Simultaneous Electrochemical Formation of Porous Silicon and Noble NPs for Au Nucleation Sites in SERS Substrates

This study presents a one-step electrochemical etching strategy that enables the simultaneous formation of porous silicon (PSi) and in situ deposition of noble metal nanoparticles (NPs), which subsequently act as nucleation sites for gold growth to form bimetallic SERS substrates. Three metal precursors─K2PtCl4, HAuCl4, and K2PdCl4─were systematically compared to elucidate how precursor type affects PSi morphology, nanoparticle distribution, and subsequent gold deposition. SEM and EDS analyses revealed distinct deposition behaviors among the metals, leading to varied gold nucleation efficiencies and SERS enhancement levels. HAuCl4-treated substrates produced the highest absolute Raman intensity, while K2PtCl4-treated substrates exhibited lower intensity but superior spectral quality with minimal fluorescence background and sharper peaks. XRD and XPS confirmed successful gold deposition and precursor-dependent interfacial interactions, including the formation of Pt–Au bimetallic interfaces. Reusability tests demonstrated that the Pt-assisted substrates maintained stable performance over multiple cycles, confirming their structural robustness and practical feasibility. Overall, this work provides mechanistic insight into how noble metal interfaces govern SERS spectral characteristics and establishes a rational pathway for designing PSi-based SERS substrates emphasizing spectral precision, reproducibility, and reusability rather than mere sensitivity enhancement.