Copper(I) photosensitiser-silica nanoparticle assembly towards enhanced aqueous photoluminescence

Harnessing the luminescence potential of Cu(I) complexes in aqueous media is typically hindered by their poor photostability and altered properties. Here, we report the synthesis, engineering and morphological characterization of a hydrophobic homoleptic copper(I) complex entrapped into silica nanoparticles, Cu-I@SiO2 (where “Cu-I” designates [Cu(2,9-diiodo-1,10-phenanthroline)2]+), as a promising stabilisation strategy towards water-compatible, Cu(I) complex-based luminescence. The polyether chain-decorated nano-objects are spherical with an average diameter of ca. 10.8 ± 1.9 nm. Upon dispersion in water, clear solution-like suspensions were obtained. Significantly, the aqueous suspensions photo-luminesce (Φem = 5.10-4) upon excitation through the Metal-to-Ligand Charge-Transfer transition (MLCT) of the embedded copper(I) complexes. In contrast, the corresponding silica-free molecular complex dissolved in an aqueous environment revealed fully quenched emission. Finally, the use of Cu-I@SiO2 suspensions as luminescent probes is reported, first by assessing their potential use as electrochemiluminescent probes, and second by monitoring the photoluminescence from Cu-I@SiO2 in the presence of whole blood.