A dual strategy integrating “geometric design” and “diffusion engineering” for tuning SERS performance of rose-thorn-shaped nanoporous Ag

Diffusion couples of Ag/Al stacking foils with layered structures as good precursors. • Rose-thorn-shaped nanoporous Ag inherits Ag 2 Al phase. • Flexibility of SERS substrates is from unreacted Ag layer and nanoporous Ag layer. • SERS limit of detection of 1 × 10 −16  mol·L −1 . • High Raman scattering is arisen from surface rose-thorn-shaped nanoporous Ag. Establishing highly accurate and sensitive surface enhanced Raman scattering (SERS) substrate is of critical importance for trace-level detection of probe molecules. An ultrasensitive and flexible Ag SERS substrate for rhodamine 6G (R6G) and crystal violet (CV) is rationally designed and successfully fabricated via the way of “geometric coupling design of thermal-diffusion induced phase growth” and “nanoporous structure inheritance”. The formation of rose-thorn-shaped nanoporous Ag and hierarchical nanoporous architecture with pore size distribution is governed by microstructural inheritance from tip diffusion growth Ag 2 Al intermetallic phase of Ag/Al thermal diffusion couples. Consequently, SERS substrate achieves ultralow detection limits of 10 −16  mol·L −1 for both R6G and CV, outperforming previously reported nanoporous Ag-based SERS substrates. The excellent mechanical flexibility originates from the synergistic integration of undiffused Ag layer as a structural backbone and nanoporous top-layer that undergoes controlled deformation for effective energy absorption. There rose-thorn-shaped nanoporous Ag collectively generate pronounced localized electromagnetic hot spots and stronger localized surface plasmon resonance, one of them yielding a local enhancement factor of approximately 10 5 . The superior SERS performance arises from enhanced surface scattering from rose-thorn-shaped nanostructure and strong electromagnetic coupling within the ultra-narrow nanopores with average pore size of 11 nm.