Fig. 1. Preparation process of gold-copper bimetal SERS substrate

Fig. 2. Morphology and composition of nanoporous copper

Fig. 3. SERS performance of Au@NPC substrate to 4-mpy in chlorauric acid plating solution with different concentration and reaction time and SERS performance stability

Fig. 4. Variation of the morphology and composition of Au@NPC with gold planting time

Fig. 5. SERS variation with storage time