Fluorescence quenching amplification in silica nanosensors for metal ions

Abstract

We report here the synthesis, photophysical characterization and ion binding ability of new silica nanoparticles bearing covalently linked luminescent chemosensors. These moieties possess a dansyl unit as a fluorophore and a polyamine chain as a receptor. Interestingly, the addition of copper, cobalt and nickel ions induces a strong quenching of the fluorescence intensity even at nanomolar concentrations. The results obtained suggest that each ion can quench up to 13 dansyl units, leading to strong signal amplification. This is possible because the nanoparticle structure, in which a high density of chemosensor units is present, allows the occurrence of multicomponent cooperative photophysical processes. In our opinion, the versatility of this approach opens up new perspectives for the design of a new class of photonic devices at the nanometric level.