Synthesis of cobalt nanoparticles in aqueous solutions assisted by polymer/inorganic hybrid

Abstract

Hydrophilic polymer/inorganic hybrids (PIH) containing silica nanoparticles and polyacrylamide chains proved to be effective matrices for the in situ synthesis of cobalt nanoparticles. PIH sample was synthesized by free-radical polymerization of acrylamide from the unmodified surface of SiO2 nanoparticles and characterized by elemental analysis, dynamic thermogravimetric analysis, static light scattering, potentiometric titration, viscometry and transmission electron microscopy (TEM). The processes of borohydride reduction of cobalt ions from the Co(NO3)2·6H2O solution to nanoparticles in water medium and aqueous solutions of PIH were studied as a function of the concentrations of metal salt and hybrid concentrations using UV-Vis spectroscopy and TEM. A special approach to characterize the kinetics and efficiency of CoNPs formation in water medium and hybrid solutions using UV-Vis spectroscopy was implemented. The kinetic parameters of the CoNPs formation process as well as the yield, size, and morphology of nanoparticles in hybrid solutions and water medium at various concentrations of metal salt and hybrid were determined. The growth of both concentrations of reagents had a positive effect on the rate of formation of metal nanoparticles and their yield, but in all cases, the reduction process developed much slower in hybrid solutions compared to pure water. The morphology of the CoNPs/PIH nanocomposites was mainly represented by separate swollen hybrid particles containing metal nanoparticles with dav~3 nm.