Design, preparation, and optical characterization of plexcitonic nanohybrids based on gold nanorods and J-aggregates of organic dyes

The light-matter coupling has long been investigated due to its potential disruptive applications. In fact, hybrid light-matter systems promise to unlock an unprecedented capability of directing the migration of excitation energy at the nanoscale, offering exciting prospects in the field of quantum technologies, light-harvesting, and all those photonic applications that require strict control over the flow of energy in time and space. Plexcitonic nanohybrids, a class of light-matter strongly coupled systems, are nanomaterials characterized by plasmon-exciton couplings. In this Thesis, we synthesized nanohybrids systems based on gold nanorods and J-aggregates of two different cyanine molecules. These nanomaterials have been characterized by UV-Vis absorption, circular dichroism, and pump-probe spectroscopy. We found that it is possible to tune the final optical and dynamical properties by using a mixture of the two different dyes. Furthermore, we observed dynamics that are compatible with the presence of ‘one-particle’ and ‘two-particle’ states that, together with dark states, seem to be involved in a complex process of energy redistribution in the picoseconds timescale. Although further work is necessary to confirm these conclusions, the data in this Thesis provide important information for better comprehension and exploitation of plexcitonic nanohybrids.