Plasmochemical preparation of silver nanoparticles: thermodynamics and kinetics analysis of the process

Abstract

The thermodynamics and kinetics analysis of the plasmochemical formation of silver nanoparticles is performed. The thermodynamics analysis is made on the basis of calculation of the Gibbs free energy of formation of silver nanoparticles in an aqueous medium by various methods. It was found that the Gibbs free energy in aqueous solutions increases with decreasing size of silver particles. Based on experimental data, it was determined that the average size of plasmochemically prepared particles depends on the initial concentration of silver ions in the solution and equals 36.5–60.1 nm for 0.25–3.0 mmol/l. The kinetics of chemical conversion in aqueous solutions of silver nitrate under plasma treatment conditions in a gas-liquid plasmochemical batch reactor is investigated. The curves of Ag + dependence on duration of plasmochemical treatment of solutions and initial concentration of silver ions are given. It is found that the process of plasmochemical formation of silver nanoparticles is the second-order reaction. The rate constant of formation of silver nanoparticles is k=0.07–1.53 mol -1 ∙dm 3 ∙min -1 depending on the initial concentration of silver ions. It is shown that the formation of silver nanodispersions under plasma discharge impact is characterized by the presence of the peak λ max =400–440 nm.