Mesocrystal

A mesocrystal is a material structure composed of numerous small crystals of similar size and shape, which are arranged in a regular periodic pattern.

It is a form of oriented aggregation, where the small crystals have parallel crystallographic alignment but are spatially separated.

[2] When the sizes of individual components are at the nanoscale, mesocrystals represent a new class of nanostructured solids made from crystiallographically oriented nanoparticles.

The sole criterion for determining whether a material is mesocrystal is the unique crystallographically hierarchical structure, not its formation mechanism.

Alternatively, a mesocrystal could have its pores filled and then it would be similar to a single-crystal material and have some unusual electronic and optical properties.

[5] The spines of sea urchins are composed of mesocrystals of calcite nano-crystals (92%) in a matrix of non-crystalline calcium carbonate (8%).

High-resolution electron microscopy image of a single gamma phase iron oxide nanoparticle. Each dot in the image suggest the position of an iron (III) ion. Left inset is the corresponding Fast Fourier transform of the image. Scale bar: 10 nm. [ 1 ]
Nanosized iron oxide crystals coated with oleic acid can be dispersed in an organic solvent ( toluene ). Upon its evaporation, they regularly arrange (" self-assemble ", left and right panels) into micron-sized mesocrystals (center) or a multilayer (right). Each dot in the left image suggest the position of a nanoparticle (compare to a traditional "atomic" crystal shown in the image above). Scale bars: 100 nm (left), 25 μm (center), 50 nm (right). [ 1 ]