元素置換による未踏構造ナノ結晶の創製

抄録

Elaborate chemical synthesis methods allow the production of various types of inorganic nanocrystals (NCs) with uniform shape and size distributions. The transformation of already-synthesized NCs via elemental substitutions can overcome the difficulties facing conventional one-step syntheses. As for ion exchange reactions, the cation exchange reactions proceed much faster than the anion exchange reactions because anions generally have much larger ionic radii than cations within the frameworks of NCs. For ionic NCs above a critical size, the anion framework generally remains intact, and the original shape of the parent NCs is retained throughout the cation exchange reaction. As a special case, we show that thermodynamic instability of exposed planes drives reconstruction of anion frameworks under mild reaction conditions. In contrast, the anion exchange reaction often provides the new NCs with unique structures, such as hollow or anisotropically phase-segregated assemblies. Then, we experimentally show the first example of an unprecedented pseudo-binary Z3-FePd₃ alloy NCs by adding a small amount of In, which is immiscible with Fe but miscible with Pd. Finally, a general outline of the transformation of NCs via element substitution reactions and future prospects in this field are provided.