Formation of Stable Ag-Nanoparticle Aggregates Induced by Dithiol Cross-Linking

Aggregation of thiol-stabilized silver nanoparticles induced by 1,6-hexane dithiol was studied in situ by dynamic light scattering. The aggregates were observed to reach a finite size in the 100−200 nm range depending on the applied conditions. Growth kinetics were shown to be linked to the dynamics of the thiol-exchange reaction. A model for the aggregation process was developed on the basis of a simple diffusion-kinetic approach assuming an elementary kinetic reaction at the surfaces and a spherical diffusion field surrounding the aggregates. The rate constant for the thiol exchange reaction was found to vary between 0.6 and 4.0 × 10-4 s-1, and the activation energy was 46 ± 10 kJ mol-1.