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Cation Exchange:  A Simple and Versatile Route to Inorganic Colloidal Spheres with the Same Size but Different Compositions and Properties

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posted on 13.03.2007, 00:00 by Pedro H. C. Camargo, Young Hwan Lee, Unyong Jeong, Zhiqing Zou, Younan Xia
This paper describes a cation exchange approach to the synthesis of metal chalcogenide core−shell particles with the same size but a number of different compositions. This method begins with the preparation of colloidal spheres of amorphous Se (a-Se), followed by their reaction with Ag atoms to form Se@Ag2Se spheres. These core−shell spheres are then converted into Se@MSe (M = Zn, Cd, and Pb) via cation exchange with Zn2+, Cd2+, and Pb2+. All the colloidal spheres prepared using this method are monodispersed in size and characterized by a spherical shape and a smooth surface. Starting from the same batch of Se@Ag2Se, the resultant Se@MSe samples were essentially the same in size. Furthermore, these core−shell colloidal spheres can be easily made superparamagnetic by incorporating Fe3O4 nanoparticles into the a-Se cores. This synthetic approach provides a simple and versatile route to magnetoactive core−shell spheres with the same size but a range of different compositions. This study also implies that it is feasible to further increase the diversity of cations that can be used in the cation exchange of a colloidal system to produce multifunctional core−shell spheres with a variety of properties.