Self-Assembly in Hopper-Shaped Crystals

Hopper shape is a special type of crystal morphology. Hopper-shaped crystals possess unique properties and show promise in many different applications. The understanding of how the building blocks (atoms, ions, and molecules) assemble into hopper-shaped crystals and how the environmental factors influence the assembly process is critical to the properties and applications of hopper-shaped crystals. In this review, the important interfacial instability theories that outline the underlying mechanisms for the formation of hopper-shaped crystals are discussed. Next, the relevant experimental developments based on three categories of synthetic approaches are discussed: the growth through the control of the solute concentration, the temperature gradient, and the capping agent. At the end of the review, the applications, opportunities, and potential challenges of the hopper-shaped crystals are discussed.