In-pore growth of gold nanoparticles in porous silicon films: Pore-architecture-dependent plasmonic and SERS properties

Three-dimensional porous silicon provides a scaffold for plasmonic nanocomposites, in which pore architecture influences nanoparticle growth, spatial distribution, and optical response. We demonstrate ultrasound-assisted in situ formation of gold nanoparticles (AuNPs) in porous silicon films with pore dimensions of approximately 5–35 nm. Medium- and large-pore architectures enabled AuNP formation throughout the porous layers, whereas AuNPs in the narrow-pore structure were predominantly localized near the surface. The resulting AuNP distribution produced changes in Fabry-Pérot interference, diffuse reflectance, and surface-enhanced Raman scattering (SERS). Substrates with depth-distributed AuNPs exhibited stronger and more reproducible SERS signals, with the medium-pore structure (~20 nm) showing the lowest calculated R6G detection limit (3.5 × 10 −9 M). Finite-element electromagnetic simulations revealed pore-geometry-dependent plasmonic modes and localized field enhancement near the Au-Si interface. These findings identify three-dimensional pore architecture as an important design parameter for controlling AuNP distribution, optical response, and SERS performance in porous silicon composites.