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Crystal Growth & Design

Joshua D Hartman, Graeme M Day, Gregory J O Beran
Chemical shift prediction plays an important role in the determination or validation of crystal structures with solid-state nuclear magnetic resonance (NMR) spectroscopy. One of the fundamental theoretical challenges lies in discriminating variations in chemical shifts resulting from different crystallographic environments. Fragment-based electronic structure methods provide an alternative to the widely used plane wave gauge-including projector augmented wave (GIPAW) density functional technique for chemical shift prediction...
November 2, 2016: Crystal Growth & Design
Damiano Genovese, Marco Montalti, Fermín Otálora, Jaime Gómez-Morales, María Sancho-Tomás, Giuseppe Falini, Juan Manuel García-Ruiz
The molecular structure of the units that get incorporated into the nuclei of the crystalline phase and sustain their growth is a fundamental issue in the pathway from a supersaturated solution to the formation of crystals. Using a fluorescent dye we have recorded the variation of the pH value in time along a gel where CaCl2 and NaHCO3 counter-diffuse to crystallize CaCO3. The same pH-space-time distribution maps were also computationally obtained using a chemical speciation code (phreeqc). Using data arising from this model we investigated the space-time evolution of the activity of the single species (ions and ion pairs) involved in the crystallization process...
August 3, 2016: Crystal Growth & Design
Magdalena Truger, Otello M Roscioni, Christian Röthel, Dominik Kriegner, Clemens Simbrunner, Rizwan Ahmed, Eric D Głowacki, Josef Simbrunner, Ingo Salzmann, Anna Maria Coclite, Andrew O F Jones, Roland Resel
The appearance of surface-induced phases of molecular crystals is a frequently observed phenomenon in organic electronics. However, despite their fundamental importance, the origin of such phases is not yet fully resolved. The organic molecule 6,6'-dibromoindigo (Tyrian purple) forms two polymorphs within thin films. At growth temperatures of 150 °C, the well-known bulk structure forms, while at a substrate temperature of 50 °C, a surface-induced phase is observed instead. In the present work, the crystal structure of the surface-induced polymorph is solved by a combined experimental and theoretical approach using grazing incidence X-ray diffraction and molecular dynamics simulations...
July 6, 2016: Crystal Growth & Design
Paul Christian, Christian Röthel, Martin Tazreiter, Andreas Zimmer, Ingo Salzmann, Roland Resel, Oliver Werzer
Amorphous films of the anticonvulsant drug carbamazepine are easily accessible by various methods, while the crystallization into specific polymorphs represents a challenging and time-consuming task. In this work, the crystallization of drop cast carbamazepine at silica surfaces is investigated by atomic force microscopy and both in situ and ex situ grazing incidence X-ray diffraction. The pristine films grow with low crystallization rates into a triclinic polymorph, exhibiting poor orientational order within films...
May 4, 2016: Crystal Growth & Design
Rebecca D Sandlin, Kim Y Fong, Renata Stiebler, Christopher P Gulka, Jenny E Nesbitt, Matheus P Oliveira, Marcus F Oliveira, David W Wright
Hemozoin is a unique biomineral that results from the sequestration of toxic free heme liberated as a consequence of hemoglobin degradation in the malaria parasite. Synthetic neutral lipid droplets (SNLDs) and phospholipids were previously shown to support the rapid formation of β-hematin, abiological hemozoin, under physiologically relevant pH and temperature, though the mechanism by which heme crystallization occurs remains unclear. Detergents are particularly interesting as a template because they are amphiphilic molecules that spontaneously organize into nanostructures and have been previously shown to mediate β-hematin formation...
May 4, 2016: Crystal Growth & Design
Eugenia Peresypkina, Alexander Virovets, Manfred Scheer
For the first time, the concept of supramolecular synthons was applied to giant rigid superspheres based on pentaphosphaferrocene [Cp(R)Fe(η(5)-P5)] (R = Me, Et) and Cu(I) halides, which reach 2.1-3.0 nm in diameter. Two supramolecular synthons, σ-π and π-π, are discovered based on halogen···Cp(R) and Cp*···Cp* specific interactions, respectively. The geometry of the synthons is reproducible in a series of crystal structures of various supramolecules. The σ-π synthon alone is realized more frequently for Br-containing superspheres...
