Unveiling Atomic-Scale Crystal Growth and Radiolysis Dynamics in Nanoreactors Through Real-Time Liquid-Phase Transmission Electron Microscopy

Understanding crystal growth mechanisms at the atomic scale is central to controlling materials synthesis, catalysis, and self-assembly. Liquid-phase transmission electron microscopy (LPTEM) now enables direct visualization of these dynamic processes, yet its performance is critically limited by the window materials that define the liquid cell environment and morphology. Two-dimensional membranes such as graphene and hexagonal boron nitride have advanced the field by offering atomic thinness and mechanical strength, yet challenges remain in fabrication and stability. Here, we introduce monolayer molybdenum disulfide (MoS₂) as a clean, robust, and dose-rate-tolerant window material that forms flat, and nanometer-thick liquid pockets ideal for atomic-resolution imaging. Using real-time LPTEM imaging, we track the nucleation and growth of metallic (Pt) and ionic (NaCl) crystals under controlled irradiation. By correlating electron-beam-induced radiolysis chemistry, role of the window material, and beam-driven crystal kinetics, we reveal how 2D membranes actively regulate reactions in confined liquids, paving the way toward single-atom catalysis and atom-by-atom materials design.