Large triangular single crystals formed by mild annealing of self-organized silver nanocrystals.

Nanocrystal organizations represent a new generation of materials with specific properties compared with those of isolated nanocrystals and of the bulk material. Here, we present the first intrinsic crystalline growth properties of highly ordered mono- and multilayers of 5 nm silver nanocrystals. Triangular single crystals with face-centred-cubic structures are obtained by annealing the ordered nanocrystals under atmospheric pressure at 50 degrees C. The triangles are mixed with well-crystallized coalesced particles of various shapes. Their size depends on the initial nanocrystal ordering range on the substrate, which is local on amorphous carbon and highly extended on highly oriented pyrolitic graphite (HOPG). Hence, the single-crystal size is larger on HOPG than on amorphous carbon. These observations show that the crystalline growth properties of silver nanocrystals can be tailored by controlling their organization. Furthermore, on HOPG an epitaxial orientation of the triangles is observed.