In-Situ Liquid Phase Electron Microscopy for Studying the Dynamics of Colloidal Nanoparticles at the Nanoscale

Beginning with Robert Brown’s original observation in 1828, various techniques have been developed to study the hydrodynamics and interactions of colloidal particles in solution. These techniques have been inspired or followed by development of theories that are capable of describing these fundamental aspects of micron-scale colloidal particles. Yet, many of the underlying assumptions break down at the nanoscale regime, requiring development of new techniques and theories to understand the fundamentals of interactions and dynamics for the nanoscale regime. Liquid phase transmission electron microscopy (TEM), in particular, has the promise of providing information at the single particle level, while imaging within environmental conditions that resemble those inherent to the as-synthesized particles. Direct visualization of nanoparticles and their dynamics at the nanoscale in a sealed liquid cell allows us to study their interactions and rheological behavior directly and in real time. Here, we show our results on studying the dynamics of nanoparticles in aqueous environment using liquid phase TEM imaging by characterizing the diffusion dynamics of individual nanoparticles in their native solution environment while being exposed to the electron beam on the microscope. This study opens up the path for us to use nanoparticles as nanoscale probes to study rheology directly at a length scale intrinsic to many soft matter systems (i.e., sub-100 nm) that are not easily accessible by other methods.