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Open Access
Abstract: Incorporating additives within host single crystals is an effective strategy for producing composite materials with tunable mechanical, magnetic and optical properties. The type of guest materials that can be occluded can be limited, however, as incorporation is a complex process depending on many factors including binding of the additive to the crystal surface, the rate of crystal growth and the stability of the additives in the crystallisation solution. In particular, the size of occluded guests has been restricted to a few angstroms, as for single molecules, to a few hundred nanometers, as for polymer vesicles and particles. Here, we present a synthetic approach for occluding micrometer-scale objects, including high-complexity unicellular organisms and synthetic hollow calcite spheres within calcite single crystals. Both of these objects can transport functional additives, including organic molecules and nanoparticles that would not otherwise occlude within calcite. Therefore, this method constitutes a generic approach using calcite as a delivery system for active compounds, while providing them with effective protection against environmental factors that could cause degradation.
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Dec 2021
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[27557]
Abstract: Soluble additives are widely used to control crystallization processes, modifying the morphologies, sizes, polymorphs, and physical properties of the product crystals. Here, a simple and versatile strategy is shown to significantly enhance the potency of soluble additives, ranging from ions and amino acids to large dye molecules, enabling them to be effective even at low concentrations. Addition of small amounts of miscible organic co-solvents to an aqueous crystallization solution can yield enhanced morphological changes and an order of magnitude increase of additive incorporation within single crystals─a level that cannot be achieved in pure aqueous solutions at any additive concentration. The generality of this strategy is demonstrated by application to crystals of calcium carbonate, manganese carbonate, and strontium sulfate, with a more pronounced effect observed for co-solvents with lower dielectric constants and polarities, indicating a general underlying mechanism that alters water activity. This work increases the understanding of additive/crystal interactions and may see great application in industrial-scale crystal synthesis.
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Nov 2021
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I13-2-Diamond Manchester Imaging
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Clara
Anduix-Canto
,
Mark A.
Levenstein
,
Yi-Yeoun
Kim
,
Jose R. A.
Godinho
,
Alexander N.
Kulak
,
Carlos
Gonzalez Nino
,
Philip J.
Withers
,
Jonathan P.
Wright
,
Nikil
Kapur
,
Hugo K.
Christenson
,
Fiona C.
Meldrum
Diamond Proposal Number(s):
[13578, 17314]
Open Access
Abstract: Characterizing the pathways by which crystals form remains a significant challenge, particularly when multiple pathways operate simultaneously. Here, an imaging-based strategy is introduced that exploits confinement effects to track the evolution of a population of crystals in 3D and to characterize crystallization pathways. Focusing on calcium sulfate formation in aqueous solution at room temperature, precipitation is carried out within nanoporous media, which ensures that the crystals are fixed in position and develop slowly. The evolution of their size, shape, and polymorph can then be tracked in situ using synchrotron X-ray computed tomography and diffraction computed tomography without isolating and potentially altering the crystals. The study shows that bassanite (CaSO4 0.5H2O) forms via an amorphous precursor phase and that it exhibits long-term stability in these nanoscale pores. Further, the thermodynamically stable phase gypsum (CaSO4 2H2O) can precipitate by different pathways according to the local physical environment. Insight into crystallization in nanoconfinement is also gained, and the crystals are seen to grow throughout the nanoporous network without causing structural damage. This work therefore offers a novel strategy for studying crystallization pathways and demonstrates the significant impact of confinement on calcium sulfate precipitation, which is relevant to its formation in many real-world environments.
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Sep 2021
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I11-High Resolution Powder Diffraction
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Mark A.
Levenstein
,
Yi-Yeoun
Kim
,
Liam
Hunter
,
Clara
Anduix-Canto
,
Carlos
Gonzalez Nino
,
Sarah J.
Day
,
Shunbo
Li
,
William J.
Marchant
,
Phillip A.
Lee
,
Chiu C.
Tang
,
Manfred
Burghammer
,
Fiona C.
