Dielectric domain distribution on Au nanoparticles revealed by localized surface plasmon resonance

Localized surface plasmon resonance (LSPR) of metal nanoparticles has been proven to be sensitive to their dielectric environment and molecular binding, but less is known about the capability of LSPR towards differentiating homogeneous versus segregated molecular distribution on the nanoparticle surface. Using silica on Au nanospheres to mimic the dielectric change caused by molecules on the nanosphere surface, we have discovered that the LSPR of Au nanospheres is sensitive to the distribution of dielectric domains. We grew discrete silica domains or a continuous shell on the Au nanosphere surface and observed that the discrete domains of silica induced very little shift in the LSPR while the uniform shell caused a drastic shift. Theoretical modeling further confirmed that even when the volume of the silica was kept the same, the discrete domains had much smaller impact on the LSPR of Au nanospheres than the continuous shell. Moreover, for an anisotropic Au nanorod, the simulation results show that the LSPR is more sensitive to the dielectric change at the ends (hot spot) than the sides. The study suggests that the LSPR of metal nanoparticles can be conveniently used as an indirect method to reveal the dielectric distribution on the nanoparticles.