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. 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. Helmut Cölfen discovered and named mesocrystals in 2005 during his studies on biominerals. He suggested that their growth was due to a non-classical, self-assembly based process. Mesocrystal is an abbreviation for mesoscopically structured crystal, where individual subunits often form a perfect 3D order, as in a traditional crystal where the subunits are individual atoms. This is when a mesocrystal is formed by filling organic matrix compartments with crystalline matter. This crystalline matter would be oriented by the organic matrix. This is the process of biomineralization and this is how mesocrystals are produced in nature. In most cases mesocrystals form nanoparticles in solution. These nanoparticles aggregate and arrange in crystallographic formation, without any additives. The main causes of this ordering are tensorial polarization forces and dipole fields. Formation with mineral bridges occur with the formation of nanocrystals. Growth is quenched at this stage by the absorption of a polymer into the nanoparticle surface. Now mineral bridges can nucleate at the defect site, within the growing inhibition layer on the nanocrystal. Through this, a new nanocrystal grows on the mineral bridge, and the growth is again stopped by the polymer. This process is repeated until the crystal builds up. This argument for formation of mesocrystals requires only a confined space that the reaction takes place in. As the nanoparticle grow into crystals, they have no choice but to align with each other in such a confined space.