Kinetics of reaction of gold nanoparticles following partial removal of stabilizers

Abstract

Citrate-stabilized gold nanoparticles (Au NPs) of 17-nm diameter were allowed to react following partial depletion of the stabilizer using dialysis. Kinetics of the reaction was investigated by following time-dependent changes in the visible extinction spectrum. Thus, surface plasmon resonance peak (SPR) of isolated Au NPs (reactant) at 522 nm decreased, while SPR peak due to product—which was agglomerated Au NPs-occurring at 600 nm increased with time. The reaction followed first-order kinetics with respect to concentration of reactant (Au NP) with a rate constant on the order of (2.10 ± 0.34) × 10⁻³ min⁻¹. Further, product concentration correspondingly increased with time. Transmission electron microscopy investigation indicated the presence of individual NPs, along with agglomerated structures in the beginning of reaction-the extent of which increased with time, rather than the formation of smaller agglomerates. A model has been proposed based on reaction of individual NPs with agglomerated structures which accounted for the observed kinetics.