Metal plasmon-enhanced lanthanide fluorescent nanoparticles for monitoring aqueous copper ions

Lanthanide-doped nanomaterials displaying intense, explicit, and long-lasting photoluminescence (PL) have gained much attention in sensing and imaging applications. In this work, europium complex Eu(dibenzoylmethane)3(1,10-phenanthroline) was integrated into core-shell magnetoplasmonic nanoparticles (Ag@Fe3O4 MagPlas NPs), forming a photoluminescent MagPlas nanostructure with uniform morphology, sharp PL emission profile, and distinct magnetic response. The Eu-doped MagPlas NPs (Eu-MagPs) with Ag-core exhibited an enhancement of PL intensity and lifetime compared to the non-plasmonic counterpart, owing to the metal plasmon-induced fluorescence enhancement. Moreover, the quenching phenomenon of the Eu-MagP probe was utilized as a platform for active quantification of metal ion concentration, exclusively Cu2+, in aqueous samples. The luminescence intensity from the Eu-doped MagPlas NP was proportionally quenched by Cu2+ in the working range of 0–2 ppm with negligible influences of other common cations and anions. Static quenching was investigated as the main mechanism for selective detection, in which the presence of quenchers did not affect the luminescent lifetime of the hybrid nanostructure. Moreover, Eu-MagPs were integrated into polyacrylamide hydrogels with enhanced customizability toward the varied amounts of Cu2+. This fluorescent MagPlas structure, therefore, can be utilized as versatile, waste-free, fully recoverable testing assays or chemical sensors for on-site environmental analysis, and water quality control.