Formation of magnesium calcite mesocrystals in the inorganic environment only by using Ca2+ and Mg2+ and its biological implications

Abstract

Magnesium calcite (Mg-calcite) mesocrystal is widespread in the biominerals with specific functions. Until now, it remains challenging to obtain Mg-calcite mesocrystals without organic additives and the formation mechanism of Mg-calcite mesocrystals in the ocean is not clear yet. We report here the synthesis of corn-like Mg-calcite mesocrystals from pure amorphous calcium carbonate (ACC) via a facile method only by using Ca2+ and Mg2+. The obtained Mg-calcite is composed of many nanocubes with common crystallographic orientation, which shows very good single crystal feature. In the crystallizing procedure, the ACC nanospheres rapidly agglomerate into Mg-calcite corn-like mesocrystal by oriented attachment (OA) in a certain direction, which belongs to the non-classical nucleation. By this method, the molar ratio of Ca2+ and Mg2+ plays a vital role in the whole crystallization procedure, which may shed a new light on disclosing the mechanism behind for the effect of seawater in the formation of biological Mg-calcite in nature.