Fig shows the negative ECL emission curve

The schematic diagram of fabrication of the sandwich-type ECL immunosensor was shown in Fig. 1. Firstly, SM-164 GCE was polished with 0.05 μm alumina slurry until a mirror shiny surface appeared, and then cleaned thoroughly before using. The electrodeposited of GNPs on the electrode surface was carried out by constant potential electrolysis at -0.2 V for 300 s in 0.5 M H2SO4 solution containing 5 mM HAuCl4. After washing, Ab1 (10 μL, 30 μg/mL) was dropped onto the electrode surface and incubated at 4 °C over night. Following that, the electrode was washed and blocked with 10 μL of 1 wt% BSA solution for 1 h. Afterwards, the electrode was washed and incubated with a varying concentration of MCLR for 30 min at room temperature, and then diencephalon was washed to remove unbounded MCLR molecules. Finally, the electrode was immersed in the as-prepared QDs-Ab2 solution for 1 h at room temperature, and the electrode was washed thoroughly for measurement.