▎ 摘　　要

An electrochemiluminescent immunosensor is constructed for the detection of diethylstilbestro (DES) on the basis of amplified quenching of electrochemiluminescence (ECL) from CdTe nanocrystal (NC)/reduced graphene oxide (rGO) composite films by antibody (Ab) against DES-modified SiO2 nanoparticles (Ab@SiO2). In this immunosensing system, CdTe NC/ rGO composite films act as solid supporters for both DES and ECL emitters, which generate a 100-fold stronger ECL emission than CdTe NC films because the presence of rGO can lower the potential barrier, facilitate charge transfer, suppress nonradiative Auger recombination, and make the electron trap states fill more efficiently. On the composite films, the immobilized ovalbumin-modified DES (OVA-DES) competes with free target DES to bind Ab@SiO2 As a result, the number of formed OVA-DES-Ab@SiO2 immunocomplexes is inversely related to that of target DES. Using an ECL quenching maximum at blank as a calculation benchmark, the ECL intensity increment of the immunosensor and the concentration of target DES show a linear range of 0.002-2 ng/mL (R-2 = 0.996) with a detection limit of 0.001 ng/mL (signal/noise = 3). This immunosensor, of good selectivity and stability, was used to detect beef samples, with recoveries at a scope of 93.2%-105.0%.