Combined Synchrotron XRD/Raman Measurements: <i>In Situ</i> Identification of Polymorphic Transitions during Crystallization Processes

Klimakow, Maria; Leiterer, Jork; Kneipp, Janina; Rössler, E. A.; Panne, Ulrich; Rademann, Klaus; Emmerling, Franziska

doi:10.1021/la100540q

Cited by 36 publications

(30 citation statements)

References 25 publications

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“…[84,116,117] The droplets are maintained under conditions of controlled humidity and temperature, and crystallization can be induced through a change of temperature [118,119] (for example to investigate a freezing transition) or through evaporation. [116,117,[120][121][122] A facile exchange of gases occurs between the droplet and its environment, and evaporation can be controlled leading to a concomitant increase in supersaturation and resultant crystallization. .…”

Section: Levitated Dropletsmentioning

confidence: 99%

“…These systems can be used to study nucleation, where techniques such as optical microscopy, [123] and angle-resolved light scattering [118][119][120] allow nucleation rates to be determined. The entire crystallization pathway occurring within individual droplets can also be characterized using in situ analytical techniques including IR, [124] UV-vis spectroscopy, [125] Raman spectroscopy and synchrotron X-ray diffraction [116,122,126] and images of the crystals forming within the droplets can be recorded using a high-speed camera. [121,124] This is particularly attractive for compounds that are polymorphic, or that form via metastable phases, and enables the entire process-from the evaporation of the solvent, to the formation of transient metastable and their ultimate transformation into stable crystalline forms-to be characterized.…”

Section: Levitated Dropletsmentioning

confidence: 99%

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Crystallization in Confinement

2020

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Many crystallization processes of great importance, including frost heave, biomineralization, the synthesis of nanomaterials, and scale formation, occur in small volumes rather than bulk solution. Here, the influence of confinement on crystallization processes is described, drawing together information from fields as diverse as bioinspired mineralization, templating, pharmaceuticals, colloidal crystallization, and geochemistry. Experiments are principally conducted within confining systems that offer well‐defined environments, varying from droplets in microfluidic devices, to cylindrical pores in filtration membranes, to nanoporous glasses and carbon nanotubes. Dramatic effects are observed, including a stabilization of metastable polymorphs, a depression of freezing points, and the formation of crystals with preferred orientations, modified morphologies, and even structures not seen in bulk. Confinement is also shown to influence crystallization processes over length scales ranging from the atomic to hundreds of micrometers, and to originate from a wide range of mechanisms. The development of an enhanced understanding of the influence of confinement on crystal nucleation and growth will not only provide superior insight into crystallization processes in many real‐world environments, but will also enable this phenomenon to be used to control crystallization in applications including nanomaterial synthesis, heavy metal remediation, and the prevention of weathering.

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Section: Levitated Dropletsmentioning

confidence: 99%

Section: Levitated Dropletsmentioning

confidence: 99%

Crystallization in Confinement

2020

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“…Motivated by these questions and technical challenges, we have developed an instrument that integrates a containerless device based on the electrostatic levitation (ESL) with in situ micro-Raman and X-ray scattering apparatus. Although there have been previous efforts to combine levitation techniques [acoustic (27,28) and electrodynamic levitation (29,30)], various technical limitations such as the presence of strong acoustic pressures or very small sample sizes may have hindered direct observation of the spontaneous nucleation at the deepest level of supersaturation.…”

Section: Significancementioning

confidence: 99%

Multiple pathways of crystal nucleation in an extremely supersaturated aqueous potassium dihydrogen phosphate (KDP) solution droplet

