POTENTIOMETRIC STUDY OF KINETICS AND MECHANISM FORMATION OF SILVER NANOPARTICLES STABILIZED BY SYNTHETIC FULVATES

Silver nanoparticles are actively studied due to their unique properties and wide use in various fields. In this study, silver nanoparticles were obtained by reacting Ag+ ions with synthetic fulvic acids derived from quercetin. Synthetic fulvic acids perform a dual function: a reducer of silver ions and a stabilizer of the formed nanoparticles The presence of silver nanoparticles in the solution is confirmed by the presence of a maximum in the absorption spectrum at 400 nm, which is due to the phenomenon of surface plasmon resonance. The parameters of the crystal lattice were established using the X‑ray diffraction method. The average nanoparticle size calculated by the Scherrer formula is 28 nm. The kinetics and mechanism formation of silver nanoparticles were studied by potentiometry, which allows direct and continuous control of the consumption of silver ions in the synthesis process. It is established that the mechanism of the process depends on the pH of the medium. In particular, at high pH values of the reaction medium there is a heterogeneous mechanism, while at low – homogeneous. The heterogeneous mechanism of formation of silver nanoparticles is characterized by the presence of three stages, in particular: 1) formation of Ag2O microparticles after mixing reagents, 2) reduction of Ag+ ions by synthetic fulvic acids from quercetin on the surface of formed Ag2O microparticles, which are heterogeneous nucleation centers. 3) reduction of Ag+ ions from solution on the surface of silver nanoparticles after complete dissolution of Ag2O microparticles (this process is described by first-order kinetics by Ag+). Activation parameters for different stages of silver nanoparticle formation using quercetin fulvic acids were calculated. A potentiometric study of the influence of the degree of aeration of the medium on the kinetics of changes in the pAg system was performed.