Effect of Surfactant Concentration and Aggregation on the Growth Kinetics of Nickel Nanoparticles

The effect of trioctylphosphine (TOP) concentration on the growth of nickel nanoparticles is studied using in situ synchrotron small-angle X-ray scattering. The growth kinetics are fitted using a two-step nucleation and autocatalytic growth model. TOP acts as a nucleating agent and then acts as an inhibitor against rapid particle growth. Increasing the TOP concentration results in smaller nanoparticles. Once there is a critical concentration of nickel particles above a certain size, they start to aggregate. This results in a broadening of the particle size distribution at later times due to particles on the outside of the aggregates continuing to grow, while those on the inside cease to grow as the nickel precursor is locally depleted.