April 6, 2016: Crystal Growth & Design
Tongtong Zhu, Tao Ding, Fengzai Tang, Yisong Han, Muhammad Ali, Tom Badcock, Menno J Kappers, Andrew J Shields, Stoyan K Smoukov, Rachel A Oliver
Non- and semipolar GaN have great potential to improve the efficiency of light emitting devices due to much reduced internal electric fields. However, heteroepitaxial GaN growth in these crystal orientations suffers from very high dislocation and stacking faults densities. Here, we report a facile method to obtain low defect density non- and semipolar heteroepitaxial GaN via selective area epitaxy using self-assembled multilayers of silica nanospheres (MSN). Nonpolar (11-20) and semipolar (11-22) GaN layers with high crystal quality have been achieved by epitaxial integration of the MSN and a simple one-step overgrowth process, by which both dislocation and basal plane stacking fault densities can be significantly reduced...
February 3, 2016: Crystal Growth & Design
Mosè Casalegno, Massimo Moret, Roland Resel, Guido Raos
2,2':6',2″-Ternaphthalene (NNN) is a novel, blue-emitting material, suitable for preparation of organic light-emitting diodes. Its crystal structure has been solved recently, but its thermal behavior and surface properties have not yet been explored, partly due to the difficulty in obtaining high quality crystals. In the present study we use classical molecular dynamics to investigate the thermal behavior of bulk and (001) surfaces of NNN. Our bulk simulations indicate the occurrence of a phase transition at about 600 K...
January 6, 2016: Crystal Growth & Design
Andrey Prokofiev, Robert Svagera, Monika Waas, Matthias Weil, Johannes Bernardi, Silke Paschen
Type-I clathrates possess extremely low thermal conductivities, a property that makes them promising materials for thermoelectric applications. The incorporation of cerium into one such clathrate has recently been shown to lead to a drastic enhancement of the thermopower, another property determining the thermoelectric efficiency. Here we explore the mechanism of the incorporation of rare earth elements into type-I clathrates. Our investigation of the crystal growth and the composition of the phase Ba8-x RE x TM y Si46-y (RE = rare earth element; TM = Au, Pd, Pt) reveals that the RE content x is mainly governed by two factors, the free cage space and the electron balance...
January 6, 2016: Crystal Growth & Design
Doyoon Kim, Byeongdu Lee, Stavros Thomopoulos, Young-Shin Jun
We revealed that nucleation sites within collagen fibrils determined pathways for calcium phosphate (CaP) nucleation and its transformation, from amorphous species to crystalline plates, during the biomineralization process. Using in situ small-angle X-ray scattering (SAXS), we examined the nucleation and growth of CaP within collagen matrices and elucidated how a nucleation inhibitor, polyaspartic acid (pAsp), governs mineralization kinetics and pathways at multiple length scales. Mineralization without pAsp led initially to spherical aggregates of CaP in the entire extrafibrillar spaces...
2016: Crystal Growth & Design
Bahige G Abdallah, Shatabdi Roy-Chowdhury, Raimund Fromme, Petra Fromme, Alexandra Ros
Protein crystallization is a major bottleneck of structure determination by X-ray crystallography, hampering the process by years in some cases. Numerous matrix screening trials using significant amounts of protein are often applied, while a systematic approach with phase diagram determination is prohibited for many proteins that can only be expressed in small amounts. Here, we demonstrate a microfluidic nanowell device implementing protein crystallization and phase diagram screening using nanoscale volumes of protein solution per trial...
2016: Crystal Growth & Design
Daniel Jacobsson, Fangfang Yang, Karla Hillerich, Filip Lenrick, Sebastian Lehmann, Dominik Kriegner, Julian Stangl, L Reine Wallenberg, Kimberly A Dick, Jonas Johansson
III-V Nanowires (NWs) grown with metal-organic chemical vapor deposition commonly show a polytypic crystal structure, allowing growth of structures not found in the bulk counterpart. In this paper we studied the radial overgrowth of pure wurtzite (WZ) GaAs nanowires and characterized the samples with high resolution X-ray diffraction (XRD) to reveal the crystal structure of the grown material. In particular, we investigated what happens when adjacent WZ NWs radially merge with each other by analyzing the evolution of XRD peaks for different amounts of radial overgrowth and merging...
