(111)-facet dominant ultrafine nanoporous silver as SERS substrates with high sensitivities and ultrahigh detection limits

Highlights: • (1 1 1)-facet dominant nanoporous Ag prefers to form at applied potential of −0.5 V. • Many Ag bumps (d ≈ 5 nm) distribute on Ag ligaments. • ONP-Ag@-0.5V has S_BET of 13 m² g⁻¹ and d_pore of 16 nm. • Advantages listed above and embeded ZnO synergetically enhance SERS of ONP-Ag@-0.5V. • ONP-Ag@-0.5V has a SERS EF of 5.54 × 10¹⁰ and LOD of 4.8 × 10⁻¹⁴ M for R6G. (1 1 1)-facet dominant nanoporous Ag (ONP-Ag@-0.5V) has been fabricated by electrochemical dealloying of Ag₂₀Zn₈₀ precursor alloys composed of ε-AgZn₃ single phase in 0.5 M KOH solution at the applied potential of −0.5 V. The ONP-Ag@-0.5V has a finer nanoporous structure with an average pore size of 16 nm and the specific surface area of 13.0 m² g⁻¹. The Surface-enhanced Raman scattering (SERS) activity of the ONP-Ag@-0.5V for Rhodamine 6G (R6G) Raman probe is evaluated to be with a SERS enhancement factor of 2.53 × 10¹⁰ and limit of SERS detection of 4.8 × 10⁻¹⁴ M. The superior SERS activities mainly arise from the local electromagnetic enhancement effects of ultrafine (1 1 1)-facet dominant nanoporous structure and the narrow ligaments, the edge effects from co-distribution of Ag bumps, the plasmonic effect of the embedded ZnO, as well as the chemical enhancement of (1 1 1)-facet adsorption of more R6G molecules.