3D hierarchical ZnNiO2 nanoflowers as a novel co-reaction accelerator to fabricate stable and highly sensitive biosensor for the methotrexate assay

Herein, polyaniline (PANI) and reduced graphene oxide (rGO) as nanoprobes couple with graphitic carbon nitride to form rGO@g-C 3 N 4 -PANI nanocomposite, which exhibits good synergetic enhancement impact on the ECL signal of g-C 3 N 4 . Moreover, ZnNiO 2 nanoflowers (ZnNiO 2 NFs) are firstly used as co-reaction accelerators to remarkably enhance the ECL emission of rGO@g-C3N4-PANI in this work. In the presence of ZnNiO2 NFs, a significant ECL signal enhancement of 15780 a.u. is observed, which is 4 times stronger than that of the rGO@g-C3N4-PANI. Owing to the excellent electronic conductivity and the ability to avoid the deposition of positively charged reduction products, the ZnNiO2 NFs can effectively prevent electrode passivation , thus the rGO@g-C3N4-PANI/ZnNiO2 system emits stable and strong ECL signal. A sensitive ECL sensor has been constructed for the quantitative detection of methotrexate (MTX) of the real blood sample by quenching the ECL signal. Under the optimal conditions, the sensor exhibits a superior linear range from 1 pM to 10 μM and a low detection limit of 0.24 pM (S/N = 3). The proposed ECL signal amplification strategy can be an effective analytical tool for trace detection of targets in biological systems.