Mutual influence of gold and silver nanoparticles on Tris-(2,2′bipyridine)-Ru(II) core complexes: Post-functionalization processes, optical and electrochemical investigations

The synthesis, reactivity and properties of a series of four polypyridyl ruthenium complexes have been studied. These complexes were used to post-functionalize preformed 3 nm silver and gold nanoparticles (NPs) in water and in dichloromethane (DCM). We studied the influence of the grafted complexes on the formation process and stability of the colloidal solutions and we investigated the optical and electrochemical properties of the final nanocomposites. Among the series of four ruthenium complexes, three novel heteroleptic complexes (1–3) bearing one pyridine, one amine or two carboxydithioic acid pendant groups were synthesized and reacted with preformed Au-NPs and Ag-NPs. Results were compared to those obtained with the model [Ru(bpy)₃]²⁺ complex (4). The strength of the interaction between the anchoring group and the surface of NPs influenced the size, shape and stability of the final nanocomposites. Polar solvent such as water induced aggregation and lead to unstable nanocomposites. Stationary and time resolved luminescence of grafted nanocomposites (1–3) showed that the luminescence of complexes were completely quenched (lifetime and emission quantum yield) in water by electron transfer processes, moreover electrical measurements rationalize that Ag nanocomposites exhibit the stronger quenching due to a lower oxidation potential. It also showed a current enhancement associated with double layer charging of the metal nanoparticle cores.