Local Heating Transforms Amorphous Calcium Carbonate to Single Crystals with Defined Morphologies

Abstract

The use of amorphous calcium carbonate (ACC) as a precursor phase affords organisms with outstanding control over the formation of calcite and aragonite biominerals. Essential to this strategy is that the ACC is maintained within confined volumes in the absence of bulk water. This ensures that the ACC undergoes a pseudomorphic transformation and that the organism can independently control nucleation and growth. However, comparable control has proven hard to achieve in synthetic systems. Here, a straightforward method is demonstrated for controlling the crystallization of ACC thin films in which nucleation is first triggered using a heated probe, and then growth is sustained by incubating the film at a lower temperature. By independently controlling nucleation and growth, sub-millimeter calcite single crystals can be generated when and where it is desired, morphologies ranging from discs to squares to serpentine strips can be created, and arrays of crystals formed. The mechanism and energetics of crystallization of the ACC are studied using in situ transmission electron microscopy and continuity between the ACC and calcite at the growth front is demonstrated. It is envisaged that this method can be applied to the formation of large single crystals of alternative functional materials that form via amorphous precursor phases.

Additive Manufacturing of Porous Biominerals

“…Traditional XRD confirms these results, as shown in Figure S17 (Supporting Information). This result is consistent with results obtained by forming these minerals in bulk, [ 71 ] suggesting that knowhow on polymorphic control of CaCO 3 formation in bulk aqueous solutions can be transferred to our process.…”

Bottling Liquid‐Like Minerals for Advanced Materials Synthesis

“…Crystalline CaCO 3 coatings with (or without) hierarchical ordering, having applications in soil-stabilization, [21] films for biomedical materials, [48] or coatings for oil-water separation [49] iv. Polymer-ACC composite materials, having applications as sustainable "mineral" plastics, [24] protective packaging, [50] or glassy functional materials [25] v. Polymer stabilized ACC materials or coatings, having applications as precursors for single crystals, [37,51] for inorganic monoliths [52] or for thin CaCO 3 films [53] vi. Spherical calcite particles with narrow size distribution, having applications as filler or reinforcing materials [54] or drug delivery materials [55] Our work enables the use of liquid-like precursor phases for material synthesis on application-relevant scales, possessing relevance for use in stone restauration, production of mineral molds, mineral coatings, as well as showing promise to produce mineral materials for construction chemistry, for example, toward the development and improvement of calcium carbonate based, CO 2fixating cements.…”

“…The titration‐based method was also used to estimate the stability of the precursor and tune its stability by adding magnesium ions, while the workability of the product was improved by using superplasticizer. The liquid‐like properties of the precursors synthesized using SCULPT can be used for material synthesis of different kinds of mineral materials with distinct applications, for example, the following: Crystalline, solid CaCO 3 materials, having applications in restoration formulations, [ 46 ] and potential for use in calcium carbonate‐based cements [ 7 ] “Molded” CaCO 3 minerals, having applications as high‐resolution mineral molding formulation or for the synthesis of biomimetic materials [ 15,16,47 ] Crystalline CaCO 3 coatings with (or without) hierarchical ordering, having applications in soil‐stabilization, [ 21 ] films for biomedical materials, [ 48 ] or coatings for oil‐water separation [ 49 ] Polymer‐ACC composite materials, having applications as sustainable “mineral” plastics, [ 24 ] protective packaging, [ 50 ] or glassy functional materials [ 25 ] Polymer stabilized ACC materials or coatings, having applications as precursors for single crystals, [ 37,51 ] for inorganic monoliths [ 52 ] or for thin CaCO 3 films [ 53 ] Spherical calcite particles with narrow size distribution, having applications as filler or reinforcing materials [ 54 ] or drug delivery materials [ 55 ] …”

“…Polymer stabilized ACC materials or coatings, having applications as precursors for single crystals, [ 37,51 ] for inorganic monoliths [ 52 ] or for thin CaCO 3 films [ 53 ]…”

Polyamines Promote Aragonite Nucleation and Generate Biomimetic Structures

“…The ability of organisms to achieve selectivity over calcite and aragonite, and in some cases, even switch between the two, [ 1 ] is typically attributed to specific macromolecules, [ 5,6 ] or combinations of macromolecules, [ 7 ] which may select for each polymorph. Magnesium ions also promote the formation of magnesian calcite and ultimately aragonite as the Mg/Ca ratio increases [ 8,9 ] and may contribute to aragonite formation in vivo. [ 10 ] However, despite a report of switching between calcite and aragonite using biomacromolecules extracted from aragonite or calcite, [ 5 ] few have succeeded in generating aragonite using single proteins or protein fragments derived from aragonite [ 11 ] without combining the macromolecules with more complex environments such as a chitin substrate, [ 12,13 ] an insoluble β ‐chitin/silk‐fibroin matrix, [ 6 ] or the addition of magnesium ions.…”