Nanoparticles from compounds with layered structures

Layered structures of the type B8, C6, and C7 excel in the fact that the binding within the layers between the metal and the non-metal is of the covalent type and between the layers of the van der Waals type. This leads, in the case of nanoparticles, to a large number of dangling bonds on the periphery of the layers. In the well-studied case of graphite, the formation of onion-like structures and nanotubes reduces the free energy of the system, it is shown that the formation of these morphologies is very general for small particles. This is shown for BN, MoS2, WS2, WSe2, and MoSe2. SnS2 and ZrSe2 are special exceptions, as nanoparticles of these compounds preferably form rope-like structures. These experiments lead to the general rule that nanoparticles made of layered compounds try to form closed structures. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.