In this work, we demonstrate the systematic and delicate geometry control of Cu₂O nanocrystals by taking advantage of the selective surface stabilization effect. A variety of Cu₂O architectures, evolved from cubes through truncated cubes, cubooctahedrons, truncated octahedrons and finally to octahedrons, were achieved by simply adjusting the added PVP. Based on the understanding of the intrinsic structural features of the cuprite Cu₂O and PVP, we elucidated the underlying shape evolution mechanism. The as-prepared products demonstrated a crystallography-dependent adsorption ability with methyl orange (MeO) as the pollutant. With the advantage of a low cost, high yield and straightforward procedure without pre-formed crystals as sacrificial templates, this method may provide a good starting point for the study of shape construction and morphology-dependent properties of other nanocrystals.

Grain rotation is a well-known phenomenon during high (homologous) temperature deformation and recrystallization of polycrystalline materials. In recent years, grain rotation has also been proposed as a plasticity mechanism at low temperatures (for example, room temperature for metals), especially for nanocrystalline grains with diameter d less than ~15 nm. Here, in tensile-loaded Pt thin films under a high-resolution transmission electron microscope, we show that the plasticity mechanism transitions from cross-grain dislocation glide in larger grains (d>6 nm) to a mode of coordinated rotation of multiple grains for grains with d<6 nm. The mechanism underlying the grain rotation is dislocation climb at the grain boundary, rather than grain boundary sliding or diffusional creep. Our atomic-scale images demonstrate directly that the evolution of the misorientation angle between neighbouring grains can be quantitatively accounted for by the change of the Frank–Bilby dislocation content in the grain boundary.