Chemistry of reverse micelles: a versatile route to the synthesis of nanorods and nanoparticles

Abstract

Nanostructured wires and rods are expected to have interesting optical, electrical, magnetic and mechanical properties as compared to micron sized whiskers and fibers. We have explored a versatile route for the synthesis of nanorods of transition metal (Cu, Ni, Mn, Zn, Co and Fe) oxalates, succinates of few metals (Co and Fe) and SnO2 nanoparticles using reverse micelles. The aspect ratio of the nanorods copper oxalate could be modified by changing the solvent. The aspect ratio of the cobalt oxalate nanorods could be modified by controlling the temperature. The nanorods of metal (Cu, Ni, Mn, Zn, Co and Fe) oxalates were found to be suitable precursors to obtain a variety of transition metal oxide nanoparticles. Our studies show that the grain size of CuO nanoparticles is highly dependent on the nature of non-polar solvent used to initially synthesize the oxalate rods. All the commonly known manganese oxides could be obtained as single phases from the manganese oxalate precursor by decomposing in different atmosphere (air, vaccum or nitrogen). In order to see the templating effect of the ligand we have changed the dicarboxylate ligand by using succinate (4 carbon chain) instead of oxalate (2 carbon chain).We found spherical nanoparticles for iron succinate where the oxidation state of Fe is in +3. Shorter rods of cobalt succinate were observed. Monophasic tin dioxide (SnO2) nanoparticles with an average size of 6-8 nm was obtained at 500°C by the reverse micellar route using liquor NH3 as precipitating agent.