Lee

et al. 2016

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

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Solution studies have proposed that crystal nucleation can take more complex pathways than previously expected in classical nucleation theory, such as formation of prenucleation clusters or densified amorphous/liquid phases. These findings show that it is possible to separate fluctuations in the different order parameters governing crystal nucleation, that is, density and structure. However, a direct observation of the multipathways from aqueous solutions remains a great challenge because heterogeneous nucleation sites, such as container walls, can prevent these paths. Here, we demonstrate the existence of multiple pathways of nucleation in highly supersaturated aqueous KH 2 PO 4 (KDP) solution using the combination of a containerless device (electrostatic levitation), and in situ micro-Raman and synchrotron X-ray scattering. Specifically, we find that, at an unprecedentedly deep level of supersaturation, a highconcentration KDP solution first transforms into a metastable crystal before reaching stability at room temperature. However, a low-concentration solution, with different local structures, directly transforms into the stable crystal phase. These apparent multiple pathways of crystallization depend on the degree of supersaturation.multipath nucleation | liquid-droplet levitation | supersaturation | in situ X-ray diffraction | in situ micro-Raman spectroscopy N ucleation is the first step toward crystallization, in which atoms or particles aggregate to form clusters in a metastable liquid, called crystal nuclei. The crystal nuclei in metastable liquid grow continuously if their size exceeds a critical limit, and are subsequently stabilized. Based on the classical nucleation theory (CNT) (1, 2), nucleation is mainly governed by two factors, that is, interfacial free energy and volume Gibbs free energy (or chemical potential) between liquid and crystal phases. Although the volume Gibbs free energy acts to stabilize the crystal nuclei, the interfacial free energy works as an energy barrier preventing the formation of the nuclei. If the crystal-liquid interfacial free energy creates a sufficiently high energy barrier, the liquid can be supercooled, supersaturated, or even supercompressed. In case of liquid metals (3-6), the crystal-liquid interfacial free energy arises from configurational entropy differences between crystal and liquid. That is, the greater difference in local structural orderings between crystal and liquid phases results in higher interfacial free energy, which consequently leads to a higher nucleation barrier and thus deeper supercooling. This concept has been verified in various metallic systems for elements (7) and many alloys (8-12). However, many experimental and theoretical investigations have raised questions that CNT may not be adequate to describe the initial nucleation processes in biomaterials (13-17) and minerals (18)(19)(20)(21)(22)(23)(24)(25)(26).Recently, an alternate nucleation mechanism, called multipathway nucleation (or crystallization) (13-23, 25, 26), has been proposed fo...

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“…The ROY molecules Using the tandem approach with acoustic levitation we succeeded also in elucidating the crystallization process of the pharmaceutical nifedipine from different organic solvents. Different crystallization routes were discovered depending on the solvent (Dichlormethane (DCM), ACN, MeOH, acetone, EtOH) [45]. Nifedipine has three known crystalline modification: α, β, and γ [38][39][40].…”

Section: Compoundmentioning

confidence: 99%

Control of organic polymorph formation: crystallization pathways in acoustically levitated droplets

Nguyen

Roessler

Rademann

et al. 2016

Zeitschrift Für Kristallographie - Crystalline Materials

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Abstract:Theoretical and experimental studies indicate that crystal nucleation can take more complex pathways than expected on the ground of the classical nucleation theory. Among these pathways are the formation of prenucleation clusters and amorphous precursor phases. A direct in situ observation of the different pathways of nucleation from solution is challenging since the paths can be influenced by heterogeneous nucleation sites, such as container walls. Here, we provide insights into the crystallization process using the in situ combination of an acoustic levitator, Raman spectroscopy, and X-ray scattering. The contactless sample holder enables the observation of homogeneous crystallization processes and the detection of intermediates and final crystalline forms. We provide evidence for the existence of multiple pathways of nucleation based on the investigation of the crystallization of organic molecules from different solvents. Starting from a diluted solution, a supersaturation is reached during the experiment due to the evaporation of the solvent. The highly supersaturated solution reveals different pathways of crystallization. Depending on the degree of supersaturation either the thermodynamically stable or the metastable crystal form is observed.

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Combined Synchrotron XRD/Raman Measurements: In Situ Identification of Polymorphic Transitions during Crystallization Processes

Cited by 36 publications

References 25 publications

Crystallization in Confinement

Crystallization in Confinement

Multiple pathways of crystal nucleation in an extremely supersaturated aqueous potassium dihydrogen phosphate (KDP) solution droplet

Control of organic polymorph formation: crystallization pathways in acoustically levitated droplets

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