Silver Nanocrystals: Self-Organization and Collective Properties

In this paper, the main parameters, which dictate the supracrystalline Structure of silver nanocrystals self-assembled at the micrometer scale, are evidenced. They are the alkyl-chain length, the deposition temperature. the concentration of (lie colloidal solution and the nature of the Substrate. By varying the deposition temperature (from 15 degrees to 50 degrees C), from the same batch of nanocrystals (same size, same coating agent), dense (fcc and hcp) and loose (bee) supracrystals or disordered arrangements (rcp) are produced. By tuning the nature of the Substrate (HOPG or amorphous carbon) and its temperature, the final Size Of the supracrystals is controlled. Collective properties due to either nanocrystals ordering in 2D superlattices or in supracrystals (3D) are pointed Out. These properties are either due to dipolar interactions with the appearance Of Coupled plasmon modes or to the attraction between nanocrystals, self-assembled via interdigitation of the alkylchains used as coating agents, which leads to coherent vibrations of nanocrystals in a supracrystal.