One-step machining of hierarchical micro-nano structures on Al-Mg alloy as superamphiphobic substrate for amplified SERS trace detection

Ultra-trace detection from polluted solution makes great contribution to environmental monitoring, food safety and medical analysis. However, its common difficulty arises in concentrating analytes on easily accessible substrate for highly amplified detection intensity. Herein, a superhydrophobic Al-Mg alloy surface focusing on droplet condensation and analyte detection is fabricated by an environment-friendly, efficient and low-cost machining process for surface enhanced Raman scattering (SERS) analyses. The micro-scale craters covered with nano-scale terrace-like structures have been prepared by one-step wire electrical discharge machining (WEDM). Meanwhile, wet abilities of hierarchical structures have been investigated after stearic acid modification. Results show that the as-prepared surface exhibits excellent repellent ability to water and oil drops. The resultant superamphiphobic surface also displays a 3-fold higher SERS intensity over hydrophilic Al-Mg alloy substrate. The corresponding SERS signals also show well signal reproducibility. This work sheds positive insights into fabricating accessible and efficient active substrates for SERS detection and extending potential applications of Al-Mg alloys in ultra-trace analysis in the future.