A Strategy for the Formation of Gold-Palladium Supra-Nanoparticles from Gold Nanoparticles of Various Shapes and Their Application to High-Performance H2O2 Sensing

We present a new approach for the synthesis of gold (Au)-palladium (Pd) bimetallic supra-nanoparticles in which densely packed anisotropic Pd nanostructures surround a central Au nanoparticle (rod, sphere, cubic shape). They were obtained by means of Pd crystal growth on Au nanoparticle surfaces which are modified with a mixture of cetyltrimethylammonium bromide (CTAB) and 5-bromosalicylic acid (5-BrSA). From a comparative study with a Au nanorod (NR) as a seed, the use of the CTAB/5-BrSA mixture plays a pivotal role in obtaining such unique supra-structures; the Au NR capped with only CTAB resulted in Au corecontinuous Pd shell nanoparticles instead. The AuPd supra-nanoparticles provide active surface area for electrocatalytic activities higher than that of the Au@Pd continuous shell nanoparticles, displaying outstanding performance for mediator-free electrochemical detection of H2O2