Angular distribution of surface-enhanced Raman scattering from individual au nanoparticle aggregates.

Nano-optical antennas based on plasmonic metal particles are well-known for their ability to dramatically concentrate electromagnetic energy. However, not much attention has been devoted to the directionality properties of nanoantennas. Here, we report on the angular distribution of surface-enhanced Raman scattering (SERS) emitted by isolated aggregates of gold nanoparticles. We find that most of the radiation appears at angles exceeding the critical angle of the air-glass interface supporting the aggregates, and we demonstrate that angle-resolved imaging can be used as a fast and facile method for determination of the three-dimensional orientation and symmetry of the nanoantenna.