Probing the Location of 3D Hot Spots in Gold Nanoparticle Films Using Surface-Enhanced Raman Spectroscopy.

Plasmonic "hot spots" play a key role in surface-enhanced Raman scattering (SERS) enabling its ultrahigh surface sensitivity. Thus, precise prediction and control of the location of hot spots in surface nanostructures is of great importance. However, it is difficult to predict the exact location of hot spots due to complex plasmon competition and synergistic effects in three-dimensional (3D) multiparticle surface configurations. In this work, three types of Au@probe@SiO2 core-shell nanoparticles were prepared and a 3D hot spots matrix was assembled via a consecutive layer on layer deposition method. Combined with SERS, distinct probe molecules were integrated into different layers of the 3D multiparticle nanostructure allowing for the hot spots to be precisely located. Importantly, the hot spots could be controlled and relocated by applying different excitation wavelengths, which was verified by simulations and experimental results. This work proposes a new insight and provides a platform for precisely probing and controlling chemical reactions, which has profound implications in both surface analysis and surface plasmonics.