Spherulites

Shtukenberg, Alexander G.; Punin, Yuri O.; Gunn, Erica; Kahr, Bart

doi:10.1021/cr200297f

Cited by 378 publications

(474 citation statements)

References 346 publications

(701 reference statements)

Supporting

Mentioning

422

Contrasting

Unclassified

Order By: Relevance

“…2,6,7 Received: January 6, 2017 Accepted: May 31, 2017 Published: May 31, 2017 Space-filling is the second key characteristic of spherulites, which distinguishes them from other crystals formed by dendritic or fractal growth. 7,13 To fill space a spherulite must contain crystals oriented in all possible directions, neighboring crystals must be slightly mis-oriented by NCB, therefore the two key characteristics are related to one another.Aragonite grows acicularly, with growth rate along the c-axis 10× greater than along the a-axis. 9 Our hypothesis is that the most efficient way for aragonite to fill-space is to grow all crystals along the fast c-axis, that is, to grow spherulitically.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Spherulitic Growth of Coral Skeletons and Synthetic Aragonite: Nature’s Three-Dimensional Printing

Sun¹,

Marcus

Frazier³

et al. 2017

ACS Nano

View full text Add to dashboard Cite

Coral skeletons were long assumed to have a spherulitic structure, that is, a radial distribution of acicular aragonite (CaCO 3 ) crystals with their c-axes radiating from series of points, termed centers of calcification (CoCs). This assumption was based on morphology alone, not on crystallography. Here we measure the orientation of crystals and nanocrystals and confirm that corals grow their skeletons in bundles of aragonite crystals, with their caxes and long axes oriented radially and at an angle from the CoCs, thus precisely as expected for feather-like or "plumose" spherulites. Furthermore, we find that in both synthetic and coral aragonite spherulites at the nanoscale adjacent crystals have similar but not identical orientations, thus demonstrating by direct observation that even at nanoscale the mechanism of spherulite formation is non-crystallographic branching (NCB), as predicted by theory. Finally, synthetic aragonite spherulites and coral skeletons have similar angle spreads, and angular distances of adjacent crystals, further confirming that coral skeletons are spherulites. This is important because aragonite grows anisotropically, 10 times faster along the c-axis than along the a-axis direction, and spherulites fill space with crystals growing almost exclusively along the c-axis, thus they can fill space faster than any other aragonite growth geometry, and create isotropic materials from anisotropic crystals. Greater space filling rate and isotropic mechanical behavior are key to the skeleton's supporting function and therefore to its evolutionary success. In this sense, spherulitic growth is Nature's 3D printing. KEYWORDS: Ion attachment, crystallization by particle attachment, CPA, biomineralization, PEEM, PIC-mapping, mesocrystal S pherulites are polycrystalline structures in which acicular crystals radiate from a common center and grow approximately synchronously so the final shape of a spherulite resembles a sphere. 1−7 Figure 1 shows two types of spherulites: "spherical spherulite", in which the crystal fibers start from a point, or "plumose spherulite", in which crystal fibers radiate at an angle from the line. 7 Spherulites start forming as an aggregate of parallel acicular crystals termed "fibers", then form a "sheaf of wheat" structure, and with the growth of more fibers eventually become complete spheres. 8 In an ideal spherulite, fibers radiate from the center and contain all possible orientations within the sphere. Since the fast-growing axis in aragonite (CaCO 3 ) is the c-axis, 9 in spherulites each fiber elongation direction coincides with the crystalline c-axis. 10,11 In real spherulites, biogenic 12 and synthetic, 7 the crystal orientations are not perfectly radial nor continuously varying with angle, they deviate slightly from radial and exhibit small but abrupt changes in orientation, termed "branching". In Figure 1 branching angles are smaller than 30°in direction and in crystal lattice orientation. This is distinct from crystallographic branching, which occurs in sno...

show abstract

mentioning

confidence: 99%

“…2,6,7 Coral skeletons are among the most important biominerals because they form coral reefs, the most biodiverse ecosystems in the ocean. These have received increased attention in recent decades because they are threatened by global warming and ocean acidification.…”

mentioning

confidence: 99%

Spherulitic Growth of Coral Skeletons and Synthetic Aragonite: Nature’s Three-Dimensional Printing

Sun¹,

Marcus

Frazier³

et al. 2017

ACS Nano

View full text Add to dashboard Cite

show abstract

“…The formation of spherulites commonly occurs under non-equilibrium conditions. The growth of spherulitic assemblies has been frequently reported to be caused by rapid crystallization from solutions containing high solute concentration or crystallization by solvent evaporation at high temperatures, whereas slow crystallization of the same solutions was reported to lead to the growth of hedrites in many cases 31 . However, we have shown that spherulites can be formed at milder non-equilibrium conditions (in a single step at room temperature and organic solvent-free process) compared to what has been previously claimed to be a mild conditions (temperature of 60 °C) for the formation of spherulites 11,32 .…”

