An Alkanethiol-Surfactant Bilayer To Prevent Shape Conversion of Anisotropic Silver Nanoparticles and Probe Their Formation Mechanisms

Anisotropic nanoparticles can be synthesized under kineticcontrolbut may undergo subsequent shape changes due to atomic reorganization.Furthermore, their synthesis involves rapid steps, which are challengingto monitor in situ. Here, we show how a nanoemulsion of alkanethiolswith an ethoxylated surfactant, easily prepared and metastable formonths, can simultaneously prevent shape reorganization and arrestreaction kinetics. We illustrate this generic method on the silvernanoplates synthesized in concentrated acetic acid aqueous solutions,in which rapid shape reorganization occurs. We show that there existsan optimum thiol concentration corresponding to full coverage of allsilver surface atoms, which can be simply calculated from particledimensions. Furthermore, we demonstrate that arresting nanoparticleformation can be achieved within milliseconds using a tandem rapidmixers scheme in a continuous flow setup, allowing ex situ monitoringof the reaction.

Automated summary

In this study, a nanoemulsion of alkanethiols with an ethoxylated surfactant was used to prevent shape reorganization and arrest reaction kinetics of anisotropic nanoparticles. The optimum thiol concentration for full coverage of silver surface atoms in the synthesis of silver nanoplates was determined based on particle dimensions. The formation of nanoparticles was effectively stopped within milliseconds using a tandem rapid mixers scheme in a continuous flow setup, allowing ex situ monitoring of the reaction.