18. Liquid Phase TEM Investigations of Crystal Nucleation, Growth, and Transformation

The scarcity of high-resolution, in situ tools has left many fundamental questions regarding crystallization processes unanswered. Recent years have seen many advances in transmission electron microscopy (TEM) approaches that allow TEM observations of liquid environments. These liquid phase TEM techniques provide an in situ platform for investigating the early events in materials formation and understanding the mechanisms by which crystals develop. In this chapter, we provide an overview of the liquid phase TEM experimental platforms and discuss recent studies that use the technique to address open questions in crystallization. We first highlight liquid phase TEM investigations into the calcium carbonate system, where the technique provides insights into the formation pathways that take the mineral from its solvated state to one of various solid phases and the effect that an organic additive can have on such processes. In the following section, we discuss studies of metal nanoparticle formation that investigate the mechanisms of nucleation and growth from a precursor solution, as well as the development into faceted nanocrystals in the presence of an organic ligand. We close the chapter with a discussion of areas for future development that would broaden the utility of liquid phase TEM.