Amplified electrochemiluminescence signals promoted by the AIE-active moiety of D–A type polymer dots for biosensing†
Three-component conjugated polymers of a strong donor–acceptor (D–A) type could be synthesized by Pd-catalyzed Suzuki coupling polymerization reaction of 1,2-bis(4-bromophenyl)-1,2-diphenylethene (M-1) with 9-octyl-3,6-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole (M-2) and 4,6-bis((E)-4-bromostyryl)-2,2-difluoro-5-phenyl-2H-1l3,3,2l4-dioxaborinine (M-3). Among them, P-1 and P-2 with high TPE ratios at 0.95 and 0.9 showed obvious aggregation-induced emission (AIE) behavior; in contrast P-3 with a low TPE ratio at 0.8 showed an aggregation-caused quenching (ACQ) phenomenon. In particular, the three resulting polymer dots (P-1 to P-3 Pdots) exhibited a 200 mV lower electrochemiluminescence (ECL) potential due to their strong D–A electronic structure. Most importantly, the ECL signals of Pdots could be enhanced as high as 3 times by increasing their AIE-active TPE moiety ratios from 0.8 (P-3) to 0.95 (P-1) via the band gap emission process. Herein, P-1 Pdots with the strongest ECL signal were successfully used as ECL biosensors for the detection of catechol, epinephrine and dopamine with detection limits of 1, 7 and 3 nM, respectively. This work provides a new strategy for developing highly sensitive ECL biosensors by the smart structure design of the AIE-active Pdots.