A Study of Electrolytic Coagulation of Gold Sols by the Method of Localized Surface Plasmon Resonance Spectroscopy

摘要

Surface plasmon resonance spectroscopy has been employed to study the aggregation of gold sols with average nanoparticle sizes of 15-35 nm under the action of an indifferent electrolyte (NaCl). The struc- ture of resulting aggregates has been established as depending on the coagulation regime. In the regime of fast coagulation, anisotropic aggregates with branched structure are initially formed; then, they are transformed into denser aggregates with a lower degree of anisotropy. The change of the aggregate structure accelerates with an increase in hydrosol concentration. At the same time, slow coagulation obviously yields denser aggre- gates, the structure of which is independent of the sol concentration and particle size. A procedure has been proposed for estimating the critical coagulation concentration of gold hydrosols based on the analysis of vari- ations in their extinction. It has been found that the critical coagulation concentration increases with a reduc- tion in the sol concentration and gold nanoparticle size.