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Self-Organization of Complex Polycrystalline Silica-Carbonate Biomorphs

Title: Self-Organization of Complex Polycrystalline Silica-Carbonate Biomorphs.
Name(s): Nakouzi, Elias, author
Steinbock, Oliver, professor directing dissertation
Bertram, R. (Richard), university representative
Knappenberger, Kenneth L., committee member
Mattoussi, Hedi, committee member
Florida State University, degree granting institution
College of Arts and Sciences, degree granting college
Department of Chemistry and Biochemistry, degree granting department
Type of Resource: text
Genre: Text
Issuance: monographic
Date Issued: 2016
Publisher: Florida State University
Place of Publication: Tallahassee, Florida
Physical Form: computer
online resource
Extent: 1 online resource (147 pages)
Language(s): English
Abstract/Description: A key challenge for modern chemistry is the production of mesoscopic complexity and hierarchical order to ultimately bridge the gap between the molecular world and functional microdevices. As proof of concept, nature shows unambiguously that this approach can be rewarding. In particular, natural biominerals such as nacre, bone, and tooth enamel, consist of ordinary nanoscale components, yet assemble complex polycrystalline materials that are clearly superior to their synthetic counterparts. In this context, an exciting model system for biomimetic crystallization is the assembly of biomorphs by the co-precipitation of silica and metal carbonates. Despite being formed by purely inorganic processes, these structures show "life-like" morphologies such as twisted helices and cardioid leaves. At the nanoscale, silica-carbonate biomorphs consist of crystalline nanorods that assemble hierarchical architectures reminiscent of natural biominerals. In this research work, we improve the level of control over the growth process and quantitatively characterize the biomorph structures beyond simple qualitative observations. We report the synthesis of silica-carbonate biomorphs in single-phase, gradient-free solutions that differ markedly from the typical solution-gas or gel-solution setups. Our experimental approach reveals novel biomorph structural motifs, reduces transients in the chemical conditions, and expands the upper pH limit for biomorph formation to over 12 where silica is essentially soluble. Moreover, the single-phase approach significantly increases the duration of growth to assemble biomorph networks that extend to several millimeters. These unusually long biomorphs allow the first quantitative measurements of mesoscopic parameters such as the helix wavelength, period, width, and linear as well as tangential growth velocities. We find that the latter quantities are system-specific and tightly conserved during many hours of growth. We also systematically characterize the biomorph sheets and report the existence of an additional level of self-organization that creates oscillatory height variations along the sheet surface. These topographic features take the form of either concentric rings or disordered, patchy patterns with a wavelength of approximately 6.5 μm that shows no pronounced dependence on the reactant concentrations. These undulations are accompanied by a systematic out-of-plane displacement of the nanorods. Our results are discussed in the context of an earlier hypothesis that predicts pH oscillations near the crystallization front. We further investigate the effect of inorganic dopants that influence the morphological, compositional, and crystallographic properties of biomorphs. In the case of Pb²⁺ and Ag⁺ ions, biomorph growth is disrupted by the formation of competing precipitates. Similarly, the addition of Ca²⁺, Mg²⁺, and Zn²⁺ induces the rapid crystallization of witherite or amorphous silica-carbonate aggregates at enhanced growth rates. By comparison, the addition of strontium ions results in the assembly of classic biomorphs such as cardioid sheets and helices. Another aspect of the project lies at the overlap between geochemistry, paleontology, and astrobiology. To date, these fascinating biomorph microstructures have only been synthesized using model laboratory solutions. We report that mineral self-assembly can be also obtained from natural alkaline silica-rich water deriving from serpentinization. Specifically, we obtain water samples from the Ney springs in California and demonstrate the self-assembly of nanocrystalline biomorphs of barium carbonate and silica, as well as the formation mesocrystals and crystal aggregates of calcium carbonate with complex biomimetic textures. Our results suggest that silica-induced mineral self-assembly could have been a common phenomenon in alkaline environments of the early Earth and Earth-like planets. Moreover, the structural complexity obtained from these simple crystallization reactions in the natural Ney water further blurs the boundaries between geochemical and biological microscale morphologies that not too long ago were perceived as sharp and well-defined.
Identifier: FSU_FA2016_Nakouzi_fsu_0071E_13624 (IID)
Submitted Note: A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the Doctor of Philosophy.
Degree Awarded: Fall Semester 2016.
Date of Defense: November 17, 2016.
Keywords: Biomimetics, Biomorph, Crystallization, Hierarchical, Self-organization, Silica
Bibliography Note: Includes bibliographical references.
Advisory Committee: Oliver Steinbock, Professor Directing Dissertation; Richard Bertram, University Representative; Ken L. Knappenberger, Committee Member; Hedi Mattoussi, Committee Member.
Subject(s): Chemistry, Physical and theoretical
Persistent Link to This Record:
Host Institution: FSU

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Nakouzi, E. (2016). Self-Organization of Complex Polycrystalline Silica-Carbonate Biomorphs. Retrieved from