Abstract
The selective shortening of gold nanorods (NRs) is a directional etching process that has been intensively studied by UV-Vis spectroscopy because of its direct impact on the optical response of these plasmonic nanostructures. Here, liquid-cell transmission electron microscopy is exploited to visualize this peculiar corrosion process at the nanoscale and study the impacts of reaction kinetics on the etching mechanisms. In situ imaging reveals that anisotropic etching requires a chemical environment with a low etching power to make the tips of NRs the only reaction site for the oxidation process. Then, aberration-corrected TEM and atomistic simulations were combined to demonstrate that the disparity between the reactivity of the body and the ends of NRs does not derive from their crystal structure but results from an inhomogeneous surface functionalization. In a general manner, this work highlights the necessity to consider the organic/inorganic natures of nanostructures to understand their chemical reactivity.
Highlights
IntroductionFrom theoretical point of view, different approaches have been actively developed to understand the role of surfactants on the structure of metal nanoparticles.[26,27] Generally, methods of quantum chemical calculations enable a detailed study of a system at the atomic level, but the computational cost for such methods is high
Oxidative etching plays a key role in the dynamics of metallic nanostructures in their formation or application media
They concluded that the strong oxidizing power of OH and H2O2 drives this corrosion processes but the presence of chlorine ions (Cl−) is necessary to lower the redox potential of the reaction and stabilize tetrachloro gold complexes ([AuCl4]−)
Summary
From theoretical point of view, different approaches have been actively developed to understand the role of surfactants on the structure of metal nanoparticles.[26,27] Generally, methods of quantum chemical calculations enable a detailed study of a system at the atomic level, but the computational cost for such methods is high. To overcome these difficulties, classical molecular dynamic (MD) approaches involving force fields with different level of accuracy were developed to investigate the evolution of large molecular assemblies for long periods. We combine experimental and theoretical investigations to demonstrate at the atomic scale the key roles of degradation kinetics and capping agents in the selective shortening of gold nanorods (NRs) in oxidative media
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