Formation of diverse supercrystals from self-assembly of a variety of polyhedral gold nanocrystals.

Cubic, rhombic dodecahedral, octahedral, and corner-truncated octahedral gold nanocrystals with sizes of tens of nanometers have been used as building blocks to form micrometer-sized supercrystals by slowly evaporating a water droplet on a substrate placed in a moist environment. Drying the droplet at 90 °C was found to yield the best supercrystals. Supercrystals were evenly distributed throughout the entire substrate surface originally covered by the droplet.

Fast synthesis of PbS nanocrystals in aqueous solution with shape evolution from cubic to octahedral structures and their assembled structures.

In this study, we have developed for the first time a fast and energy-efficient method for the synthesis of PbS nanocrystals with systematic shape evolution from cubic to truncated cubic, cuboctahedral, truncated octahedral, and octahedral structures. The method involves the addition of a small volume of preheated lead acetate and thioacetamide (TAA) mixture to an aqueous growth solution of lead acetate, thioacetamide, cetyltrimethylammonium bromide, and nitric acid. By varying the amount of thioacetamide added to the growth solution, PbS nanocrystals with different morphologies were generated in 2 h at 90 °C.

Fabrication of Au-Pd core-shell heterostructures with systematic shape evolution using octahedral nanocrystal cores and their catalytic activity.

By using octahedral gold nanocrystals with sizes of approximately 50 nm as the structure-directing cores for the overgrowth of Pd shells, Au-Pd core-shell heterostructures with systematic shape evolution can be directly synthesized. Core-shell octahedra, truncated octahedra, cuboctahedra, truncated cubes, and concave cubes were produced by progressively decreasing the amount of the gold nanocrystal solution introduced into the reaction mixture containing cetyltrimethylammonium bromide (CTAB), H(2)PdCl(4), and ascorbic acid. The core-shell structure and composition of these nanocrystals has been confirmed.

A comparative study of gold nanocubes, octahedra, and rhombic dodecahedra as highly sensitive SERS substrates.

Gold nanocubes, octahedra, and rhombic dodecahedra with roughly two sets of particle sizes have been successfully synthesized via a seed-mediated growth approach. All six samples were analyzed for comparative surface-enhanced Raman scattering (SERS) activity. All of these Au nanostructures were found to yield strong enhancement at a thiophenol concentration of 10(-7) M and are excellent SERS substrates.