Soft Chemistry Routes to New Nanosize Materials

Abstract

The old classical method for preparing inorganic materials is by the ceramic route or solid state reaction. It consists of mixing the starting materials at an elevated temperature. This method has been used for preparing numerous new materials until today. Three decades ago, the materials science community was aware of soft chemistry synthesis or chimie douce, especially with the emergence of nanotechnology field. Instead of the classical method, which involves high temperature, soft chemistry techniques use lower temperatures. In general, starting materials are dissolved in a liquid phase and different parameters such as pH, temperature and reaction time are adjusted in order to obtain the desired product. By using a lower temperature of preparation, the product obtained shows nanosize particles, with sizes lower than 100 nanometers. In contrast, the ceramic route (or solid state reaction) using higher temperatures leads to bigger particles size that are out of the nanosize range. Also, some interesting phases that are not stable at elevated temperatures (named metastable phases) and are not accessible by the classical method, are now prepared by the soft chemistry technique. Usually these metastable phases have interesting structural features and important physical properties. Adding to that, the product is obtained with a higher level of purity.