Optical properties and photoinduced aggregation of cyanine dyes on silver island films

The optical properties and photoinduced modification of hybrid nanostructures, which are silver island films coated with a layer of cyanine dye, were studied. Experiments were conducted on three dye homologs and films differing in the equivalent thickness of the deposited silver. It was shown that the absorption of a hybrid film is not the sum of the absorption of the molecular layer and the plasmon absorption of the silver. The near fields of nanoparticles (NPs) that form island films increase the absorption of organic molecules, with the greatest increase observed in the band of J-aggregates. The influence of the near fields can be reduced by distancing the molecules from the NPs using an insulating polymer layer. In the presence of silver NPs, the photoinduced modification of the component composition of the layers of the dyes occurs at far lower energy densities. Resonant nanosecond laser pulses lead to the aggregation of molecules in hybrid films.