•A novel ternary graphene/SnO2/Au was synthesized.•High sensitive and label-free electrochemical immunosensor for detection of α-fetoprotein was developed.•The proposed electrochemical immunosensor was successfully applied to the determination of AFP in serum samples.A label-free electrochemical immunosensor for sensitive detection of α-fetoprotein (AFP) was developed based on graphene/SnO2/Au nanocomposite. The graphene/SnO2/Au nanocomposite modified glassy carbon electrode was used to immobilize α-fetoprotein antibody (anti-AFP) and to construct the immunosensor. Results demonstrated that the peak currents of [Ru(NH3)6]3+ decreased due to the interaction between antibody and antigen on the modified electrode. Thus, a label-free immunosensor for the detection of AFP was realized by monitoring the peak current change of [Ru(NH3)6]3+. The factors influencing the performance of the immunosensor were investigated in details. Under optimal conditions, the peak currents obtained by DPV decreased linearly with the increasing AFP concentrations in the range from 0.02 to 50 ng mL−1 with a linear coefficient of 0.9959. This electrochemical immunoassay has a low detection limit of 0.01 ng mL−1 (S/N=3) and was successfully applied to the determination of AFP in serum samples.

In this article, a clean method for the synthesis of PtPd/reduced graphene oxide (RGO) catalysts with different Pt/Pd ratios is reported in which no additional components such as external energy (e.g., high temperature or high pressure), surfactants, or stabilizing agents are required. The obtained catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), induced coupled plasma atomic emission spectroscopy (ICP–AES), and electrochemical measurements. The HRTEM measurements showed that all of the metallic nanoparticles (NPs) exhibited well-defined crystalline structures. The composition of these Pt–Pd/RGO catalysts can be easily controlled by adjusting the molar ratio of the Pt and Pd precursors. Both cyclic voltammetry (CV) and chronoamperometry (CA) results demonstrate that bimetallic PtPd catalysts have superior catalytic activity for the ethanol oxidation reaction compared to the monometallic Pt or Pd catalyst, with the best performance found with the PtPd (1:3)/RGO catalyst. The present study may open a new approach for the synthesis of PtPd alloy catalysts, which is expected to have promising applications in fuel cells.Keywords: alkaline; electrocatalytic activity; ethanol oxidation; fuel cell; PtPd nanoparticles; reduced graphene oxide;

A relatively new and efficient method is reported here for the purification and arrangement of high-aspect-ratio gold nanorods (AuNRs) using a multiamine surfactant, bis[[(amidoethyl)carbamoyl]ethyl]octadecylamine (C18N3), which strongly adsorbs to the surface of AuNRs. The adsorbed layers of the multiamine surfactant on AuNRs exhibit the ability to deaggregate gold nanoparticles at low pH in an aqueous medium and to promote their aggregation at high pH. Through regulation of the pH of the dispersion medium, a well-ordered arrangement of 99% monodisperse AuNRs was obtained, having dimensions of approximately 18 nm diameter and 353 nm length and an area of several dozens of square micrometers, which is much larger than what has been reported in the literature. A very strong optical absorption in the near-infrared region of as-prepared AuNRs was shown. This strategy of using pH-responsive multiamine surfactant to mediate both the homogenization in shape and the arrangement of nanoparticles provides a new methodology for the formation of nanoparticle assemblies.Keywords: arrangement; homogenization; multiamine surfactant; nanorod; purifying;