Fig. 1. Specific experimental scheme of nickel foam coated silver substrate

Fig. 2. Nickel foam coated silver substrate. (a1) Optical photos of nickel foam coated silver substrate; (a2) SEM image of pure nickel foam substrate; (b1)-(h1), (b2)-(h2) SEM images of nickel foam substrates coupled silver nanostructures

Fig. 3. Simulation of electromagnetic field. (a) Simulation model of silver nanoparticles; (b)-(d) electric field distributions of substrates at y-z plane

Fig. 4. Raman spectra and enhancement factor of R6G molecules for different conditions. (a)(b) Raman spectra and enhancement factor of R6G molecules on substrates with different silver nitrate concentration; (c)(d) Raman spectra and enhancement factor of R6G molecules on substrates with different replacement time

Fig. 5. Test areas and Raman spectra of sample,and RSD of substrate. (a) Test areas and Raman spectra of sample; (b) RSD of substrate

Fig. 6. Raman spectra of R6G. (a) Raman spectra of R6G with concentration of 10^-11 mol·L^-1; (b) Raman spectra of R6G with concentration of 10^-12 mol·L^-1