Asymmetric Deposition of Platinum Atoms on Gold Nanorods Reduced the Plasmon Field Distortion Induced by the Substrate

New anisotropic bimetallic nanoparticles are prepared on the surface of a substrate with different structures. Unlike the homogenous deposition of Pt on the surface of colloidal gold nanorods (AuNRs), Pt atoms deposit on the surface of AuNRs organized into 2-D arrays binding to a substrate inhomogeneously. Pt ions are chemically reduced and deposit on the surface of AuNR 2-D arrays. Pt atoms deposit initially at the tips of the AuNRs and the magnitude increases over time. After a complete coverage of the tips, the deposition proceeds on the side of the AuNR 2-D arrays. The mechanism of breaking the symmetry of the deposition of Pt on AuNRs is discussed. Individual AuNRs displayed different optical responses depending on the location of the deposited Pt. The experimental optical results are validated theoretically and correlated to the configuration of the Pt layer, imaged by high-resolution electron microscopic imaging. Plasmonic nanoparticles exhibit field distortions when placed on a substrate, which leads to an increased field intensity on the nanoparticle close to the substrate increased at the expense of the intensity of the field intensity on top of the nanoparticles. Interestingly, the plasmon field distortion by the substrate is lowered upon Pt deposition. The prepared nanoparticle 2-D arrays are useful in photocatalysis and optically enhanced catalysis as they compromise an exciting plasmonic metal and a catalytically efficient metal.