Synthesis and Optical Properties of Mesoporous beta-Co(OH)2/Brilliant Blue G (G250) Hybrid hierarchical structures
2012-03-08, Cong, Huai-Ping, Ren, Xiao-Chen, Yao, Hong-Bin, Wang, Ping, Cölfen, Helmut, Yu, Shu-Hong
New mesoporous β-Co(OH)2/brilliant blue G (G250) hybrid hierarchical structures constructed by thin mesocrystal nanosheets can be synthesized by a one-step refluxing process under the synergistic effect of CTAB and G250. This approach opens up an avenue to access new novel inorganic/dye hybrid materials with hierarchical structures for pigment and electrocatalytic application.
Mesocrystals of vanadium pentoxide : a comparative evaluation of three different pathways of mesocrystal synthesis from tactosol precursors
2011-01-25, Lausser, Christine, Cölfen, Helmut, Antonietti, Markus
Vanadium pentoxide mesocrystals were synthesized from a mineral liquid crystalline precursor phase, a so-called tactosol. For comparative evaluation of solid formation from that phase, the distance between the vanadium pentoxide particles was lowered by three different modes: (a) by adding a 0.1 M NaCl solution, the electric double layer was compressed and controlled particle aggregation was induced; (b) application of external pressure by ultracentrifugation resulted in particle compression and final crystallization; (c) an acrylic acid/ sulfonic acid copolymer was added to introduce polymer-mediated particle alignment and densification. In all three cases, the preorientation of the particles within the liquid crystal remained, and different mesocrystals were formed. This was demonstrated by comparative analysis of the resulting structures by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and polarization microscopy.
Structure-property relationships of a biological mesocrystal in the adult sea urchin spine
2012-03-06, Seto, Jong, Ma, Yurong, Davis, Sean A., Meldrum, Fiona, Gourrier, Aurelien, Kim, Yi-Yeoun, Schilde, Uwe, Sztucki, Michael, Burghammer, Manfred, Maltsev, Sergey, Jäger, Christian, Cölfen, Helmut
Structuring over many length scales is a design strategy widely used in Nature to create materials with unique functional properties. We here present a comprehensive analysis of an adult sea urchin spine, and in revealing a complex, hierarchical structure, show how Nature fabricates a material which diffracts as a single crystal of calcite and yet fractures as a glassy material. Each spine comprises a highly oriented array of Mg-calcite nanocrystals in which amorphous regions and macromolecules are embedded. It is postulated that this mesocrystalline structure forms via the crystallization of a dense array of amorphous calcium carbonate (ACC) precursor particles. A residual surface layer of ACC and/or macromolecules remains around the nanoparticle units which creates the mesocrystal structure and contributes to the conchoidal fracture behavior. Nature's demonstration of how crystallization of an amorphous precursor phase can create a crystalline material with remarkable properties therefore provides inspiration for a novel approach to the design and synthesis of synthetic composite materials.
Preparation of hierarchical mesocrystalline DL-Lysine·HCl–Poly(acrylic acid) hybrid thin films
2011-08-16, Jiang, Yuan, Gong, Haofei, Volkmer, Dirk, Gower, Laurie, Cölfen, Helmut
A novel reprecipitation route is combined with an evaporation process for the synthesis of self-assembled mesocrystalline thin films with at least five hierarchical levels including pattern assembly, fan-shaped patterns, dendrites, fibers with branches, lamellae, and nanoparticles. The hierarchical thin films presented here show several similarities to biological structures such as fern structures.