We use dynamic light scattering to characterize the kinetics of nanoparticle aggregation. The aggregation process was conveniently initiated in photoacid generator (PAG) solutions where changes in the pH of the solution can be controlled by exposure to ultraviolet light without the delays from mixing or stirring. The nanoparticle aggregation kinetics is extremely sensitive to the solution pH and we find that the UV exposure dose is inversely correlated to the surface charge of the nanoparticles, effectively decreasing the electrostatic repulsion force between particles leading to aggregation. The reaction-limited or diffusion-limited aggregation kinetics were sensitive to the pH quench depth, relative to the acid-equilibrium constant (pKa) of the surface carboxylic acid groups on the nanoparticles. Since numerous PAGs are commercially available, this approach could be used to study the aggregation of variety of solvent-dispersed nanoparticle systems.
Citation: Journal of Chemical Physics
Pub Type: Journals
nanoparticle, stability, light scattering, pH, aggregation