Synthesis of silica nanoparticles doped with [Ru(bpy)3]2+ and decorated with silver nanoclusters for the ratiometric photoluminescent determination and intracellular imaging of Cu(II) ions

A sensitive and selective luminescent nanoprobe (referred to as DEPN) is designed for the determination of Cu(II) ions. DEPN shows two emission peaks, one at 602 nm and caused by [Ru(bpy) 3 ] 2+ , the other (peaking at 500 nm) caused by silver nanoclusters (AgNCs). The luminescence of the ruthenium complex is inert and acts as the internal reference signal, while that of the AgNCs is quenched by Cu(II) ions. Under 350 nm photoexcitation, a linear relationship is found between the ratio of emission intensity (I 500 /I 602 ) and the concentration of Cu(II) ions in the 0.1–16 μM range. The detection limit of Cu(II) ions is estimated to be 50 nM. The DEPN was applied to the determination of Cu(II) ions in (spiked) water samples, and to intracellular imaging of Cu(II) in HeLa cells using confocal fluorescence microscopy. Schematic presentation of a dual-emission photoluminescence nanoprobe for selective Cu 2+ sensing. The emission of the Ag nanoclusters (at 500 nm) is quenched by Cu 2+ , while that of the Ru(bpy) 3 2+ -doped silica nanoparticles (at 602 nm) remains unchanged and serves as a reference.