Rod-shaped Au@PtCu nanostructures with enhanced peroxidase-like activity and their ELISA application

Pt and its based alloy nanoparticles (NPs) have been reported to demonstrate novel enzyme-like activities. Varying composition is very important to realize the optimization of their functions through the tuning of electronic structure. In this paper, our effort is focused in this direction by tailoring the electronic structure of Pt NPs via alloying with copper. Using gold nanorod (Au NR) as core, a simple method to prepare PtCu alloy shell is developed (termed as Au@PtCu NR). The introduction of copper could result in endcap-preferred growth mode owing to the lattice mismatch between alloy shell and the Au core. The variation in the electronic structure changes the substrate affinity, and enhanced affinity was found for H2O2. Besides, the designed Au@PtCu nanostructures have realized spatial separation of catalytic and recognition sites. Binding of recognition antibodies had negligible effect on their catalytic activity. Based on their peroxidase-like activity, a highly sensitive detection of human immunoglobulin G (IgG) was demonstrated in a direct enzyme-linked immunosorbent assay (ELISA) mode. The detection limit can be as low as 90 pg/mL.