Synthesis of CaF_2 Single Crystal Induced by Langmuir Monolayers

Crystallization of inorganic solids at self-organized organic or biomacromolecular surfaces is an important process in biomineralization and crystal engineering. Thereinto, Langmuir monolayers are often used as simple models of biomineralization; they can guide the growth of oriented crystals of specific structure, size, and morphology. In this paper, the growth of the CaF2 crystals induced in situ by Langmuir monolayers as the template was investigated by means of SEM, XPS and XRD. The results of XRD show that CaF2 grows only along the (111) face under benhenic acid (BA) monolayer, which indicates (111) direction is preferable orientation for the growth of CaF2 crystals; SEM shows that the morphology of the CaF2 crystals induced by BA monolayer is relatively regular and simplex, but in the bulk solution, it's irregular and easy to form large size grains. Those may be reasonably explained by lattice matching between the benhenic acid headgroups in the monolayer and the CaF2 crystals lattice which were fabricated under monolayer.