Light absorption and plasmon-exciton interaction in three-layer nanorods with a gold core and outer shell composed of molecular J- and H-aggregates of dyes

Optical properties of hybrid rod-like nanoparticles, consisting of a gold core, an intermediate passive organic layer (spacer) and outer layer of ordered molecular cyanine dye aggregates, are experimentally and theoretically investigated. It is shown that these dyes can form not only ordered J-aggregates but also H-aggregates (differing by the packing angle of dye molecules in an aggregate and having other spectral characteristics) in the outer shell of the hybrid nanostructure. Absorption spectra of synthesised three-layer nanorods are recorded, and their sizes are determined. The optical properties of the composite nanostructures under study are found to differ significantly, depending on the type of the molecular aggregate formed in the outer shell. The experimental data are quantitatively explained based on computer simulation using the finite-difference time-domain (FDTD) method, and characteristic features of the plasmon–exciton interaction in the systems under study are revealed.