EAGER: Developing an Imaging Tool to Investigate the Dynamics of Nanoparticles in 2D

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Non-Technical AbstractSolutions, dispersions and gels play an important role in life and the physical sciences. These systems are important in areas ranging from the traditional, such as agriculture and cosmetics, to the cutting edge, such as new materials and nanomotors. This project will develop a new imaging technology that will allow us to visualize the motion of nanometer scale particles with high resolution for long periods of time. These studies will open a large number of opportunities in the imaging of nanoscopic materials across a range of materials areas. These include the crystallization of polymers in ultrathin films, polymer nanoparticle-composites, the diffusion of nanoparticles in gels, in situ monitoring of separations of nanoparticles and polymers, in operando monitoring of electrochemical cells for battery applications, 2D phase separation behavior, glassy and jammed nanoparticle assemblies, the dynamics of nonequilibrium systems, and in the monitoring of nanomotors, where propulsion is provided by chemical reactions. These studies will open pathways to addressing some of the most longstanding problems in materials and provide insight into controlling non-equilibrium packing of materials, including the dynamics and ageing of glassy materials, to structure/property relationships of glassy materials, and, ultimately, to the parameters that lead to rare events, like the unjamming of particles which can impact materials science but, also, area as far-reaching as geoscience, where such unjamming phenomena, as in the unjamming of tectonic plates, lead to earthquakes. Technical AbstractThis project will develop a visualization protocol, along with the design of analysis routines and a revolutionary SEM sample cell to explore the dynamics of 2D assemblies of nanospheres (NSs) and nanorods (NRs) as the areal density of the nanoparticles (NPs) increases, bringing the NPs from a low density liquid state into a jammed or glassy state; along the way, structures and structure dynamics will be monitored at unprecedented spatial resolution. Imaging with electron microscopy provides the most valuable direct information on nanoscale structure. However, studies of typical solvated particles are limited by the high vapor pressure of the solvents which limits both spatial resolutions and the temporal duration of the studies. We will utilize ionic liquids (ILs) as an alternate platform to monitor solvated soft material dynamics by electron microscopy eliminating the need for a liquid cell. The proposed studies will advance our knowledge by developing instrumentation, versatile sample cell, and imaging software, to tackle a long-outstanding, truly grand challenge in materials science and physics, i.e., the nature of glassy and jammed systems. Through the development of the instrumentation and experimental protocols, we will gain insight into the dynamics of jammed and glassy materials, quantify the real-space structural rearrangements arising from NP interactions, and elucidate the heterogeneous nature of dynamics in glassy materials, a topic of intense theoretical interest.