Kytsya A. Kinetics of the formation of Ag-, Cu- and Ni-containing nanoparticles in solutions

The dissertation is devoted to the investigation of kinetics and thermodynamics of the formation of mono- and bimetallic nanoparticles with the aim of establishing the mechanisms of their formation. Based on the comparison of the results of a complex experimental study of the kinetics of the formation of silver, copper and nickel nanoparticles in solutions under the conditions of their homogeneous nucleation, a comparative analysis of the possibility of using different versions of pseudo-homogeneous Finke-Watzky kinetic schemes to describe the processes of particle nucleation, growth and aggregation was carried out. The correlations between the observaleble rate constants of nucleation, growth, and aggregation and the polydispersity of the obtained nanoparticles were revealed. Based on the comparison of the activation parameters of nucleation and growth of nanoparticles with the redox potentials of the corresponding metals it is shown that the nucleation of a new phase is limited by the chemical process of reduction of metal ions. The molecular modeling of the elementary stages of Ag4 cluster formation was carried out and it was established that the thermodynamic probability of stepwise formation of a critical nucleus of silver by the joining a silver ion to a growing uncharged cluster with subsequent reduction of the polyatomic cation Agn+ is higher compared to the association of uncharged Ag0 atoms. A kinetic model of the formation of metal nanoparticles under the conditions of their homogeneous nucleation is proposed and the equations for calculation the concentration of the formed particles and their sizes are derived. Based on a detailed analysis of the kinetics of Ag+ reduction by hydrazine in aqueous solutions the mechanism of growth of AgNPs is proposed and the rate constants of the elementary stages of the process are calculated. The kinetics of the formation of nickel nanoparticles by the reduction of Ni(OH)2 with hydrazine in ethylene glycol solutions was investigated and the mechanism of the formation of NiNPs in heterogeneous systems was proposed. The kinetics of the formation of Ni-Co bimetallic nanoparticles was studied and it was shown that the rate of nucleation of Ni-Co-NPs is determined by the concentration of Ni(OH)2, and the rate of growth is determined by the concentration of Co(OH)2. The kinetics of cementation of silver ions on the surface of NiNPs was investigated and a kinetic model of the process was proposed. It has been established that mono- and bimetallic nanoparticles based on nickel are capable of electrochemical hydrogenation and exhibit significant discharge capacity. The catalytic activity of Ni-Co-NPs in the process of hydrogen generation by hydrolysis of NaBH4 was shown. The antimicrobial activity of AgNPs was studied. The pro¬mising application of mono- and bimetallic nanosystems as additives to the lubricants is shown.