Description:

No, they are not eggs of nano-chickens!  This image shows an aggregate of half-shells of palladium deposited onto a silicon wafer and observed by scanning electron microscopy. The half-shells have a diameter of 300 nm and a shell thickness of 8 nm. The half-shells were false-colored (yellow) to distinguish them from the underlying silicon substrate.

The deposition of a thin, metal film onto an array of spherical silica nanoparticles, followed by dissolving the silica particle template, produces metallic half-shells with nanometer-scale dimensions. Half-shells of gold, platinum, and palladium were fabricated, with diameters of the particles ranging from 100 to 500 nm, and shell thicknesses of 8-15 nm. The half-shells have three useful properties because of their geometries: (i) a high ratio of surface area to volume, (ii) a large length of edge relative to size, and (iii) an entropic resistance to assembling into close-packed structures. The surface properties of these half-shells can be modified with self-assembled monolayers (SAMs) , formed by adsorption of alkanethiols (a sulfur terminated organic molecule).

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