AuNPs), top (T-SiNRs@AuNPs), and sides (S-SiNRs@AuNPs).
• Characterization of SERS performance using R6G molecules.
• Finite-difference time-domain (FDTD) simulations to understand light-matter interactions.

Main Results:

• SiNRs conjugated with AuNPs on the sides (S-SiNRs@AuNPs) demonstrated high reproducibility in detecting R6G molecules.
• AuNPs on the top of SiNRs (T-SiNRs@AuNPs) exhibited the strongest Raman signal enhancement.
• The S-SiNRs@AuNPs substrate showed the highest spatial uniformity of SERS enhancement.
• FDTD simulations confirmed light confinement within SiNR arrays, leading to zero-gap enhancement with AuNPs.

Conclusions:

• Spatially controlling AuNP distribution on SiNR arrays significantly impacts SERS performance.
• The developed SiNRs@AuNPs substrate offers tunable sensitivity and excellent reproducibility for molecular detection.
• This work provides a promising platform for advanced SERS applications in chemical and biological sensing.