Nanoscale materials transformations revealed by liquid phase TEM

Nanoscale materials often undergo structural, morphological, or chemical changes, especially in solution processes, where heterogeneity and defects may significantly impact the transformation pathways. Liquid phase transmission electron microscopy (TEM), allowing us to track dynamic transformations of individual nanoparticles, has become a powerful platform to reveal nanoscale materials transformation pathways and address challenging issues that are hard to approach by other methods. With the development of modern liquid cells, implementing advanced imaging and image analysis methods, and strategically exploring diverse systems, significant advances have been made in liquid phase TEM, including improved high-resolution imaging through liquids at the atomic level and remarkable capabilities in handling complex systems and reactions. In the past more than a decade, we spent much effort in developing and applying liquid phase TEM to elucidate how atomic level heterogeneity and defects impact various physicochemical processes in liquids, such as growth, self-assembly of nanoparticles, etching/corrosion, electrodeposition of alkali metals, catalyst restructuring during reactions, and so on. This article provides a brief review of the liquid phase TEM study of nanoscale materials transformations, focusing on the growth of nanomaterials with distinct shape/hierarchical structures, such as one-dimensional (1D) growth by nanoparticle attachment, two-dimensional (2D) growth with nanoparticles as intermediates, core-shell structure ripening, solid-liquid interfaces including those in batteries and electrocatalysis, highlighting the impacts of heterogeneity and defects on broad nanoscale transformation pathways.