A “Talking” between Gold Nanoparticle and a Luminescent Iridium(III) Complex: A Study of the Effect Due to the Interaction between Plasmon Resonance and a Fluorophore

This paper explores a novel synthesis and characterization of silica-coated gold nanorods (AuNRs) embedding a highly emissive cyclometalated iridium(III) complex, denoted as Ir1. We investigate the optical properties and the interplay between the metal compound and gold plasmon, observing how the emission of Ir1 incorporated into the nanoparticles shows two emission bands, one in the blue and the other in the green-orange range of the visible spectrum. To obtain a clearer picture of what we were observing, we synthesized analogous nanosystems, from which it was possible to highlight the effect of different features. Based on what we observed, we proposed that the fraction of the iridium(III) complex in direct contact with the surface of the gold nanoparticle undergoes a “demixing” of the excited state, which, for cyclometalated iridium complexes, is generally considered a mixed LC+MLCT state. This preliminary study sheds light on the complexity of the “talking” between a fluorophore and a plasmonic system, highlighting the importance of considering the emitter typology when modeling such systems.