Shaped femtosecond laser-regulated deposition sites of galvanic replacement for simple preparation of large-area controllable noble metal nanoparticles

Controllable deposition sites in galvanic replacement (GR) are crucial for the application performance of noble metal nanoparticles (NMNPs). However, the simplicity and effectiveness of the existing research methods for controlling GR deposition sites are still needed to be improved. Herein, a novel method is proposed to simply and effectively control the deposition sites of NMNPs (Au and Pt) in the GR reaction by shaped femtosecond laser surface pre-modification. First, the localized free electron density of silicon is regulated by spatially shaped femtosecond laser to efficiently produce large-area uniform periodic amorphous transformation, which periodically changes the chemical reducibility of silicon. Second, this difference in chemical reducibility guides the subsequent GR reaction to produce large-area NMNPs with controllable deposition sites. By controlling the distribution and density of particles, these controllable NMNPs exhibit a superior SERS performance to the particles prepared by GR reaction alone: the maximum EF is 8.46 × 10⁷ with high signal uniformity (RSD < 9.7%) and superior chemical stability (4.8% intensity deviation after 2 months in the air), which indicated the advantages of NMNPs with controllable deposition sites. This study provides a facile method to control the GR deposition sites and a new idea for Raman-enhanced substrate preparation.