Research Projects of the Gebauer Group

  • Materials World Network (MWN) for Particle-mediated Control Over Crystallization: From the Pre-nucleation Stage to the Final Crystal
    A Materials World Network (MWN) will be formed to investigate mechanisms of particle-mediated crystallization through which mesocrystals — crystals structured on the mesoscale — are created. In biomineral systems, mes-ocrystal formation is a widespread phenomenon mediated by biomolecules and leading to the hierarchical organization commonly associated with these materials. Our ultimate goal is a mechanistic understanding of this process and a set of principles to guide biomimetic strat-egies to create hierarchically organized materials (e.g. bioceramics, photonic solids, energy harvesting materials). The value added by the international collaboration is that it facilitates this goal by combining expertise in chemistry and growth of mesocrystals with capabilities in high-resolution in situ imaging, measurement of interactions, determination of structure, and modeling and simulation from the atomic to mesoscale. Using the calcium carbonate, iron oxide and calcium-silicate hydrate (C-S-H) systems combined with polymers, the project will pursue three thrusts, structured around the key scientific questions: Thrust 1: The pre-nucleation stage, nucleation of primary nanoparticles and intermediate phases - The nature of pre-nucleation clusters will be determined using ion potential measurements, titration and ultracentrifugation. Their solution interaction dynamics will be probed through liquid cell TEM. Thrust 2: Interactions forces between nanocrystals and organic mediators of mesocrystal formation – The interactions responsible for particle co-orientation and reorientation will be determined through a combination of dynamic force spectroscopy (DFS) and modeling. DFS will provide a direct measure of the free energy of the orientation dependent crystal-crystal and -polymer interactions. Experimental measurements are supported by molecular model-ing, which allows us to determine molecular details of the effective interactions and provides parameters for the phase field calculations in Thrust 3. Thrust 3: Post-nucleation particle ag-gregation and co-orientation – The kinetics of particle aggregation, crystallographic orienta-tions of the aggregating particles as a function of time, and structural evolution of mesocrys-talline aggregates will be investigated by liquid cell TEM and ex situ HRTEM. Emphasis will be placed on distinguishing between oriented attachment and orientation following random aggregation either through whole-particle rotation or atomic-scale ripening. These data will be compared to phase-field models of mesocrystal assembly that utilize the interaction energies determined in Thrust 2.
    Leaders: Prof. Dr. H. Cölfen, Prof. Dr. D. Gebauer, Prof. Dr. H. Emmerich
    Year: 2013
    Sponsors: Deutsche Forschungsgemeinschaft (DFG)
    Lifespan: 2013-2017
  • Advanced Hybrids of Calcium Carbonate and Nanocellulose
    Leaders: Prof. Dr. D. Gebauer
    Team: Prof. Dr. L. Bergström
    Year: 2014
    Sponsors: Baden-Württemberg Stiftung (Stuttgart)
    Lifespan: 2014-2017
  • The onset of anisotropy during calcium carbonate and phosphate mineralization
    Calcium carbonate and phosphate behave very distinctly during the early stages of precipitation, es­pecially regarding the earliest development of morphological anisotropy. In this project, time-resolved in situ analyses of precipitation are designed to elucidate the underlying key factors. The goal is to enable a better understanding of the control of polymorphism and morphology of crystals, so as to pave the way to the rational generation of colloidal building blocks.
    Leaders: Prof. Dr. D. Gebauer and Prof. Dr. K. Hauser
    Year: 2016
    Sponsors: DFG
  • A07: Bifunctional hybrid nanoparticles via calcium carbonate crystallization driven by engineered protein surfaces
    This project aims at the defined generation of structurally and functionally anisotropic nanohybrid particles of calcium carbonate and tailor-made genetically engineered proteins via non-classical pathways of crystallization. Iterative cycles of protein design and thorough investigations of their effect on in vitro calcium carbonate precipitation will identify the essential factors underlying this complex process. Eventually, this will pave the way for the rational generation of particle superstructures via directed self-assembly.
    Leaders: Prof. Dr. D. Gebauer, Prof. Dr. A. Marx
    Year: 2016
    Sponsors: DFG
  • Control of crystallisation in minerals
    This project aims to increase our knowledge of the processes of mineral formation and crystallisation. Minerals play a vital role in our environment, for example as reservoirs for carbon dioxide, while also substantially contributing to the Australian economy. Conversely, undesirable formation of minerals can be detrimental to industries from the oil/gas sector through to desalination. Despite the benefits that would come from controlling such crystal growth, progress has been limited by the lack of a complete understanding of how minerals form at the microscopic level. This project aims to combine computer simulation, using the latest petascale resources, with experimental data to yield knowledge that would allow us to manipulate minerals, such as calcium carbonate, with the same control found in nature.
    Leaders: Prof. Dr. J. D. Gale
    Team: Dr. R. Demichelis, Prof. Dr. D. Gebauer, Prof. Dr. C. Putnis
    Year: 2016
    Sponsors: Australian Research Council
    Lifespan: 2016-2019