Kinetic and mechanism formation of silver nanoparticles coated by synthetic humic substances

In this work, we demonstrate efficiency of the usage of synthetic humic substances (HSs) as reducing and stabilizing agent in preparation of silver nanoparticles for the first time. Preference of synthetic HSs over natural HSs is determined by a standardization problem resolution due to the strict control of conditions of the HS formation that expands the areas of application of the silver nanoparticles made on their basis. The formation of silver nanoparticles is confirmed by the UV–vis spectroscopy, X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The potentiometric and spectrophotometric data of kinetic study of the silver nanoparticles formation are reported. On the basis of various observations, a three-stage of silver nanoparticles formation is proposed: a fast formation of the Ag2O microphase in system after mixing of reagents; reduction of silver ions on the surface of Ag2O particles according to the zero-order kinetics; growth of silver nanoparticles due to reduction of silver ions from a solution on a surface of already generated nucleus of silver nanoparticles according to the first order kinetics after the Ag2O microphase dissolution.

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► The silver nanoparticles have been obtained using synthetic humic substances as reducing and capping agent.
► The advantage of synthetic humic substances over natural analogous is represented by the controlled and reproducible properties.
► Kinetics of silver nanoparticles formation have been studied by potentiometric and spectrophotometric methods.
► The three stages of the silver nanoparticles formation are detected.