Optical field and chemical environment near the surface modified gold nanoparticle assembly revealed by two-photon induced photoluminescence and surface enhanced raman scattering

Gold nanoparticle assemblies significantly enhance optical fields and have been applied for nano-optical devices, biosensing, and chemical reactions. The optical properties of the assembly are, however, less controllable once the assemblies are fabricated on a solid substrate. An assembly prepared at the water-organic solvent interface overcomes this restriction and provides flexible photochemical reaction fields. Additionally, the physical and chemical properties of the assembly can be controlled by modification of the nanoparticle surface. In this study, we investigated the optical properties of the assembly using two-photon-induced photoluminescence and surface-enhanced Raman scattering, and demonstrated that the optical field enhancement and chemical environment near the gold nanoparticle assembly can be finely controlled by surface-modification of the gold nanoparticles.