Emergent Nanostructures: Water‐Induced Mesoscale Transformation of Surfactant‐Stabilized Amorphous Calcium Carbonate Nanoparticles in Reverse Microemulsions

Li, M.; Mann, Stephen

doi:10.1002/adfm.200290006

Cited by 160 publications

(113 citation statements)

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“…Similar observations have been reported when different amounts of water-in-isooctane NaAOT microemulsions of constant droplet size (w = 10) are added to isooctane dispersions of alkylbenzenesulfonate-coated amorphous calcium carbonate (ACC) nanoparticles. [85] Hydration of the ACC nanoparticles results in aggregation followed by , n = 34) gives monodisperse spheroidal aggregates of densely packed 5-nm-diameter surfactant-coated vaterite nanoparticles, whereas weak interactions at n = 3400 produce discrete vaterite nanoparticles, 130 nm in size. Significantly, intermediate levels of coupling produce anisotropic nanostructures, such as spindle-shaped aggregates of 18-nm-sized vaterite nanoparticles (n = 170) and high aspect-ratio bundles of aligned 10-nm-wide twisted vaterite nanofilaments (n = 340), both of which are assembled by surfactant interdigitation between adjacent particles.…”

Section: Mesoscale Transformations and Emergent Nanostructuresmentioning

confidence: 99%

“…[85] These structures were synthesized in water-in-oil microemulsions, but significantly, similar complex architectures can be prepared in aqueous supersaturation solutions. For example, barium sulfate and chromate nanofilament bundles and cones were obtained in aqueous solutions of anionic polyelectrolytes [86,87] or hydrophilic block copolymers with a polyanionic domain.…”

Section: Mesoscale Transformations and Emergent Nanostructuresmentioning

confidence: 99%

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Higher‐Order Organization by Mesoscale Self‐Assembly and Transformation of Hybrid Nanostructures

2003

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The organization of nanostructures across extended length scales is a key challenge in the design of integrated materials with advanced functions. Current approaches tend to be based on physical methods, such as patterning, rather than the spontaneous chemical assembly and transformation of building blocks across multiple length scales. It should be possible to develop a chemistry of organized matter based on emergent processes in which time- and scale-dependent coupling of interactive components generate higher-order architectures with embedded structure. Herein we highlight how the interplay between aggregation and crystallization can give rise to mesoscale self-assembly and cooperative transformation and reorganization of hybrid inorganic-organic building blocks to produce single-crystal mosaics, nanoparticle arrays, and emergent nanostructures with complex form and hierarchy. We propose that similar mesoscale processes are also relevant to models of matrix-mediated nucleation in biomineralization.

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Section: Mesoscale Transformations and Emergent Nanostructuresmentioning

confidence: 99%

Section: Mesoscale Transformations and Emergent Nanostructuresmentioning

confidence: 99%

Higher‐Order Organization by Mesoscale Self‐Assembly and Transformation of Hybrid Nanostructures

2003

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“…Thus, in cases in which hydration is strong, such as in apatite, the final product remains hydrated, whereas in cases of weak hydration, such as calcite, the final product is virtually anhydrous. Hydrated amorphous carbonate precursors, which are not usually encountered in materials processing, are reported in biomineralization (32)(33)(34). Similarly, apatite formation in new bone goes through a series of nanophase precursors (17).…”

Section: Hydrated Surfaces Gels and Hydrous Phasesmentioning

confidence: 99%

Energetic clues to pathways to biomineralization: Precursors, clusters, and nanoparticles

Navrotsky¹

2004

Proc. Natl. Acad. Sci. U.S.A.