Meldrum
,
Nikil
Kapur
Diamond Proposal Number(s):
[10425, 12352]
Open Access
Abstract: The clean and reproducible conditions provided by microfluidic devices are ideal sample environments for in situ analyses of chemical and biochemical reactions and assembly processes. However, the small size of microchannels makes investigating the crystallization of poorly soluble materials on-chip challenging due to crystal nucleation and growth that result in channel fouling and blockage. Here, we demonstrate a reusable insert-based microfluidic platform for serial X-ray diffraction analysis and examine scale formation in response to continuous and segmented flow configurations across a range of temperatures. Under continuous flow, scale formation on the reactor walls begins almost immediately on mixing of the crystallizing species, which over time results in occlusion of the channel. Depletion of ions at the start of the channel results in reduced crystallization towards the end of the channel. Conversely, segmented flow can control crystallization, so it occurs entirely within the droplet. Consequently, the spatial location within the channel represents a temporal point in the crystallization process. Whilst each method can provide useful crystallographic information, time-resolved information is lost when reactor fouling occurs and changes the solution conditions with time. The flow within a single device can be manipulated to give a broad range of information addressing surface interaction or solution crystallization.
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Jul 2020
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I11-High Resolution Powder Diffraction
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Mark A.
Levenstein
,
Lois E.
Wayment
,
C. Daniel
Scott
,
Ruth A.
Lunt
,
Pierre-Baptiste
Flandrin
,
Sarah
Day
,
Chiu
Tang
,
Chick C.
Wilson
,
Fiona C.
Meldrum
,
Nikil
Kapur
,
Karen
Robertson
Diamond Proposal Number(s):
[14807, 18771, 18405]
Abstract: Understanding the transitions between polymorphs is essential in the development of strategies for manufacturing and max-imizing the efficiency of pharmaceuticals. However, this can be extremely challenging: crystallization can be influenced by subtle changes in environment such as temperature and mixing intensity or even imperfections in the crystallizer walls. Here, we highlight the importance of in situ measurements in understanding crystallization mechanisms, where a segmented flow crystallizer was used to study the crystallization of the pharmaceuticals urea:barbituric acid (UBA) and carbamazepine (CBZ). The reactor provides highly reproducible reaction conditions, while in situ synchrotron powder X-ray diffraction (PXRD) enables us to monitor the evolution of this system. UBA has two polymorphs of almost equivalent free-energy and so is typically obtained as a polymorphic mixture. In situ PXRD uncovered a progression of polymorphs from UBA III to the thermodynamic polymorph UBA I, where different positions along the length of the tubular flow crystallizer correspond to different reaction times. Addition of UBA I seed crystals modified this pathway such that only UBA I was observed throughout, while transformation from UBA III into UBA I still occurred in the presence of UBA III seeds. Information re-garding the mixing-dependent kinetics of the CBZ form II to III transformation was also uncovered in a series of seeded and unseeded flow crystallization runs, despite atypical habit expression. These results illustrate the importance of coupling controlled reaction environments with in situ XRD to study the phase relationships in polymorphic materials.
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May 2020
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I22-Small angle scattering & Diffraction
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Open Access
Abstract: This work shows that highly uniform worm micelles formed by polymerisation induced self-assembly can be obtained via simple post-synthesis sonication. Importantly, this straightforward and versatile strategy yields exceptionally monodisperse worms with tunable aspect ratios ranging from 7.2 to 17.6 by simply changing the sonication time.
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May 2020
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I11-High Resolution Powder Diffraction
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Yi-Yeoun
Kim
,
Robert
Darkins
,
Alexander
Broad
,
Alexander N.
Kulak
,
Mark A.
Holden
,
Ouassef
Nahi
,
Steven P.
Armes
,
Chiu C.
Tang
,
Rebecca F.
Thompson
,
Frederic
Marin
,
Dorothy M.
Duffy
,
Fiona C.
Meldrum
Open Access
Abstract: Acidic macromolecules are traditionally considered key to calcium carbonate biomineralisation and have long been first choice in the bio-inspired synthesis of crystalline materials. Here, we challenge this view and demonstrate that low-charge macromolecules can vastly outperform their acidic counterparts in the synthesis of nanocomposites. Using gold nanoparticles functionalised with low charge, hydroxyl-rich proteins and homopolymers as growth additives, we show that extremely high concentrations of nanoparticles can be incorporated within calcite single crystals, while maintaining the continuity of the lattice and the original rhombohedral morphologies of the crystals. The nanoparticles are perfectly dispersed within the host crystal and at high concentrations are so closely apposed that they exhibit plasmon coupling and induce an unexpected contraction of the crystal lattice. The versatility of this strategy is then demonstrated by extension to alternative host crystals. This simple and scalable occlusion approach opens the door to a novel class of single crystal nanocomposites.
