Phase-Segregation Control and Unique Properties of Inorganic Nanoparticles

Since the primary structures of inorganic nanoparticles, such as size and shape, determine their physical and chemical properties, the control of such structures is prerequisite for both the elucidation of structure-dependent properties and the direct assembly of hierarchical structures. When a nanoparticle consists of two distinct chemical species, the distribution of chemical species becomes another determinant for its properties and functions. In general, this chemical synthesis provides us with chemically-disordered alloys or core-shell structures, in which two distinct chemical species isotropically distribute. Recently, anisotropically phase-segregated nanoparticles have been accessible and received much attention due to two important features: First, one can simultaneously utilize two different functions, such as the luminescent and magnetic properties. Second, two distinct functional ligands can be anisotropically arranged at the surface of these particles, thus leading to a directed assembly of micro- and nanostructures. Third important feature of anisotropically phase-segregated nanoparticles is that the atom, ion, and charge transfers can occur at the interface between two inorganic phases.





Discoverty of Anisotropically Phase-Segregated CoPd Sulfide (Co9S8/PdSx) Nanoacorns



HRTEM images and crystal structure of CoPd sulfide (Co9S8/PdSx) nanoacorns.

[Ref.] JACS 2004, 126, 9915.; Chem. Lett. 2007, 36, 490.


Synthesis of PdCoPd Sulfide (PdSx/Co9S8/PdSx) Nanopeanuts
Formed by Fusing Two CoPd Sulfide Nanoacorns



PdCoPd sulfide nanopeanuts formed by the seed-mediated growth of PdSx seed.



Selective formation of nanopeanuts and nanoacorns by changing the amount of C18SH.

[Ref.] Angew. Chem. Int. Ed. 2007, 46, 1713.


Synthesis of Anisotropically Phase-Segregated Pd/γ-Fe2O3 Nanoparticles



(a)TEM image and (b)HRTEM image of anisotropically phase-segregated Pd/γ-Fe2O3 nanoparticles

[Ref.] JACS 2008, 130, 4210.