Figure 6 SERS spectra of GNPs, GNPs in PBS, GNPs incubated with 9 mg/mL BSA and GNPs preincubated with 9 mg/mL BSA and resuspended in PBS: A) AuNP50, B) AuNP70 and C) AuNS.
To explain the observed SERS results, the electric field distribution around the AuNS was simulated via FEM calculation (Figure 7 A) . The electric field around tips has a dramatic enhancement compared to the region around the core so protein molecules, adsorbed onto the core would not have a significant SERS enhancement, though they do contribute to the redshift of the LSPR (Figure 7 B ). Spherical nanoparticles do not have areas with high curvature, which makes enhancement homogeneous on the surface and much weaker, compared to AuNS “hot-spots” enhancement (Supporting Information Figure S1 ).