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 ).