Figure 4From: Surface-enhanced Raman spectra of medicines with large-scale self-assembled silver nanoparticle films based on the modified coffee ring effectScanning electron microscope images of silver nanoparticle film. Prepared with different concentrations of silver nanoparticle solution: (a) 1 mM, (b) 10 mM, (c) 50 mM, and (d) 0.1 M. The inset shows high-magnification SEM image of the film.Back to article page