Visualizing Facets Asymmetry Induced Directional Movement of Cadmium Chloride Nanomotor.

Nanomotors in solution have many potential applications. However, it has been a significant challenge to realize the directional motion of nanomotors. Here, we report cadmium chloride tetrahydrate (CdCl 2 ·4H 2 O) nanomotors with remarkable directional movement under electron beam irradiation. Using in situ liquid phase transmission electron microscopy, we show that the CdCl 2 ·4H 2 O nanoparticle with asymmetric surface facets moves through the liquid with the flat end in the direction of motion. As the nanomotor morphology changes, the speed of movement also changes. Finite element simulation of the electric field and fluid velocity distribution around the nanomotor assists the understanding of ionic self-diffusiophoresis as a driving force for the nanomotor movement; the nanomotor generates its own local ion concentration gradient due to different chemical reactivities on different facets.