High-resolution STEM observation of the dynamics of Pt nanoparticles in a liquid

The dynamics of Pt nanoparticles (NPs) in water are observed by high-resolution scanning transmission electron microscopy with a home-made static sandwich-type liquid cell (LC). Carbon is coated on both sides of the membrane windows of the LC to make them conductive. The slow motion of Pt NPs in thin water droplets enables us to acquire high-resolution scanning transmission electron microscopy images. Using a dose rate of 3 x 10(5) e nm(-2)s, some Pt NPs with a diameter of less than 2 nm disappear into the water, some move around, and others repeatedly attach to and detach from each other. The density of Pt NPs larger than 2 nm remains unchanged with further observation. However, by increasing the dose rate to 5.3 x 10(5) e nm(-2)s, the Pt NPs gather at the beam illumination area, and then form aggregates with chain network structures. It is also determined that the NPs attach to each other at their {111} surfaces.