Quantifying Chemical and Electrochemical Reactions in Liquids by in situ Electron Microscopy

Nanomaterial synthesis and electrochemical process usually involve liquid environments. Studying and understanding such processes in their native environment on the nanoscale is essential to improve the properties of advanced functional materials and nanodevices. In situ Liquid Cell Transmission Electron Microscopy (LCTEM), under rapid development, is a fascinating and versatile characterizing platform that has two advantages: (1) allows high spatial and temporal resolution; and (2) allows to observe dynamic processes in liquid directly.
This PhD thesis focuses in identifying the critical aspects and developing a robust imaging analysis method for quantitatively understand chemical and electrochemical process during in situ liquid electron microscopy. By using two custom-made liquid cells (an electrochemical scanning electron microscopy (EC-SEM) platform and Liquid Flow S/TEM holder) beam-induced and bias-induced nanocrystal growth was investigated. Also, the effect of surfactant on the formation of gold (Au) nanoparticles (NPs) by in situ liquid STEM was explored and quantified. Particularly, the crystal growth processes for Au NPs was observed directly. Moreover, systematic in situ study of electrochemical deposition of copper (Cu) by electrochemical liquid scanning electron microscopy (EC-SEM) was done in order to direct observe the formation of dendritic structures. Finally the shape evolution from solid to hollow structures through galvanic replacement reactions were observed for different silver (Ag) nanotemplates (cube, rod, nanowires) and gold chloride solution.
Results demonstrated that by combining in situ LTEM and ECSEM microscopy with quantitative analysis and systematic studies, meaningful information about the controllable synthesis of metal NPs is achievable.