Much progress has been made over the past ten years on the synthesis of monodisperse spherical nanocrystals. Mechanistic studies have shown that monodisperse nanocrystals are produced when the burst of nucleation that enables separation of the nucleation and growth processes is combined with the subsequent diffusion-controlled growth process through which the crystal size is determined. Several chemical methods have been used to synthesize uniform nanocrystals of metals, metal oxides, and metal chalcogenides. Monodisperse nanocrystals of CdSe, Co, and other materials have been generated in surfactant solution by nucleation induced at high temperature, and subsequent aging and size selection. Monodisperse nanocrystals of many metals and metal oxides, including magnetic ferrites, have been synthesized directly by thermal decomposition of metal-surfactant complexes prepared from the metal precursors and surfactants. Nonhydrolytic sol-gel reactions have been used to synthesize various transition-metal-oxide nanocrystals. Monodisperse gold nanocrystals have been obtained from polydisperse samples by digestive-ripening processes. Uniform-sized nanocrystals of gold, silver, platinum, and palladium have been synthesized by polyol processes in which metal salts are reduced by alcohols in the presence of appropriate surfactants.

We synthesized Ni/Pd core/shell nanoparticles from the consecutive thermal decomposition of metal-surfactant complexes. The nanoparticle catalyst was atom-economically applied for various Sonogashira coupling reactions.

We have synthesized monodisperse Pd nanoparticles with particle sizes of 3.5, 5, and 7 nm from the thermal decomposition of a Pd− surfactant complex. The particle size of Pd nanoparticles was controlled by varying the concentration of stabilizing surfactant.The development of uniform nanometer sized particles has been intensively pursued because of the many technological and fundamental scientific interests associated with these nanoparticles. 1 These nanoparticular materials often exhibit very interesting electronic, optical, magnetic, and chemical properties, which are unachievable for their bulk counterparts. 2 They have a characteristic high surface-to-volume ratio, and consequently a large fraction of the metal atoms are at the surface, and hence are available for catalysis. Many colloidal nanoparticles of transition metals have been synthesized and applied as catalysts for organic reactions. 3 Recently, the synthesis of uniform sized (or monodisperse) nanoparticles became a very important research area. 4 Klabunde and co-workers synthesized highly monodisperse gold nanoparticles from the digestive ripening, which employed aging of polydisperse nanoparticles in the presence of excess surfactant. 5 Even though there are many reports on the synthesis of Pd nanoparticles, there is virtually no report on monodisperse Pd nanoparticles. 6 Here, we report on the synthesis of monodisperse Pd nanoparticles from the thermal decomposition of Pd-surfactant complexes.The current synthetic procedure is a modified version of the method developed by our group for the synthesis of monodisperse nanocrystals of metal oxides, and which employs the formation of a metal-surfactant complex followed by aging at high temperature. 7 In the synthesis, Pd-surfactant complex, which was prepared at room temperature, was slowly heated to a high temperature, followed by aging at that temperature. The following describes the detailed synthetic procedure for monodisperse 3.5 nm Pd nanoparticles.