Unravelling Kinetic and Thermodynamic Effects on the Growth of Gold Nanoplates by Liquid Transmission Electron Microscopy

Abstract

The growth of colloidal nanoparticles is simultaneously driven by kinetic and thermodynamic effects that are difficult to distinguish. We have exploited in situ scanning transmission electron microscopy in liquid to study the growth of Au nanoplates by radiolysis and unravel the mechanisms influencing their formation and shape. The electron dose provides a straightforward control of the growth rate that allows quantifying the kinetic effects on the planar nanoparticles formation. Indeed, we demonstrate that the surface-reaction rate per unit area has the same dose-rate dependent behavior than the concentration of reducing agents in the liquid cell. Interestingly, we also determine a critical supply rate of gold monomers for nanoparticle faceting, corresponding to three layers per second, above which the formation of nanoplates is not possible because the growth is then dominated by kinetic effects. At lower electron dose, the growth is driven by thermodynamic and the formation and shape of nanoplates are directly related to the twin-planes formed during the growth.

Light-Induced Polarization-Directed Growth of Optically Printed Gold Nanoparticles

“…31 recently described the reduction of aqueous platinum ions onto Au NPs observing a preferential deposition in the NPs hot spots, in agreement with our findings. From the FE-SEM images, it is evident that the Au NPs do not grow following any crystallographic order, which is consistent with the fast growing rates 34 and the absence of surface molecules with preferential selectivity to crystallographic planes (such as PVP). The anisotropic growth must have a different origin.…”

Two-Dimensional Colloidal Nanocrystals

“…Defect induced anisotropy, such as twin plane in fcc metals, has been widely studied and is one of the major driving force for two-dimensional growth, and can yield metal nanoprisms or nanoplates ( Figure 4). [53][54][55][56] This growth mechanism will be developed in part 2. Because some nanoparticles have shapes that do not correspond to their thermodynamic equilibrium shapes, kinetic effects have to be taken into account.…”

Polyvinylpyrrolidone-induced anisotropic growth of gold nanoprisms in plasmon-driven synthesis

“…Gold (Au) nanostructures are anticipated to provide an ideal system for exploring the plasmon-mediated growth process; they exhibit similar crystallographic structures and plasmonic properties to Ag nanostructures, but boast superior resistance to both chemical oxidation and electron-beam damage [13][14][15][16] . A mechanistic investigation of these photochemical reactions in Au nanomaterials is therefore expected to lend fundamental insights into this process and inform a general description of plasmon-mediated nanocrystal growth.…”