Formation mechanisms of two-dimensional nanostructures in wet syntheses are poorly understood. Even more enigmatic is the influence of hydrodynamic forces. Here we use liquid flow cell transmission electron microscopy to show that layered double hydroxide, as a model material, may form via the oriented attachment of hexagonal nanoparticles; under hydrodynamic shear, oriented attachment is accelerated. To hydrodynamically manipulate the kinetics of particle growth and oriented attachment, we develop a microreactor with high and tunable shear rates, enabling control over particle size, crystallinity and aspect ratio. This work offers new insights in the formation of two-dimensional materials, provides a scalable yet precise synthesis method, and proposes new avenues for the rational engineering and scalable production of highly anisotropic nanostructures.
LC-TEM was used to study the contribution of hydrodynamic forces in the synthetic mechanisms of 2D layered double hydroxide nanomaterials. Controlling the flow rate within the liquid allowed the authors to modulate the hydrodynamic shear forces acting on the nanoparticles. They observed flow accelerated the oriented attachment of the nanoparticles.