Correlation of surface potential and SERS-activity of Ag particles formed by electroless deposition on Si-based substrate

We propose an approach to identify points on a timeline of Ag wet electroless deposition on macroporous silicon (macro-PS) that correspond to formation of Ag particles possessing prominent surface-enhanced Raman scattering (SERS) activity. This approach is measuring a surface potential of macro-PS, which sharply decreases at the moment of nearly complete saturating the Si skeleton surface with Ag particles of diameter below 60 nm favorable for an intensive surface plasmon resonance. The most intensive SERS-spectra of 5,5′-dithio-bis-[2-nitrobenzoic acid] (DTNB) were collected on macro-PS covered with Ag particles for 20 min. Considering breaking S–S bonds of DTNB in presence of Ag, which leads to chemisorption of monomolecular TNB layer on the surface of Ag structures, we claim 2 × 10−9 M TNB detection limit. Lower concentration at 10−10 M resulted in absence of SERS-spectra in some spots showing that the analyte was adsorbed unevenly. The analytical enhancement factor was calculated as ∼0.7 × 107.