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Bioinspired Materials

Synthesis
Nature is replete with hierarchically assembled hybrid materials where the multi‐scale structures confer unique properties and functions. The objective of the Bioinspired Materials FWP is to explore biomimetic pathways for design and synthesis of hierarchically self‐assembled functional materials with controllable properties for energy applications. Our approach mimics Nature using organic templates coupled to mineralization proteins to control the growth of the inorganic phase to form self‐assembled nanocomposites. Magnetotactic bacteria with chains of magnetic nanocrystals serve as inspiration and sources of mineralization proteins.  We are developing new methods to create dynamic tunable nanostructures using reversible linkages for assembly/disassembly of inorganic nanocrystals in response to environmental conditions. This highly interdisciplinary research is facilitated by FWP investigators with diverse backgrounds in several disciplines. The synergistic combination of synthesis, materials characterization and theory provides a powerful approach for understanding mineralization processes in Nature and for expanding on these processes to grow novel nanocrystals in organic matrices in vitro. This controlled bottom‐up approach for materials design aligns well with DOE’s proposed directions in “control science”, allowing for the synthesis of nanostructures such as complex magnetic nanocrystals with potential energy relevance.

This research is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering.

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  • Salt-induced 2D hexagonal superlattices of polyethylene-glycol functionalize gold nanoparticles at the vapor-liquid interface.

    Researchers have developed a method to self-assemble close to perfect structures of gold nanoparticles.  The gold nanoparticles were grafted with polymer chains into 2D supercrystals by controlling salt concentration.  The materials were characterized using high-resolution synchrotron surface X-ray scattering methods, including grazing incidence small angle X-ray scattering and X-ray reflectivity, at the Advanced Photon Source, a U.S. Department of Energy, Office of Science User Facility.

  • Swapping out hard-shelled nanoparticle models for the soft-shelled variety has led to theoretical results in tune with experimental findings for building supercrystal nano materials. These are fundamental new type of material that are built from nanoparticles displaying long range order. In the process of building, the nanoparticles interact, jockeying for position in the lattice. Whereas models of hard-shelled nanoparticles only clink against each other, the flexible exterior of soft-shelled nanoparticles makes their interactions much more complex.

  • Researchers have developed the first theoretical model of the self-assembly of nanocubes that have been coated with polymers, including DNA and have shown exciting possibilities for experimentally programming self-assembled structures.  While spherical nanoparticles can align in any direction, nanocubes will only align with their faces oriented in certain ways.

  • Using the surface sensitive synchrotron X-ray capabilities at the U.S. Department of Energy’s Advanced Photo Source, researchers were able to figure out that the structure of the vapor/liquid interface of an ionic liquid is actually made up of tiny crystals even 100 °F above the liquid’s melting point.Ionic liquids consist of positive and negative ions.

  • A new group of bacteria has been discovered in Death Valley’s Badwater Basin that makes nanoparticles of both magnetite (Fe3O4) and greigite (Fe3S4). Magnetotactic bacteria use these tiny magnets as part of their navigation system to align themselves along the Earth’s magnetic field. Typical magnetotactic bacteria do not make both magnetite and greigite and the discovery dispels the notion that greigite-producing bacteria live only in marine environments.

  • Using computer simulations, researchers are able to watch how a random mixture of gold nanoparticles with two different DNA strands as linkers assemble right on their computer screen. The magic starts with just a fraction of the nanoparticles forming a large cluster like a plate of spaghetti and meatballs. Within this random cluster, small ordered regions form and eventually lock together into a large uniform array of particles held together with DNA strands. Using computer simulations they also predict previously unseen structures.

  • Ions in water with the same charge, e.g. Fe3+ and La3+, behave dramatically differently at the air/water interface when interacting with a charged surface. This difference violates classic electrostatic theory. The distributions of specific ion types were determined with unprecedented precision using newly developed surface sensitive synchrotron x-ray scattering and spectroscopic techniques. The research team was able to use these results to verify their recently-developed theoretical model that takes into account both classical and effective quantum behavior.

  • Understanding the mechanism of action of mineralization proteins, such as Mms6 that promote the growth of uniform nanocrystals of magnetite as well as cobalt ferrite under room temperature conditions, enables us to design more stable synthetic analogs that can perform these functions in a much more robust manner. To elucidate the mechanism of Mms6, X-ray fluorescence spectroscopy techniques were developed at the Ames Laboratory and showed that Mms6 binds selectively to Fe3+ and in large quantities, compared to other ions.

  • The ability to mimic the hierarchical order at multiple length scales in natural materials, such as bone, is crucial for a bottom-up approach to materials design. Being able to mimic the formation of self-assembled nanocomposites of calcium phosphate using block copolypeptides as templates has allowed us to grow hydroxyapatite nanocrystals in the organic matrix with sizes and morphologies similar to that seen in natural bone. The hydroxyapatite nanocrystal size in the synthetic nanocomposites was determined controlled through the use of citrate, similar to native bone.

Publications


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