Effect of a side reaction involving structural changes of the surfactants on the shape control of cobalt nanoparticles.
Cobalt nanoparticles with different sizes and morphologies including spheres, rods, disks, and hexagonal prisms have been synthesized through the decomposition of the olefinic precursor [Co(η(3)-C8H13)(η(4)-C8H12)] under dihydrogen, in the presence of hexadecylamine and different rhodamine derivatives, or aromatic carboxylic acids. UV-vis spectroscopy, X-ray diffraction, low and high resolution transmission electron microscopy, and electron tomography have been used to characterize the nanomaterials. Especially, the Co nanodisks formed present characteristics that make them ideal nanocrystals for applications such as magnetic data storage. Focusing on their growth process, we have evidenced that a reaction between hexadecylamine and rhodamine B occurs during the formation of these Co nanodisks. This reaction limits the amount of free acid and amine, usually at the origin of the formation of single crystal Co rods and wires, in the growth medium of the nanocrystals. As a consequence, a growth mechanism based on the structure of the preformed seeds rather than oriented attachment or template assisted growth is postulated to explain the formation of the nanodisks.
Laboratoire de Chimie de Coordination, CNRS , 205 route de Narbonne, F-31077 Toulouse, France.
Miguel
M
Comesaña-Hermo
Robert
R
Estivill
Diana
D
Ciuculescu
Zi-An
ZA
Li
Marina
M
Spasova
Michael
M
Farle
Catherine
C
Amiens