Litvin V. Synthesis and properties silver and gold nanoparticles stabilized by synthetic humic substances

The thesis is devoted to the research of physico-chemical processes of obtaining of silver and gold nanoparticles with use synthetic humic substances (HSs) and to complex study of their properties. The new techniques of preparation of synthetic fulvo- and humic acids are developed and the basic physico-chemical properties of the received products are investigated. The advantage of synthetic HSs over natural materials is their reproducible and controllable properties. Synthetic humic substances was used in role of reducers and stabilizers in synthesis of silver and gold nanoparticles. The reaction conditions were optimized to achieve a 99,99% yield and long-term aggregate stability of sols (over 1 year). It is found that varying the synthesis conditions, the controlled size (within 8-60 nm) and shape (spherical, rods-like) of nanoparticles can be obtained. The basic physico-chemical properties of received nanoparticles are investigated. On the basis of experimental data and quantum-chemical calculations the schemes of formation of silver and gold nanoparticles stabilised by synthetic humic substances are offered. It is established that the mechanism of silver nanoparticles formation depends on the concentration of alkali in the reaction medium: at high pH values the formation of silver nanoparticles occurs according to heterogeneous mechanism and at low pH - according to homogeneous mechanism. The kinetic and thermodynamic characteristics of processes are calculated. The strengthened antibacterial properties of the received silver and gold nanoparticles on the basis of synthetic humic substances are proved.