On the influence of capping agents in DNA-templated silver nanoparticle (AgNP) formation kinetics: A single-molecule approach

DNA molecules have been extensively used for the synthesis of metal nanoparticles due to their advantages in controlling the size, shape, and properties of the nanoparticles. In nanoparticle preparation, capping agents play important roles in stabilizing the particles and regulating their growth. Herein, we investigated the effects of three capping agents on the kinetics of DNA-templated silver nanoparticle (AgNP) formation at the single-molecular level. It was demonstrated that the addition of sodium dodecyl sulfate (SDS) most significantly inhibits the particle growth kinetics, resulting in a direct restoration of DNA length. Under identical experimental conditions, morphology characterizations revealed that the addition of SDS resulted in the formation of the smallest particles, consistent with the strong inhibitory effect of SDS observed in the kinetics measurements. In contrast, polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) exhibited weaker inhibiting effects, resulting in little to no DNA restoration behavior. We propose a phenomenological model to explain the sigmoid kinetics followed by an exponential decline shown in the kinetic curves. We conclude that capping agents regulate the properties of AgNPs primarily by influencing the kinetics of nanoparticle growth. Multiple factors, including the regulating effects of capping agent on the AgNP surface, are believed to influence the kinetics.