Nanoparticle-Induced Enhancement and Suppression of Photocurrent in a Silicon Photodiode

Nanoparticles are capable of both enhancing and suppressing the photocurrent in a silicon diode when deposited on the active face of the device. Photocurrent imaging of the individual nanoparticles and nanoparticle aggregates responsible for this effect reveals that Au nanospheres, nanoshells, and nanoshell dimers each exhibit unique wavelength-dependent suppression-enhancement characteristics. In contrast, silica nanospheres provide a sizable and relatively uniform photocurrent enhancement across the same spectral range (532−980 nm). Unusual light-harvesting behavior observed correlates with a highly complex energy flow (optical “vortexing”) for the forward scattered light of plasmon resonant nanoparticles into the device

Au Nanorice Assemble Electrolytically into Mesostars

Star-shaped mesotructures are formed when an aqueous suspension of Au nanorice particles, which consist of prolate hematite cores and a thin Au shell, is subjected to an electric current. The nanorice particles assemble to form hyperbranched micrometer-scale mesostars. To our knowledge, this is the first reported observation of nanoparticle assembly into larger ordered structures under the influence of an electrochemical process (H2O electrolysis). The assembly is accompanied by significant modifications in the morphology, dimensions, chemical composition, crystallographic structure, and optical properties of the constituent nanoparticles

Au Nanorice Assemble Electrolytically into Mesostars

Star-shaped mesotructures are formed when an aqueous suspension of Au nanorice particles, which consist of prolate hematite cores and a thin Au shell, is subjected to an electric current. The nanorice particles assemble to form hyperbranched micrometer-scale mesostars. To our knowledge, this is the first reported observation of nanoparticle assembly into larger ordered structures under the influence of an electrochemical process (H2O electrolysis). The assembly is accompanied by significant modifications in the morphology, dimensions, chemical composition, crystallographic structure, and optical properties of the constituent nanoparticles

Nanoshells Made Easy: Improving Au Layer Growth on Nanoparticle Surfaces

The growth of a continuous, uniform Au layer on a dielectric nanoparticle is the critical step in the synthesis of nanoparticles such as nanoshells or nanorice, giving rise to their unique geometry-dependent plasmon resonant properties. Here, we report a novel, streamlined method for Au layer metallization on prepared nanoparticle surfaces using carbon monoxide as the reducing agent. This approach consistently yields plasmonic nanoparticles with highly regular shell layers and is immune to variations in precursor or reagent preparation. Single particle spectroscopy combined with scanning electron microscopy reveal that thinner, more uniform shell layers with correspondingly red-shifted optical resonances are achievable with this approach