Understanding details of atomic structures and changes of nanoparticles during growth and structure changes is important since they determine physical and chemical properties of nanoparticles. However, due to their small size and heterogeneity, static and dynamic structure information of nanoparticles in their native solution phase cannot be easily accessible by conventional analytical methods. The recent advent of the in-situ liquid cell for transmission electron microscopy is just such a tool. We use in situ liquid phase TEM and statistical image analysis to identify growth trajectories of individual nanoparticles along with ensemble behaviors. We develop time-resolved 3D reconstruction to track 3D atomic structure changes of individual nanoparticles in solution chemistry. We first observe the diffraction patterns from individual Pt nanoparticles as they rotate in the liquid cell, and ultimately, we are able to align and invert those images to obtain the 3D atomic structure of individual particles freely moving in liquid. Positions of entire atoms composing an individual nanoparticle are identified onto 3D density maps. Such atomic positions unveil different degree of crystallinity in the core, grain boundary, and surface of a single nanoparticle. We expand this method to time domain to perform time-resolved 3D structure reconstruction of a nanoparticle while the particle undergoes structural changes in solution. The time-resolved 3D density map shows details of spatial fluctuation of individual atoms during structural transition of a single nanoparticle.<br/>

Nanoparticle chemistry in solution observed by time-resolved 3D TEM

255th National Meeting (2018)

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