Green Synthesis of Reduced Graphene Oxide Decorated with Few-Layered MoS2-Nanoroses and Au/Pd/Ag Trimetallic Nanoparticles for Ultrasensitive Label-Free Immunosensing Platforms

Abstract

The conventional synthetic methods for graphene oxide are based on the reaction of graphite with mixed strong oxidants, which involves the risk of explosion and toxic gases. Herein, we report a facile, safe, and green method to synthesize green graphene oxide (denoted as gGO) using sodium periodate as an effective oxidizing agent feature with lower Raman intensity (ID/IG = 0.65) and higher C/O atomic ratio ( ∼ 5.15). We also discuss the mechanism underlying the direct growth of MoS2 nanoroses (MoS2-NRs) on the in situ synthesized green reduced graphene oxide (grGO), in which the MoS2-NRs are assembled from few-layered MoS2 nanosheets. Due to the highly exposed active edge sites of MoS2-NRs and good electrical coupling with the underlying grGO, the resulting grGO/MoS2-NRs nanocomposite exhibits excellent electrocatalytic activity. Furthermore, the addition of L-proline assisted Au/Pd/Ag trimetallic nanoparticles to the nanocomposite provide a suitable label-free platform for direct antibody immobilization and increase the effective surface area. The as-prepared grGO/MoS2-NRs/AuPdAg nanocomposite was employed as a label-free immunosensing platform for the ultrasensitive detection of ochratoxin A, a food mycotoxin. The proposed immunosensor exhibits an excellent high detection range from 10 fg mL−1 to 150 ng mL−1 and limit of detection (LOD) of 5 fg mL−1 (S/N = 3).