A highly selective and sensitive probe based on benzo[1,2-b:4,5-b′]dithiophene: synthesis, detection for Cu(II) and self-assembly

A novel turn-off probe for copper(II) containing benzo[1,2-b:4,5-b′]dithiophene (BDT) and two picolinamide units was synthesized. In this probe, two picolinamide units complex with one Cu2+ ion and two nitrogen atoms in each picolinamide unit coordinate with Cu2+, which is verified by DFT calculation. Its fluorescence quantum yield is 0.43 and the detection limit is as low as 2.4×10−8 mol/L. The results show that the probe displays good selectivity for Cu2+ over other ions (Mn2+, Pb2+, Cr3+, Zn2+, Ni2+, K+, Ca2+, Ag+, Mg2+, Fe3+, Fe2+, Hg2+, Al3+, Cd2+, Pd2+, Co2+). Furthermore, the probe induced by Cu2+ and the π–π interaction of the aromatic unit can also form rod structure assembly, which can be observed by scanning electron microscopy (SEM).