Investigation of Photophysical and Electrofluorochromic Properties of Gold Nanoparticles Functionalized by a Luminescent Electroactive Complex

Gold nanoparticles (6 nm diameter) functionalized by a luminescent electroactive iridium complex have been synthesized, leading to stable colloidal suspensions in o-dichlorobenzene, a high boiling point solvent. The photophysical properties of these functionalized nanoparticles have been investigated showing a partial quenching of iridium emission by the gold core. Fluorescence correlation spectroscopy has been used to demonstrate that all the iridium complex is actually located on the nanoparticle surface, allowing the investigation of the electrofluorochromic behavior to be investigated for the first time in colloidal plasmonic systems. Compared with the free complex in solution, which shows a well-defined reversible electrochemically monitored luminescence (electrofluorochromism), the iridium-functionalized nanoparticles display a much less pronounced and less potential-dependent electrofluorochomic behavior, unless the potential is pushed toward values where gold stripping occurs.