Electrochemiluminescence behaviour of silver/ZnIn2S4/reduced graphene oxide composites quenched by Au@SiO2 nanoparticles for ultrasensitive insulin detection

Herein, an effective electrochemiluminescence resonance energy transfer (ECL-RET) immunosensing strategy was proposed using silver/ZnIn2S4/reduced graphene oxide composites (Ag/ZnIn2S4/RGO) as the ECL donor and gold decorated silicon dioxide nanoparticles (Au@SiO2 NPs) as the ECL acceptor. ZnIn2S4 nanosheets (NSs), which exhibited strong ECL emission in the presence of potassium persulfate (K2S2O8) with ECL spectral band at 370–720 nm, were in situ grew on the RGO surface (ZnIn2S4/RGO) by a facile one-step hydrothermal method. Integrating with the morphological and electrical superiorities of RGO and AgNPs, the ECL emission of ZnIn2S4 at 551 nm was dramatically enhanced. Moreover, Au@SiO2 NPs whose UV–vis absorption spectra at 450–650 nm were firstly fabricated as a matched ECL acceptor for Ag/ZnIn2S4/RGO. Due to the fine spectral overlap between the ECL emission spectra of ZnIn2S4 NSs and the absorption spectra of Au@SiO2 NPs, efficient ECL quenching was induced for the sensitive responses and accurate quantification of insulin in real samples. Given the excellent linearity performed in 0.1 pg/mL - 80 ng/mL and the low detection limit achieved at 0.034 pg/mL (S/N = 3), the highly-efficient ECL-RET immunosensor holds splendid potential in detecting insulin and other biomarkers in human serum for the early diagnostics of serious diseases. •ZnIn2S4 nanosheets were firstly exploited as luminescent ECL materials and energy donor in ECL-RET system.•Au@SiO2 nanoparticles can quench the ECL emission of ZnIn2S4.•ECL emission spectrum of ZnIn2S4 significantly overlapped with UV–vis spectrum of Au@SiO2 nanoparticles.•Sensitive detection of insulin was realized with good selectivity, reproducibility and stability.