Kinetical Evolution from Icosahedrons to Triangular Nanotripods: Factors Affecting Symmetry Breaking in Au–Cu Multiply Twinned Nanoparticles, Ligand Exchange, and Repercussion in the Catalytic Activity

Anisotropic bimetallic multiply twinned nanoparticles possess unique properties that depend not only on the shape but also on the crystal and defect structures. Hence, control over the synthesis parameters is paramount to control the reaction kinetics, obtaining symmetric or anisotropic nanoparticles with a tunable crystal and defect structure. Herein, we report the kinetic control for the growth of Au–Cu anisotropic nanoparticles synthesized through a seed-mediated approach, enabling the evolution from Au icosahedral seeds to symmetrical Au–Cu nanoparticles or multiply twinned Au–Cu triangular nanotripods. The anisotropic growth was induced by maneuvering the metal-to-seed ratio and temperature. The effects of the metal-to-seed ratio, temperature, and Cu/Au ratio were determined, providing information on the role of these parameters in the reaction. The presence of Cu in this oleylamine (OLA)-based synthesis is decisive for the anisotropic growth, enhancing particle growth and homogeneity. Evolution experiments showed a cyclic-type growth pathway of the nanotripods. The enhanced catalytic properties of the produced Au–Cu multiply twinned nanotripods were tested in the reduction of 4-nitrophenol, for which a ligand exchange was carried out replacing oleylamine capping for poly(diallyldimethylammonium) chloride. The Au–Cu nanotripods showed high activity with a low metal loading.