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.