Gold and Silver Nanoparticles Functionalized by Luminescent Iridium Complexes: Synthesis and Photophysical and Electrofluorochromic Properties

Gold and silver nanoparticles in the 5 nm range functionalized by luminescent and electroactive iridium complexes are synthesized and characterized. Cyclometalated iridium complexes with a modified phenanthroline ligand bearing a pyridine end group are able to cap gold nanoparticles without changing their size and shape, while for silver the size slightly increases and aggregation starts to occur but without any flocculation. The luminescence of iridium is partially quenched by gold nano- particles even when interactions with the complex do not involve surface functionalization (simple mixture). This quenching is much weaker in the case of silver, and capped nanoparticles retain the same luminescence as the free complex. Both iridium complexes display electrofluorochromism, that is, a reversible electrochemically driven luminescence switch when changing the redox state of the metal center.