A highly selective and sensitive oligomers-based fluorescent sensor for Cu2+detection in aqueous solution incorporating pillar[5]arene and imidazo [4,5-f][1,10]phenanthroline moieties

A conjugated oligomers (Co-P[5]ImPhen) containing pillar[5]arene (P[5]) unit as fluorophore and 1H imidazo [4,5-f][1,10]phenanthroline (ImPhen) unit as recognition group was designed and synthesized by Suzuki coupling. The Co-P[5]ImPhen has good fluorescent performance in DMSO aqueous solutions. The Co-P[5] ImPhen has an excellent selectivity and sensitivity for Cu2+ detection in DMSO/H2O (1:3, v:v) solution while showing fluorescence quenching response to Cu2+ (1 - I/I0= 94.2%) and excellent anti-interference ability against paraquat analogs and metal ions. Additionally, the Stern-Volmer quenching constant (Ksv) was calculated to be 2.544 x 106 M-1 by fluorescence titration, indicating that the oligomer has strong binding capacity to Cu2+. The detection limit for Cu2+ was remarkably low (1.17 x 10-10 M). The binding mechanism of Co-P[5]ImPhen with Cu2+ was verified utilizing 1H NMR spectra and quantum chemical calculations. The study indicated that the Co-P[5]ImPhen interacts with Cu2+ primarily through two nitrogen atoms on phenanthroline. Furthermore, the oligomers Co-P[5]ImPhen showed potential application in the detection of Cu2+ in practical samples.