In Situ Observation of Au Nanostructure Evolution in Liquid Cell TEM

Ying-Chen Chen, Jui-Yuan Chen and Wen-Wei Wu, 2017
micrograph of Au nanoparticle structure evolution in situ
Image courtesy of Journal of Physical Chemistry C

Abstract

Gold nanostructures (NSs) have been widely investigated due to their unique properties. Understanding their growth behaviors during synthesis will be beneficial in designing and applying to many functional nanodevices. It is important to enrich the fundamental science and technology of the synthesis and characterization through real time evolution. In this work, we observed the dynamic growth of Au NSs by using liquid in situ transmission electron microscopy (TEM). The solution was sealed in a liquid cell, and the results indicated that the thicker solution layer tended to form multi-twinned decahedral NSs; in contrast, nanoplates easily formed in the thinner solution layer. The silver halide model, relying on side-face structures, and the Wulff construction can be used to explain the formation of NSs. Additionally, we analyzed the growth rate of different morphologies to elucidate their growth behaviors. The growth mechanism and formation kinetics of different shapes of Au NSs were systematically studied, which provided direct evidence toward and extended the study of reaction kinetics for modifying the morphology of NSs.

Impact Statement

HAuCl4 and citric acid were used as a model system to study the growth mechanisms of multi-twin gold nanoparticles in situ. Local liquid thickness influenced the resulting nanomaterial structures with multi-twinned decahedral nanoparticles appearing as the primary structure in thick liquid regions and nanoplates primarily forming in thin liquid regions.