Vadim Palshin

Synthesis of poly(methyl methacrylate) stabilized colloidal zero-valence metallic nanoparticles

Poly(methyl methacrylate) (PMMA) stabilized colloidal metallic iron nanoparticles without additional surfactant or stabilizer were fabricated by a wet chemical reduction method. The synthesized colloidal iron nanoparticles were found to be stable in tetrahydrofuran (THF) solution and the dried PMMA–Fe nanocomposites were ferromagnetic even at room temperature as illustrated by magnetometer measurement. The particle size increased with the decrease of the initial PMMA concentration and the magnetic properties also depended on the initial PMMA concentration.

A new role for surfactants in the formation of cobalt nanoparticles

During wet-chemical synthesis of nanoparticles it is believed that surfactants interact with the particles after their nucleation thereby controlling their crystal structure, shape and size. Contrary to this, our investigations presented in this paper reveal a new role for surfactants: influencing the reaction pathways, prior to nucleation, leading to the formation of cobalt nanoparticles. The results from the mechanistic investigation of the influence of various surfactants on the formation of cobalt nanoparticles carried out using time dependent FT-IR spectroscopy support this observation. The utilization of different surfactants such as oleic acid (OA), trioctylphosphine oxide (TOPO), octadecylamine (ODA), and trioctylphosphine (TOP) led to differences in reaction pathways and reaction intermediates, prior to the nucleation, leading to the formation of Co nanoparticles with very different properties. The particle size and size distribution were obtained from transmission electron microscopy (TEM). The electronic and geometric properties of the cobalt nanoparticles obtained were determined using synchrotron radiation based X-ray absorption spectroscopy (XAS) and the magnetic properties were measured using SQUID magnetometry.

Effect of Precursor on the Electronic and Geometric Properties of Cobalt Nanoparticles Investigated by Co‐K XANES and EXAFS

By varying techniques and parameters in wet‐chemical synthesis Co‐nanoparticles different crystallographic structures (hcp, fcc and epsilon) can be synthesized. Co‐K XANES and EXAFS spectra are very powerful tools to distinguish between those structures. In this study we are investigating for the first time the effect of the precursor molecule used for the synthesis on the electronic and geometric properties of cobalt nanoparticles. As precursors two organometallic cobalt complexes were used: alkyne‐bridged dicobalthexacarbonyl [(Co2(μ‐HC≡CH)(CO)6] (ADH) and the well known dicobalt octacarbonyl [Co2(CO)8] (DCO). Both precursors were thermally decomposed under identical reaction conditions. Besides, effect of the precursor on the Co NPs was also investigated when two different types of surfactants are utilized in the reaction, oleic acid and n‐trioctylphosphine. When only oleic acid was used as the surfactant, the XAFS analysis showed formation of fcc structure with ADH and hcp with DCO. When a combination...