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Dec 2019
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I11-High Resolution Powder Diffraction
I22-Small angle scattering & Diffraction
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Mark A.
Levenstein
,
Clara
Anduix-Canto
,
Yi-Yeoun
Kim
,
Mark A.
Holden
,
Carlos
Gonzalez Nino
,
David C.
Green
,
Stephanie E.
Foster
,
Alexander N.
Kulak
,
Lata
Govada
,
Naomi E.
Chayen
,
Sarah J.
Day
,
Chiu C.
Tang
,
Britta
Weinhausen
,
Manfred
Burghammer
,
Nikil
Kapur
,
Fiona C.
Meldrum
Diamond Proposal Number(s):
[10425, 12352, 17729]
Abstract: The ability to control crystallization reactions is required in a vast range of processes including the production of functional inorganic materials and pharmaceuticals and the prevention of scale. However, it is currently limited by a lack of understanding of the mechanisms underlying crystal nucleation and growth. To address this challenge, it is necessary to carry out crystallization reactions in well‐defined environments, and ideally to perform in situ measurements. Here, a versatile microfluidic synchrotron‐based technique is presented to meet these demands. Droplet microfluidic‐coupled X‐ray diffraction (DMC‐XRD) enables the collection of time‐resolved, serial diffraction patterns from a stream of flowing droplets containing growing crystals. The droplets offer reproducible reaction environments, and radiation damage is effectively eliminated by the short residence time of each droplet in the beam. DMC‐XRD is then used to identify effective particulate nucleating agents for calcium carbonate and to study their influence on the crystallization pathway. Bioactive glasses and a model material for mineral dust are shown to significantly lower the induction time, highlighting the importance of both surface chemistry and topography on the nucleating efficiency of a surface. This technology is also extremely versatile, and could be used to study dynamic reactions with a wide range of synchrotron‐based techniques.
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Mar 2019
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I13-1-Coherence
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Diamond Proposal Number(s):
[7654, 7277]
Open Access
Abstract: Soluble additives provide a versatile strategy for controlling crystallization processes, enabling selection of properties including crystal sizes, morphologies, and structures. The additive species can also be incorporated within the crystal lattice, leading for example to enhanced mechanical properties. However, while many techniques are available for analyzing particle shape and structure, it remains challenging to characterize the structural inhomogeneities and defects introduced into individual crystals by these additives, where these govern many important material properties. Here, we exploit Bragg coherent diffraction imaging to visualize the effects of soluble additives on the internal structures of individual crystals on the nanoscale. Investigation of bio-inspired calcite crystals grown in the presence of lysine or magnesium ions reveals that while a single dislocation is observed in calcite crystals grown in the presence of lysine, magnesium ions generate complex strain patterns. Indeed, in addition to the expected homogeneous solid solution of Mg ions in the calcite lattice, we observe two zones comprising alternating lattice contractions and relaxation, where comparable alternating layers of high magnesium calcite have been observed in many magnesium calcite biominerals. Such insight into the structures of nanocomposite crystals will ultimately enable us to understand and control their properties.
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Nov 2018
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B16-Test Beamline
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Diamond Proposal Number(s):
[14790]
Abstract: The topic of calcite and aragonite polymorphism attracts enormous interest from fields including biomineralization and paleogeochemistry. While aragonite is only slightly less thermodynamically stable than calcite under ambient conditions, it typically only forms as a minor product in additive-free solutions at room temperature. However, aragonite is an abundant biomineral, and certain organisms can selectively generate calcite and aragonite. This fascinating behavior has been the focus of decades of research, where this has been driven by a search for specific organic macromolecules that can generate these polymorphs. However, despite these efforts, we still have a poor understanding of how organisms achieve such selectivity. In this work, we consider an alternative possibility and explore whether the confined volumes in which all biomineralization occurs could also influence polymorph. Calcium carbonate was precipitated within the cylindrical pores of track-etched membranes, where these enabled us to systematically investigate the relationship between the membrane pore diameter and polymorph formation. Aragonite was obtained in increasing quantities as the pore size was reduced, such that oriented single crystals of aragonite were the sole product from additive-free solutions in 25-nm pores and significant quantities of aragonite formed in pores as large as 200 nm in the presence of low concentrations of magnesium and sulfate ions. This effect can be attributed to the effect of the pore size on the ion distribution, which becomes of increasing importance in small pores. These intriguing results suggest that organisms may exploit confinement effects to gain control over crystal polymorph.
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Jul 2018
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