Section: Mechanism Of Spherulitic Formationmentioning

confidence: 99%

“…During the evaporation stage the fate of individual crystals within an aggregate is determined by the crystal orientation with respect to the substrate surface and the growth rates. It has been reported that at a faster growing rate, crystals will be easily oriented to the aggregate interface and the spherulite assembly has a better chance of formation 31 . However, it is crucial to inhibit the interactions between the assembling molecules and the substrate in order to facilitate the molecule grouping from individual crystals to the spherulitic arrangement, especially at lower growing rates under mild nonequilibrium conditions.…”

Section: Mechanism Of Spherulitic Formationmentioning

confidence: 99%

Impact of Substrate Properties on the Formation of Spherulitic Films: A Case Study of Salbutamol Sulfate

Serrano

Mugheirbi

O’Connell

et al. 2016

Crystal Growth & Design

View full text Add to dashboard Cite

Spherulitic assemblies have applications as carriers for drug delivery and as targeting vectors. Presently, the driving force behind the formation of spherulites comprising small drug molecules is not fully understood. Herein, the impact of different substrate types on spherulitic crystallization of salbutamol sulfate (SS) was investigated. Freshly cleaved mica, silicon (111) wafer (SiW), uncoated borosilicate glass (UG), silane coated glass (CG) and stainless steel (MS) were used as substrates. It was demonstrated that the spherulite growth can be controlled via the substrate selection. Spherulite formation was inhibited on hydrophilic substrates, such as mica, possibly due to stronger intermolecular interactions between SS and the substrate than SS-SS interactions. Contact angle measurements established that mica possessed the lowest contact angle (15.1±0.5°) and the values of this parameter increased in the order of UC˂SiW˂CG˂MS. Substrate roughness also played a key role in controlling spherulite formation. SiW, UC and CG had isotropic surfaces with low average roughness, facilitating spherulite formation. Overall, this work demonstrates that it is possible to successfully produce SS spherulites using a single step process at room temperature. Furthermore, the formation of SS spherulites can be tuned by the hydrophobicity of the substrate, an approach that could be applied to assembling spherulites of other small organic molecules. Presently, the driving force behind the formation of spherulites comprising small drug molecules is not fully understood. Herein, the impact of different substrate types on spherulitic crystallization of salbutamol sulfate (SS) was investigated. Freshly cleaved mica, silicon (111) wafer (SiW), uncoated borosilicate glass (UG), silane coated glass (CG) and stainless steel (MS) were used as substrates. It was demonstrated that the spherulite growth can be controlled via the substrate selection. Spherulite formation was inhibited on hydrophilic substrates, such as mica, possibly due to stronger intermolecular interactions between SS and the substrate than SS-SS interactions. Contact angle measurements established that mica possessed the lowest contact angle (15.1±0.5°) and the values of this parameter increased in the order of UC˂SiW˂CG˂MS. Substrate roughness also played a key role in controlling spherulite formation. SiW, UC and CG had isotropic surfaces with low average roughness, facilitating spherulite formation. Overall, this work demonstrates that it is possible to successfully produce SS spherulites using a single step process at room temperature. Furthermore, the formation of SS spherulites can be tuned by the hydrophobicity of the substrate, an approach that could be applied to assembling spherulites of other small organic molecules.

show abstract

“…15,18−23 The "double-leaf" growth is recognized to depend on varies factors such as the number of nucleation sites, structure of the material, and supersaturation. 15 Yet, its microscopic mechanism is still an open question. In experimental work on fluorapatite "double-leaf" spherulites grown in gelatin, electron holography revealed that branching was highly influenced by the distribution of the intrinsic dipole field.…”

mentioning

confidence: 99%

Fabrication and Growth Mechanism of Pumpkin-Shaped Vaterite Hierarchical Structures

Wang

2014

Crystal Growth & Design

View full text Add to dashboard Cite

CaCO3-based biominerals usually possess sophisticated hierarchical structures and promising mechanical properties. Recent researches imply that vaterite may play an important role in the formation of CaCO3-based biominerals. However, as a less common polymorph of CaCO3, the growth mechanism of vaterite remains unclear. Here we report the growth of a pumpkin-shaped vaterite hierarchical structure with a sixfold symmetrical axis and lamellar microstructure. We demonstrate that the growth is controlled by supersaturation and the intrinsic crystallographic anisotropy of vaterite. For the scenario of high supersaturation, the nucleation rate is higher than the lateral extension rate, favoring the “double-leaf” spherulitic growth. Meanwhile, nucleation occurs preferentially in ⟨112̅0⟩ as determined by the crystalline structure of vaterite, modulating the grown products with a hexagonal symmetry. The results are beneficial for an in-depth understanding of the biomineralization of CaCO3. The growth mechanism may also be applicable to interpreting the formation of similar hierarchical structures of other materials.

show abstract

Spherulites

Cited by 378 publications

References 346 publications

Spherulitic Growth of Coral Skeletons and Synthetic Aragonite: Nature’s Three-Dimensional Printing

Spherulitic Growth of Coral Skeletons and Synthetic Aragonite: Nature’s Three-Dimensional Printing

Impact of Substrate Properties on the Formation of Spherulitic Films: A Case Study of Salbutamol Sulfate

Fabrication and Growth Mechanism of Pumpkin-Shaped Vaterite Hierarchical Structures

Contact Info

Product

Resources

About