One-Pot Synthesis of Hat-like PdAu Alloy Open Nanostructures with Improved Oxidase-like Activities

Controlled assembly of two-dimensional (2D) noble metal nanocrystals into three-dimensional (3D) open architecture with reasonable interparticle distance is of great value to solve the re-stacking issue for practical application, which yet achieves limited progress for bimetallic nanocrystals. Herein, we report the synthesis of hat-like palladium-gold (PdAu) alloy nanocrystals with the building block of nanosheet and explored their catalytic properties when serving as oxidase-like nanoenzyme. The success of current synthesis lies on the co-reduction of Au and Pd precursors under kinetics-controlled condition, together with the use of glutathione molecules as the shape-directing agent. The use of OTAC as capping agent is crucial for the unique morphology, where wire-like and quasi-spherical products are obtained, respectively, when the capping agent is replaced by CTAB and CTAC, respectively. Systematic investigations reveal that the oxidase-like activities of these PdAu nanocrystals are highly morphology-dependent. In particular, the PdAu alloy nanohats displayed the highest oxidase-like activity, as well as a wide linear range (100-5000 mu M) and low detection limit (25 mu M). The present study drives the development of synthetic strategies that allows the construction of 2D bimetallic nanocrystals with a 3D open structure, and validates their improved performance as nanoenzyme towards practical sensing applications, which may find important use in the rational design of biocatalysis, bioassays, and nano-biomedicine.