Study of Nucleation and Growth in the Organometallic Synthesis of Magnetic Alloy Nanocrystals:  The Role of Nucleation Rate in Size Control of CoPt₃ Nanocrystals

Abstract

High quality CoPt(3) nanocrystals were synthesized via simultaneous reduction of platinum acetylacetonate and thermodecomposition of cobalt carbonyl in the presence of 1-adamantanecarboxylic acid and hexadecylamine as stabilizing agents. The high flexibility and reproducibility of the synthesis allows us to consider CoPt(3) nanocrystals as a model system for the hot organometallic synthesis of metal nanoparticles. Different experimental conditions (reaction temperature, concentration of stabilizing agents, ratio between cobalt and platinum precursors, etc.) have been investigated to reveal the processes governing the formation of the metal alloy nanocrystals. It was found that CoPt(3) nanocrystals nucleate and grow up to their final size at an early stage of the synthesis with no Ostwald ripening observed upon further heating. In this case, the nanocrystal size can be controlled only via proper balance between the rates for nucleation and for growth from the molecular precursors. Thus, the size of CoPt(3) nanocrystals can be precisely tuned from approximately 3 nm up to approximately 18 nm in a predictable and reproducible way. The mechanism of homogeneous nucleation, evolution of the nanocrystal ensemble in the absence of Ostwald ripening, nanocrystal faceting, and size-dependent magnetic properties are investigated and discussed on the example of CoPt(3) magnetic alloy nanocrystals. The developed approach was found to be applicable to other systems, e.g., FePt and CoPd(2) magnetic alloy nanocrystals.

One-pot aqueous synthesis of highly strained CdTe/CdS/ZnS nanocrystals and their interactions with cells

“…At the early stage of particle growth, the usage of a very low Te-to-Cd molar ratio resulted in the formation of a small population of small particles. 20 In this case, depletion of free monomers proceeded slower than in the case of higher Te-to-Cd ratios. The extended depletion time of monomers avoided the Oswald ripening process, a process which originated from a slow-growth rate, resulting in a broadening of size distributions.…”

Nanostructured Pt-alloy electrocatalysts for PEM fuel cell oxygen reduction reaction

“…Some special nanoparticle shapes, such as cubic, truncated cubic and plate-like, can also be formed. 15,16,37,85 By extending the dimension of nanoparticles in a desired direction, some well-defined, so-called one-dimensional nanostructures such as nanotubes, nanowires, nanobelts, nanoneedles and nanorods have been synthesized, and these exhibit enhanced ORR catalytic activity and selectivity. 15,28 Apparently, we need systematic studies of controlling parameters in the synthetic routes of Pt nanostructures with different shapes-such as spheres, wires, rods, whiskers and tubes-for application in electrochemical energy devices.…”

Metal nanoparticle field-effect transistor

“…Today, the control over nucleation and growth phases of nanocrystals allows tayloring the crystal size, while the amount and nature of ligand molecules and precursors permits control over shape, surface properties, and atomic composition of the nanocrystals [34]. In some systems it is possible to synthesize such structures with almost atomic precision and in macroscopic amounts [35,36]. The colloidal synthesis of nanocrystals is comparatively fast, inexpensive, and scalable.…”