Dual-emission fluorescent probe templated by spherical polyelectrolyte brush for ratiometric detection of copper ions

A novel ratiometric fluorescent probe for Cu²⁺ was fabricated in spherical polyelectrolyte brush (SPB) where the red-emission europium complex Eu(TTA)₃Phen was embedded in the polystyrene (PS) core to generate the reference signal and the green-emission glutathione-capped CdTe quantum dot was immobilized onto the poly(styrene sulfonate) brush shell to provide the sensing signal.Results indicate that this probe has high sensitivity and selectivity for Cu²⁺ over other metal ions. The addition of Cu²⁺ could greatly quench the probe’s fluorescence at 550 nm, while the fluorescence signal at 614 nm kept unchanged. Under the optimized conditions, the intensity ratio of the two fluorescence emissions showed a linear response range from 0 to 1000 nM with a limit of detection of 1.45 nM for Cu²⁺. The probe is very suitable for the detection of copper contamination with quick response, low cost and great stability. SPB was proved to be an excellent “carrier” for building high-quality ratiometric probes due to its special core–shell structure and outstanding ability to enrich counterions. This work provides a versatile method for the development of high-quality ratiometric fluorescent probes, which can be extended to potential applications in various fields, such as environmental monitoring, biological imaging, pathological analysis and cancer diagnosis.