Friday, November 8, 2019 - 11:00am

Liquid cell transmission electron microscopy (LC-TEM) has emerged as a powerful tool for direct visualization of nanocrystal nucleation and growth at high spatial resolution. Current limitations of the liquid cell sample holders necessitate utilizing the electron beam as the stimulus for initiating nanocrystal formation and other related processes like molecular crystallization, nanoparticle etching, and self-assembly. Electron beam induced chemistry has proven to be considerably more complex than conventional chemical reagents used in flask-based synthesis of nanomaterials. Without enhanced understanding and control over electron beam chemistry, LC-TEM insights into nanocrystal formation and other process cannot be readily translated to enhance our understanding of corresponding bench scale syntheses. In this seminar, I will discuss my group’s recent work on quantitative understanding and control over electron beam induced changes to solution chemistry and its application to studying heterogeneous nucleation. Using the model system of silver nanocrystal growth, which has uniquely quantifiable reaction kinetics, I will discuss our efforts to identify the impacts of the electron beam on solution chemistry and nucleation and growth kinetics of nanocrystals. The outcome of this study is a calibrated solution chemistry that enables tuning nanocrystal nucleation and growth kinetics separately and accounts for details of the complex radiation chemistry. Using this approach, we investigate heterogeneous nucleation of silver nanocrystals with unprecedented reproducibility and quantitative control over supersaturation ratio. We show that heterogeneous nucleation of silver nanocrystals during LC-TEM is influenced by the surface chemistry of the solid-liquid interfaces in the liquid cell sample chamber. I will conclude the talk by discussing recent results on sensing of electron beam induced changes to solution chemistry during LC-TEM.


Taylor Woehls


University of Maryland


NS2 2201