title: Nanocrystalline calcitic lens arrays fabricated by self-assembly followed by amorphous-to-crystalline phase transformation.
abstract: Natural calcium carbonate-based nanocomposites often have superior physical properties and provide a comprehensive source for bioinspired synthetic materials. Here we present thermodynamically stable, transparent CaCO3 microlens arrays (MLA) produced by transforming an amorphous CaCO3 phase into nanocrystalline calcite. We analyze the structure and properties of crystallized MLA by X-ray scattering, transmitted and polarized light microscopy, and electron microscopy and find that MLA are crystallized in spherulite-like patterns without changing the shape of the microlens. The key finding is that nanocrystallinity of the calcite formed diminishes structural anisotropy on the wavelength scale and results in greatly reduced birefringent effects. The remnant preferred orientation of the optical axes of calcite crystals in the plane of the microlens arrays leads to some directionality of optical properties, which may be beneficial for technical applications.
authors.affiliation: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces , Potsdam 14424, Germany.
authors.forename: Ingo
authors.initials: I
authors.lastname: Schmidt
authors.forename: Kyubock
authors.initials: K
authors.lastname: Lee
authors.forename: Emil
authors.initials: E
authors.lastname: Zolotoyabko
authors.forename: Peter
authors.initials: P
authors.lastname: Werner
authors.forename: Tae Soup
authors.initials: TS
authors.lastname: Shim
authors.forename: You-Kwan
authors.initials: YK
authors.lastname: Oh
authors.forename: Peter
authors.initials: P
authors.lastname: Fratzl
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wagermaier
mesh_terms: D002119:Calcium Carbonate / Q000737:chemistry*; D007909:Lenses; D008958:Models, Molecular; D008968:Molecular Conformation; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology / Q000295:instrumentation*; D055620:Optical Phenomena; D010316:Particle Size; D044367:Phase Transition
chemical_list: D002119:Calcium Carbonate
keywords: X-ray diffraction; biomineralization; crystal growth; nanocrystallites; optical properties