Abstract

The present work shows the synthesis of Ag nanoparticles in a two-phase system (organic/aqueous), in which the amphiphilic properties of naphthenic acid are used for the formation of reverse micelles that act as micro reactors. Therefore, the appropriate energy conditions are given for the precipitation of metallic Ag nanoparticles, using AgNO3 as a precursor. Likewise, the effect of the synthesis reaction time was studied to know its relationship with the final morphology of the material. X-Ray Diffraction and Scanning Electron Microscopy, coupled with Energy Dispersive Spectroscopy, were used to characterize the solids. The results show that in the Ag+ -> Ag° reduction reaction carried out at t = 1.5 h and T = 200 °C, metallic silver nanoparticles precipitate of FCC structure, with homogeneous globular morphology and average diameter of 50 nm. By prolonging the residence time of the system at 200 °C (artificial aging), the material undergoes a series of transformations both in size and morphology, causing partial oxidation of the silver. At TEA of 0.5 h, the particles grow without evident structural change; by increasing TEA to 1 h, the transformation in solid state is observed, obtaining a mixture of phases, AgO, Ag3O4 and Ag2O, coming from the partial oxidation of silver, with monoclinic and hexagonal structures and the dimensions nano and micrometric. Finally, increasing the aging time to 1.5 h only causes an increase in particle size, without modification in the structures obtained at shorter times.