Synthesis and Structural Characterization of Branched Bimetallic AuPd Nanoparticles with a Highly Tunable Optical Response

Bimetallic nanostructures composed of gold (Au) and palladium(Pd)have garnered increased interest for their applications in heterogeneouscatalysis. This study reports a simple strategy for manufacturingAu@Pd bimetallic branched nanoparticles (NPs), which offer a tunableoptical response, using polyallylamine-stabilized branched AuNPs astemplate cores for Pd overgrowth. The palladium content can be alteredby manipulating the concentration of PdCl4 (2-) and ascorbic acid (AA) that are injected, which permit an overgrowthof the Pd shell up to ca. 2 nm thick. The homogeneous distributionof Pd at the surfaces of Au NPs can be carried out regardless of theirsize or branching degree, which allows for an adjustment of the plasmonresponse in the near-infrared (NIR) spectral range. As a proof ofconcept, the nanoenzymatic activity of pure gold and gold-palladiumNPs was compared, exploring their peroxidase-like activity in theoxidation of 3,3 & PRIME;,5,5 & PRIME;-tetramethylbenzidine (TMB). Thebimetallic AuPd NPs demonstrate an increase in the catalytic propertiesattributed to the presence of palladium at the surface of gold.