492

410

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Nanoparticle and nanocluster precursors may play a major role in biomineralization. The small differences in enthalpy and free energy among metastable nanoscale phases offer controlled thermodynamic and mechanistic pathways. Clusters and nanoparticles offer concentration and controlled transport of reactants. Control of polymorphism, surface energy, and surface charge on nanoparticles can lead to morphological control and appropriate growth rates of biominerals. Rather than conventional nucleation and growth, assembly of nanoparticles may provide alternative mechanisms for crystal growth. The Ostwald step rule, based on a thermodynamic view of nucleation and growth, is supported by the observation that more metastable phases tend to have lower surface energies. Examples from nonbiological systems, stressing the interplay of thermodynamic and kinetic factors, illustrate features potentially important to biomineralization. Biomineralization, the production of inorganic phases (oxides, sulfides, silica, carbonates, and phosphates) by living organisms, produces metabolic energy and͞or mechanical support for a variety of organisms from unicellular to mammalian. Although the starting point for the concentration and transformation of components in an aqueous medium to form crystals is generally assumed to be an aqueous solution containing dissolved ions, there is increasing evidence that clusters, nanoscale amorphous precipitates, and other more complex precursors in the aqueous phase may play an important role in crystallization (1-3). The purpose of this article is to summarize some of the features known about these complex nanoscopic pathways to crystallization in nonliving systems, discuss implications for biomineralization, suggest possible ways in which organisms can control the phases formed and their morphology using nanoscale intermediates, and propose specific features to look for in biomineralizing systems as evidence for such pathways. Emphasis is on biologically controlled rather than biologically induced mineralization, because the former involves much more delicate control of polymorphism, crystal morphology, and composite shape. It is argued that such control can be achieved by mechanisms involving nanoparticle precursors and their complex interactions with biomolecules. Because crystallization involves both thermodynamic and kinetic controls, both energetics and mechanisms are discussed, with emphasis on their interplay. Energetics and the Control of PolymorphismMany of the compositions that form as biominerals can exist in several different structural modifications: calcite, aragonite, and vaterite for CaCO 3 ; wurtzite and sphalerite for ZnS; numerous iron and manganese oxides and oxyhydroxides; quartz, cristobalite, tridymite, and many open zeolitic structures for SiO 2 as well as in poorly crystalline, amorphous, and hydrated forms. Although one crystalline polymorph is thermodynamically the most stable under a given set of conditions (temperature, pressure, oxygen, and water fugacity), others are ...

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“…Abiotically, ACC is easily formed by mixing aqueous solutions at or below room temperature. These solutions can be totally inorganic or they can contain small organic species which affect the formation and persistence of ACC (13)(14)(15)(16)(17)(18)(19)(20). Increasing interest in CO 2 sequestration has led to proposals and pilot projects in which large plumes of supercritical carbon dioxide would be introduced into deep saline aquifers (21)(22)(23)(24)(25).…”

mentioning

confidence: 99%

Transformation and crystallization energetics of synthetic and biogenic amorphous calcium carbonate

Radha

Forbes

Killian

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

422

449

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Amorphous calcium carbonate (ACC) is a metastable phase often observed during low temperature inorganic synthesis and biomineralization. ACC transforms with aging or heating into a less hydrated form, and with time crystallizes to calcite or aragonite. The energetics of transformation and crystallization of synthetic and biogenic (extracted from California purple sea urchin larval spicules, Strongylocentrotus purpuratus) ACC were studied using isothermal acid solution calorimetry and differential scanning calorimetry. Transformation and crystallization of ACC can follow an energetically downhill sequence: more metastable hydrated ACC → less metastable hydrated ACC ⇒ anhydrous ACC ∼ biogenic anhydrous ACC ⇒ vaterite → aragonite → calcite. In a given reaction sequence, not all these phases need to occur. The transformations involve a series of ordering, dehydration, and crystallization processes, each lowering the enthalpy (and free energy) of the system, with crystallization of the dehydrated amorphous material lowering the enthalpy the most. ACC is much more metastable with respect to calcite than the crystalline polymorphs vaterite or aragonite. The anhydrous ACC is less metastable than the hydrated, implying that the structural reorganization during dehydration is exothermic and irreversible. Dehydrated synthetic and anhydrous biogenic ACC are similar in enthalpy. The transformation sequence observed in biomineralization could be mainly energetically driven; the first phase deposited is hydrated ACC, which then converts to anhydrous ACC, and finally crystallizes to calcite. The initial formation of ACC may be a first step in the precipitation of calcite under a wide variety of conditions, including geological CO 2 sequestration. amorphous calcium carbonate (ACC) | calorimetry | crystallization enthalpy | sea urchin larval spicules | synthetic and biogenic ACC

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Emergent Nanostructures: Water‐Induced Mesoscale Transformation of Surfactant‐Stabilized Amorphous Calcium Carbonate Nanoparticles in Reverse Microemulsions

Cited by 160 publications

References 37 publications

Higher‐Order Organization by Mesoscale Self‐Assembly and Transformation of Hybrid Nanostructures

Higher‐Order Organization by Mesoscale Self‐Assembly and Transformation of Hybrid Nanostructures

Energetic clues to pathways to biomineralization: Precursors, clusters, and nanoparticles

Transformation and crystallization energetics of synthetic and biogenic amorphous calcium carbonate

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