Large-Area Au-Nanoparticle-Functionalized Si Nanorod Arrays for Spatially Uniform Surface-Enhanced Raman Spectroscopy

Area of Science:

• Nanotechnology
• Spectroscopy
• Materials Science

Background:

• Surface-enhanced Raman spectroscopy (SERS) requires optimized substrates for ultrasensitive molecular detection.
• Silicon nanostructures offer a promising platform for SERS applications due to their tunable properties.

Purpose of the Study:

• To fabricate and characterize large-area hexagonal-packed silicon nanorod (SiNR) arrays functionalized with gold nanoparticles (AuNPs) for SERS.
• To investigate the SERS performance, including sensitivity, reproducibility, and uniformity, of the fabricated substrate.
• To demonstrate the potential of the SiNR-AuNP substrate for detecting large biomolecules, such as amyloid-β fibrils.

Main Methods:

• Fabrication of hexagonal-packed Si nanorod arrays.
• Functionalization of SiNR arrays with Au nanoparticles.
• Finite-difference time-domain (FDTD) simulations to analyze electric field distribution.
• SERS measurements using R6G molecules and amyloid-β fibrils.

Main Results:

• Achieved ultrasensitive molecular detection with high reproducibility and spatial uniformity.
• FDTD simulations revealed wide-range 3D electric fields and a long decay length (>130 nm) for the enhanced electric field.
• SERS system demonstrated an enhancement factor >10^7 for R6G molecules with low relative standard deviation (3.9-7.2%).
• Ultrasensitive Raman signals were obtained from amyloid-β fibrils at the single-fibril level.

Conclusions:

• The developed SiNR-AuNP substrate acts as a zero-gap system for ultrasensitive detection of large biomolecules.
• The substrate shows significant potential for the ultrasensitive detection of amyloid aggregates associated with Alzheimer's disease.
• SiNRs functionalized with AuNPs are excellent SERS substrates for chemical and biomedical applications.