Search

Thecontrol of the metallic nanocrystal shape is of prime importancefor a wide variety of applications. We report a detailed researchwork on metal–organic chemical routes for the synthesis ofa highly symmetrical crystal structure. In particular, this studyshows the key parameters ensuring the anisotropic growth of nickelnanostructures (fcc crystal). Numerous reaction conditions are investigated(precursors, solvents, temperature, reducing agents, reaction time,and types and ratios of surfactants, such as alkyl amines, carboxylicacids, and phosphine oxides), and their effects on the size and shapeof the final product are reported. The role of the growth modifiersand the structuring of the reaction media on the anisotropic growthare demonstrated. This metal–organic approach generates severalnovel anisotropic nanostructures in a wide size range depending onthe reaction conditions. In this way, nanomaterials with reproduciblesize, shape, and composition are obtained with good yield. Transmissionelectron microscopy techniques (TEM and HRTEM) are the principal methodsfor monitoring the morphology. [ABSTRACT FROM AUTHOR]

Cobalt nanoparticles with differentsizes and morphologies includingspheres, rods, disks, and hexagonal prisms have been synthesized throughthe decomposition of the olefinic precursor [Co(η3-C8H13)(η4-C8H12)] under dihydrogen, in the presence of hexadecylamine anddifferent rhodamine derivatives, or aromatic carboxylic acids. UV–visspectroscopy, X-ray diffraction, low and high resolution transmissionelectron microscopy, and electron tomography have been used to characterizethe nanomaterials. Especially, the Co nanodisks formed present characteristicsthat make them ideal nanocrystals for applications such as magneticdata storage. Focusing on their growth process, we have evidencedthat a reaction between hexadecylamine and rhodamine B occurs duringthe formation of these Co nanodisks. This reaction limits the amountof free acid and amine, usually at the origin of the formation ofsingle crystal Co rods and wires, in the growth medium of the nanocrystals.As a consequence, a growth mechanism based on the structure of thepreformed seeds rather than oriented attachment or template assistedgrowth is postulated to explain the formation of the nanodisks. [ABSTRACT FROM AUTHOR]