TABLE OF CONTENTS Several procedures have been used to obtain particles with sizes in the 1 50 nanometer scale through chemical reactions. Those procedures vary from simple precipitations to chemical reductions, including hydrolisis processes, thermal decompositions, etc. For example a procedure for obtaining amorphous NdFeB magnetic nanoparticles [1] consists of the reduction of Fe 2+ and Nd 3+ salts using borohydride ions in aqueous solution. The concentration and speed of addition of the reactants, the control of the pH, the temperature and the atmosphere under which the reaction is carried out are parameters affecting the characteristics of the particles obtained. In order to control the growth of the particles and fix their size so as to obtain a quasi-monodisperse distribution of particles, procedures have been developed based on carrying out the reaction in a microstructured medium. The use of microemulsions is particularly convenient because the system is thermodynamically stable and easy to reproduce, and the size of the microreactor (microdroplets) can be easily controlled. Semiconductor and metallic nanoparticles can be produced by injecting molecular precursors into a hot surfactant solution [2]. For instance, monodisperse cobalt nanoparticles are formed by the thermal decomposition of carbonyl dicobalt, Co 2(CO) 8. This decomposes according to the reaction Co 2(CO) 8 ? 2Co + 8 CO, and an appropriate combination of surfactants and stabilizing ligands controls the growth and stabilizes the particles, also preventing their oxidation [3].
Gold...
