Metal oxide semiconductor nanocrystals (NCs), which emerged as a novel class of electrochemiluminescence (ECL) emitters with low cost and good biocompatibility, have attracted particular research interests in ECL biosensors. However, their analytical applications still remained a substantial challenge of relatively low ECL intensity. Herein, the novel self-accelerated ECL emitters of silver nanoparticles functionalized SnO2 nanoflowers (Ag@SnO2 NFs) were first prepared by in situ generating silver nanoparticles on the surface of SnO2 nanoflowers via silver mirror reaction, which exhibited high-intensity ECL emission with the maximum emission peak at 542 nm in the case of S2O82- as a co-reactant. It was worthy to note that compared with traditional ECL emitters of SnO2 NCs with diameters below 10 nm, the obtained Ag@SnO2 NFs with diameters about 1-2 mu M showed a stronger ECL emission. The ECL enhancement was supposed to derive from 1) the strong size effect of flower-like nanostructure aggregating by ultrathin SnO2 nanosheets, which would offer large amount of tin interstitials or oxygen vacancies; 2) the in situ generated silver nanoparticles (Ag NPs) as co-reaction accelerator, which would generate more oxidizing intermediate (SO4 center dot-) to significantly self-promote the ECL emission of Ag@SnO2 NFs. Given these attributes, we developed a sensitive ECL immunosensor for the detection of cardiac troponin T (cTnT) utilizing Ag@SnO2 NFs as efficient signal probes, which showed outstanding sensitivity with a favorable linear range from 1 fg/mL to 100 pg/mL and relatively low detection limit of 0.11 fg/mL. This work efficiently offered insights into the promising applications of Ag@SnO2 NFs as a low toxicity and superior ECL emitter in ECL bioanalysis. (C) 2018 Elsevier Ltd. All rights reserved.