Designed synthesis of cobalt and its alloys by polyol process

The role of polyol, precursor and reaction promoting agents in the synthesis of metal and alloy nanoparticles using polyol process has been investigated by analyzing the reaction steps involved in the synthesis of cobalt in Co ion-polyol-[OH-] ion system in detail. The reducing potential of polyols and the easiness with which any metal salt can react to form reducible complexes has been evaluated using the orbital molecular theory and the results were experimentally verified. The reduction limit of polyol and their extension using reaction promoting agents such as [OH-] ions is also explained. The reduction of cobalt is preceded by various reaction stages of complex/compound formation, which has been fully identified. Furthermore, the reducing form of cobalt has been identified as either cobalt alkoxide or cobalt hydroxide. The results confirmed that the complex forming reactions that take place prior to the formation of the precursor, which finally get reduced to metal, play a decisive role in determining the physical properties of the nanoparticles. The approach can be extended to reduce any metals or alloys using polyol process. (C) 2007 Elsevier Inc. All rights reserved.