Thioflavin-T-Enhanced Fluorescence in Cerium Adenosine Triphosphate Coordination Polymer Nanoparticles for Selective and Sensitive Copper(II) Detection in E-Waste and Biological Samples

Coordination polymer nanoparticles (CPNs) are a unique class of nanoparticles designed via the self-aggregation of a metal ion and a polydentate ligand. Among them, lanthanide-based CPNs are considered to be the most promising due to their intrinsic luminescent properties, stability in different oxidation states, and high coordination flexibility. In the present study, cerium-based coordination polymer nanoparticles (Ce-CPNs) have been synthesized using adenosine triphosphate (ATP) as a cross-linking ligand. A weakly emissive molecular-rotor-type dye, Thioflavin-T (ThT), was incorporated into the porous polymeric network of CPNs, which led to a drastic enhancement in the emission intensity of ThT. The emission intensity of ThT-Ce(III)-ATP-Tris CPNs is severely quenched in the presence of Cu(II) ions, which has been utilized for the detection of Cu(II). The sensing mechanism was established by using photophysical techniques such as absorbance, emission, excited-state lifetime, and particle size measurements. The selectivity of this methodology for Cu(II) ions was checked by studying the interference of several metal ions, anions and biomolecules. The limit of detection (LOD) obtained for Cu(II) in the present methodology was about 660 nM (42 ppb), which is far below the U.S. EPA prescribed limit (20 μM) in water. The present methodology was successfully demonstrated to determine the Cu(II) concentration in e-waste leachate and also in spiked human serum samples. The LOD of Cu(II) in diluted e-waste leachate was found to be marginally higher (730 nM) compared to that in the case of water, whereas the LOD in 10% (v/v) serum was to be 5 μM (320 ppb).