In Situ Transmission Electron Microscopy of Plasma-Driven Nanoparticle Synthesis in Solution

Plasma-driven solution electrochemistry (PDSE) offers an additive-free approach to nanomaterial synthesis but has not been widely implemented because of the current lack of control strategies, rooted in the limited mechanistic understanding of nucleation and growth that has been inaccessible to direct observation. We report on the real-time visualization of gold nanoparticle nucleation, growth, and coalescence in a thin ionic liquid film using a newly developed in situ plasma-liquid transmission electron microscopy platform. Monomer attachment is identified as the dominant growth process, and the measured growth rates suggest a nucleation-limited regime. Trajectory analysis reveals enhanced nucleation near the film edge, likely due to an increased monomer concentration caused by plasma-induced solvent evaporation. The reported observations provide critical insights into mechanisms and rate-limiting processes and can provide guidance for PDSE-enabled process development to achieve the rapid synthesis of colloidal nanomaterials with a narrow size distribution.