Plexcitonic Nanohybrids Based on Gold Nanourchins: The Role of the Capping Layer

Plexcitonic nanohybrids are plasmonic-excitonic novel materials whose peculiar properties are attracting considerable attention in photonics, solar cells, and sensing. These materials can be synthesized and characterized easily by assembling organic or inorganic dyes on plasmonic nanoparticles as support. However, the main factors controlling the assembly process and the occurrence of the plexcitonic coupling are still unclear. To fill this gap, in this work, we studied the plexciton coupling of 12 different dyes with a series of gold nanourchins with various coatings and sizes. Among 24 combinations tested, we observed the formation of plexcitonic hybrids only in five cases. Most of them had cyanine J-aggregates as excitonic counterparts. Stronger plexcitonic couplings were obtained when nanourchins were coated with an exchangeable citrate capping layer rather than a strong ionic thiols capping layer. We propose that the presence of a strongly bound capping layer, as in this latter ca...