▎ 摘　　要

Up to now, tris(2,20-bipyridine)ruthenium(ii) (Ru(bpy)32+) has been widely used in electrochemiluminescence (ECL) detection. However, very positive (>1.0 V vs Ag/AgCl) or negative potential (near -2.0 V vs Ag/AgCl) has to be applied to trigger its ECL. In this work, Ru(bpy)32+ could obtain an intensive and stable cathodic ECL at an excitation voltage of -0.2 V (vs Ag/AgCl) on porous partially reduced graphene oxide (PPRGO), attribut-ing to its excellent electrochemical performance toward oxygen reduction reaction. The mild potential could prevent the electronic damage to the biomolecules. Based on quenching effect of MoS2 nanoflowers, the catho-dic ECL was used to construct a sandwich "signal-off" ECL immunosensor, which achieved a sensitive detection of carcinoembryonic antigen (CEA) under optimized conditions. A linear calibration curve from 10 fg mL-1 to 10 ng mL-1 was obtained with the low detection limit of 2.6 fg mL-1 (S/N = 3). In addition, the sensor demonstrated good specificity, stability and reproducibility, and the detection of actual samples obtained sat-isfactory results. The proposed strategy has a potential application prospect in clinical detection.