Enhanced ECL Emission in Coreactant-Free Aqueous Environments Using Ru(bpy)32+/amine-Doped Silica Nanoparticles

Innovative ECL systems based on dye-doped silica nanoparticles (NPs) were developed to overcome the limitations of traditional coreactant-based ECL systems, in particular those related to coreactant toxicity and coreactant diffusion dynamics. The synthesis of these colloidal systems was carried out through a reverse microemulsion method, focusing on identifying the most effective strategy for producing functionalized and stable NPs. The developed systems consisted of two kinds of Ru(II) polypyridine complexes as the photoactive species and tertiary aminosilanes covalently bound to the silica structure, acting as coreactant moieties. The synthetic approach was designed to produce a precise core-shell NP structure, ensuring both the stability of the colloids and their high photoluminescence emission efficiency. Three aminosilanes at different concentrations were introduced in different sets of NPs doped with the complex Ru(bpy)32+ (tris(2,2′-bipyridine) Ruthenium(II)) or with a Ru(II) poly-bipyridine complex derivatized with a triethoxysilane group for covalent anchoring to the silica matrix. These NPs were characterized from the morphological and photophysical perspective, and their ECL emission properties were then investigated. The results obtained with these dye-doped silica NPs are very promising for the future development of ECL labels and for ECL imaging applications in relevant biological media such as cellular environments.