Colloidal metallic nanoparticles have unique optical, electrical, magnetic and thermal properties and many applications such as biosensors, high-density recording medias, magnetic fluids, drug deliveries and gene therapies. The physical and chemical properties of colloidal nanoparticles are dependent not only on the materials system but also on their size and shape. Therefore, monodispersed nanoparticles with controlled shape are required for many applications of colloidal nanoparticles.
In order to fabricate monodispersed metallic nanoparticles, several chemical processes were proposed during the last decade. Among them, polyol process has been employed for the synthesis of colloidal metallic and bimetallic nanoparticles. In the polyol process, the polyol (two or more $OH^-$) acts as reducing agent, solvent and stabilizer, simultaneously. Recently, the polyol process has been modified for the synthesis of noble metal seeds or nuclei prior to the coating of another metallic material that does not nucleate homogeneously. However, the polyol process is a relatively slow reaction process compared to the thermal decomposition process. It, usually, takes several hours for nucleation and growth of nanoparticles without any additives. Although it is not beneficial to use the polyol process for synthesis of the monodispersed nanoparticles, it provides many opportunities to change and control the particle size and shape during the process. So far, only the ethylene glycol and PVP (polyvinylpirrolidone) have been used for the typical polyol process and there have been few attempts to modify it.
In this study, the polyol process was modified, i.e., the octylether, which is long chain polyol (1,2-hexadecanediol), and long alkyl chain surfactants were used as solvent, reducing agent and stabilizer, respectively. By using the modified polyol process, the relationship between process parameters and size and shape of colloidal metallic nanoparticles were investigated.