Precipitation of spherical and 'fiber-like' silver particles

Silver nanoparticles with various sizes and shapes were prepared by adding silver nitrate to ascorbic acid solutions containing nitric acid and a dispersant (Daxad 11G). It is shown that the reaction environment significantly affects the nature of the interactions between silver ions and dispersant molecules. The stability of the Ag(+)/Daxad 11G intermediate species formed, which determines the reduction rate and, implicitly, the particle size and shape, is strongly affected by the dispersant/Ag(+) ratio and the concentration of nitric acid. Uniform highly dispersed Ag nanoparticles were obtained at high concentrations of HNO3, while lower acid concentrations favored the formation of 'fiber-like' metallic structures. The propensity for forming anisotropic silver structures is attributed to the planar structure and chromonic properties of dispersant molecules.