Now You See Them

Meldrum, Fiona C.; Sear, Richard P.

doi:10.1126/science.1167221

Cited by 104 publications

(83 citation statements)

References 14 publications

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“…Once the island has fully crystallized and adopts the calcite structure, it does not grow further in height within the timescale of our experiments, which is consistent with expectation that the most stable surface of a given mineral (here the ð10 1 4Þ surface for calcite) grows the slowest. Non-classical pathways of crystallization via the formation of amorphous precursors have been reported, for example, for growth of biogenic calcite in the presence of a calcite seed crystal (Weiner et al, 2005;Politi et al, 2008;Killian et al, 2009), for calcite growth templated by self-assembled monolayers (Freeman et al, 2008;Pouget et al, 2009), and for homogeneous nucleation and growth of calcite in aqueous solutions (Gebauer et al, 2008;Meldrum and Sear, 2008;Raiteri and Gale, 2011). This idea is also supported by the Ostwald-Lussac law of phases, which states that the free energy barrier for nucleation leading to a more disordered state is less than the one leading to a more crystalline state (Nancollas, 1982).…”

Section: [Cd 2+ ]-Dependent Heteroepitaxial Growth Mechanismsmentioning

confidence: 99%

Kinetics and mechanisms of cadmium carbonate heteroepitaxial growth at the calcite (101¯4) surface

Xu¹,

Kovařík²,

Arey³

et al. 2014

Geochimica et Cosmochimica Acta

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Elucidating the kinetics and mechanisms of heteroepitaxial nucleation and growth at mineral-water interfaces is essential to understanding surface reactivity in geochemical systems. In the present work, the formation of heteroepitaxial cadmium carbonate coatings at calcite-water interfaces was investigated by exposing calcite ð10 1 4Þ surfaces to Cd-bearing aqueous solutions. In situ atomic force microscopy (AFM) was employed as the primary technique. The AFM results indicate that the heteroepitaxial growth of cadmium carbonate proceeds via three different mechanisms depending on the initial supersaturation of the aqueous solution: advancement of existing steps, nucleation and growth of three-dimensional (3D) islands, and nucleation and spread of two-dimensional (2D) nuclei. The 3D islands and 2D nuclei exhibit different morphologies and growth kinetics. The effects of supersaturation on heteroepitaxial growth mechanisms can be interpreted in terms of the free energy barrier for nucleation. At low initial supersaturation, where 3D nucleation dominates, it is hypothesized, from the growth rate and morphology of the 3D islands observed with AFM, that the crystallization of the overgrowth follows a non-classical pathway involving the formation of a surface precursor that is not fully crystalline, whereas high supersaturation favors the formation of crystalline 2D nuclei whose morphology is based on the atomic structure of the calcite substrate. Cross-sectional transmission electron microscopy (TEM) images reveal that the atomic structure of the interface between the cadmium carbonate coating and calcite shows perfect, dislocation-free epitaxy.

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Section: [Cd 2+ ]-Dependent Heteroepitaxial Growth Mechanismsmentioning

confidence: 99%

Kinetics and mechanisms of cadmium carbonate heteroepitaxial growth at the calcite (101¯4) surface

Xu¹,

Kovařík²,

Arey³

et al. 2014

Geochimica et Cosmochimica Acta

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“…The characterization of these processes and a quantitative assessment of the crystallization pathways of Dy-bearing carbonates precipitated from solution, is not just a crucial missing link for their potential industrial applications (Yan et al 2011), but such ''green'' low temperature aqueous solvent carbonate crystallization reactions can also contribute to the debate about the validity of the classical nucleation theory in the carbonate system overall (Meldrum and Sear 2008).…”

Section: Introductionmentioning

confidence: 99%

Amorphous dysprosium carbonate: characterization, stability, and crystallization pathways

et al. 2013

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The crystallization of amorphous dysprosium carbonate (ADC) has been studied in air (21-750°C) and in solution (21-250°C). This poorly ordered precursor, Dy 2 (CO 3 ) 3 Á4H 2 O, was synthesized in solution at ambient temperature. Its properties and crystallization pathways were studied by powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning and transmission electron microscopy, thermogravimetric analysis, and magnetic techniques. ADC consists of highly hydrated spherical nanoparticles of 10-20 nm diameter that are exceptionally stable under dry treatment at ambient and high temperatures (\550°C). However, ADC transforms in solution to a variety of Dy-carbonates, depending on the temperature and reaction times. The transformation sequence is (a) poorly crystalline metastable tengerite-type phase, Dy 2 (CO 3 ) 3 Á2-3H 2 O; and (b) the orthorhombic kozoite-type phase DyCO 3 (OH) at 165°C after prolonged times (15 days) or faster (12 h) at 220°C. Both the amorphous phase and the kozoite-type phase DyCO 3 (OH) are paramagnetic in the range of temperatures measured from 1.8 to 300 K.

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“…8,9,14,[25][26][27] In contrast to the classical crystallization pathways, the nonclassical crystallization route involves mesoscopic transformations of self-assembled, metastable, or amorphous precursor particles into nanoparticulate superstructures. 28,29 Because this process assembles materials from the nanoscopic scale to large sizes, it is also called the bottom-up strategy. 8,30 Many previous experiments and studies have shown that biomineralization is a bottom-up process based on the theory of nonclassical crystallization.…”

Section: Introductionmentioning

confidence: 99%

Synergistic intrafibrillar/extrafibrillar mineralization of collagen scaffolds based on a biomimetic strategy to promote the regeneration of bone defects

Wang¹,

Manh²,

Wang³

et al. 2016

IJN

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The mineralization of collagen scaffolds can improve their mechanical properties and biocompatibility, thereby providing an appropriate microenvironment for bone regeneration. The primary purpose of the present study is to fabricate a synergistically intra- and extrafibrillar mineralized collagen scaffold, which has many advantages in terms of biocompatibility, biomechanical properties, and further osteogenic potential. In this study, mineralized collagen scaffolds were fabricated using a traditional mineralization method (ie, immersed in simulated body fluid) as a control group and using a biomimetic method based on the polymer-induced liquid precursor process as an experimental group. In the polymer-induced liquid precursor process, a negatively charged polymer, carboxymethyl chitosan (CMC), was used to stabilize amorphous calcium phosphate (ACP) to form nanocomplexes of CMC/ACP. Collagen scaffolds mineralized based on the polymer-induced liquid precursor process were in gel form such that nanocomplexes of CMC/ACP can easily be drawn into the interstices of the collagen fibrils. Scanning electron microscopy and transmission electron microscopy were used to examine the porous micromorphology and synergistic mineralization pattern of the collagen scaffolds. Compared with simulated body fluid, nanocomplexes of CMC/ACP significantly increased the modulus of the collagen scaffolds. The results of in vitro experiments showed that the cell count and differentiated degrees in the experimental group were higher than those in the control group. Histological staining and micro-computed tomography showed that the amount of new bone regenerated in the experimental group was larger than that in the control group. The biomimetic mineralization will assist us in fabricating a novel collagen scaffold for clinical applications.

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Now You See Them

Cited by 104 publications

References 14 publications

Kinetics and mechanisms of cadmium carbonate heteroepitaxial growth at the calcite (101¯4) surface

Kinetics and mechanisms of cadmium carbonate heteroepitaxial growth at the calcite (101¯4) surface

Amorphous dysprosium carbonate: characterization, stability, and crystallization pathways

Synergistic intrafibrillar/extrafibrillar mineralization of collagen scaffolds based on a biomimetic strategy to promote the regeneration of bone defects

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