Seed mediated growth: A convenient way for size control in nanoparticle synthesis

Preparation of monodispersed metal nanoparticles of different sizes has much importance in nanotechnology. The size-controlled synthesis of nanoparticles is carried out either by using the capping property of a stabilizer that restricts the particle growth at the intermediate stage or by exploiting the variable size of the water pool of a reverse micelle as template. We herein report a convenient and general (i. e., seed mediated) method of preparation of metal nanoparticles of controlled size in which small particles are prepared (as seeds) with relatively stronger reducing agents followed by preparation of bigger particles on the seeds by reducing the metal ions with weaker reductants. By this procedure, metal particles of Cu, Ag, Au and Pd of different sizes (10-200nm) have been synthesized, characterized and the role of the reducing power of the reductants has been discussed.