October 7, 2015: Crystal Growth & Design
Jian Lü, Li-Wei Han, Nada H Alsmail, Alexander J Blake, William Lewis, Rong Cao, Martin Schröder
The crystallization of two dihydropyridyl molecules, 1,4-bis(4-(3,5-dicyano-2,6-dipyridyl)dihydropyridyl)benzene ([C40H24N10]·2DMF, 1·2DMF; DMF = dimethylformamide) and 1,4-bis(4-(3,5-dicyano-2,6-dipyridyl)dihydropyridyl)phenylbenzene ([C46H28N10]·2DMF, 3·2DMF), and their respective oxidized pyridyl analogues, 1,4-bis(4-(3,5-dicyano-2,6-dipyridyl)pyridyl)benzene ([C40H20N10], 2) and 1,4-bis(4-(3,5-dicyano-2,6-dipyridyl)pyridyl)phenylbenzene ([C46H24N10]·DMF, 4·DMF), has been achieved under solvothermal conditions...
September 2, 2015: Crystal Growth & Design
Daniela Reischl, Christian Röthel, Paul Christian, Eva Roblegg, Heike M A Ehmann, Ingo Salzmann, Oliver Werzer
Polymorphism and morphology can represent key factors tremendously limiting the bioavailability of active pharmaceutical ingredients (API), in particular, due to solubility issues. Within this work, the generation of a yet unknown surface-induced polymorph (SIP) of the model drug, 5,5-diphenylimidazolidin-2,4-dion (phenytoin), is demonstrated in thin films through altering the crystallization kinetics and the solvent type. Atomic force microscopy points toward the presence of large single-crystalline domains of the SIP, which is in contrast to samples comprising solely the bulk phase, where extended dendritic phenytoin networks are observed...
September 2, 2015: Crystal Growth & Design
Christian Röthel, Michal Radziown, Roland Resel, Andreas Zimmer, Clemens Simbrunner, Oliver Werzer
Defined fabrication of organic thin films is highly desired in technological, as well as pharmaceutical, applications since morphology and crystal structure are directly linked to physical, electrical, and optical properties. Within this work, the directed growth of caffeine deposited by hot wall epitaxy (HWE) on muscovite mica is studied. Optical and atomic force microscopy measurements reveal the presence of caffeine needles exhibiting a preferable alignment in the azimuthal directions with respect to the orientation of the defined mica surface...
September 2, 2015: Crystal Growth & Design
Fei Wu, Debra D W Lin, Jin Ho Chang, Claudia Fischbach, Lara A Estroff, Delphine Gourdon
Hydroxyapatite (HAP, Ca10(PO4)6(OH)2) nanoparticles with controlled materials properties have been synthesized through a two-step hydrothermal aging method to investigate fibronectin (Fn) adsorption. Two distinct populations of HAP nanoparticles have been generated: HAP1 particles had smaller size, plate-like shape, lower crystallinity, and more negative ζ potential than HAP2 particles. We then developed two-dimensional platforms containing HAP and Fn and analyzed both the amount and the conformation of Fn via Förster resonance energy transfer (FRET) at various HAP concentrations...
May 6, 2015: Crystal Growth & Design
Adam D Martin, Joshua Britton, Timothy L Easun, Alexander J Blake, William Lewis, Martin Schröder
Six compounds based on dipicolinic acid esters have been synthesized and Hirshfeld surfaces used to investigate the structure-directing effects of functional groups in controlling their solid-state behavior. Compounds 1-4 are 4-bromo dipicolinic acid esters substituted with methyl, ethyl, propyl, and benzyl groups, respectively. The main structure-directing motif within 1-3 is a pairwise O···H interaction involving two carbonyl oxygen atoms and two aromatic H atoms. The introduction of bulky benzyl groups in 4 forces a significant change in the position of this interaction...
April 1, 2015: Crystal Growth & Design
Orion B Berryman, Charles A Johnson, Chris L Vonnegut, Kevin A Fajardo, Lev N Zakharov, Darren W Johnson, Michael M Haley
Utilizing an induced-fit model and taking advantage of rotatable acetylenic C(sp)-C(sp(2)) bonds, we disclose the synthesis and solid-state structures of a series of conformationally diverse bis-sulfonamide arylethynyl receptors using either pyridine, 2,2'-bipyridine, or thiophene as the core aryl group. Whereas the bipyridine and thiophene structures do not appear to bind guests in the solid state, the pyridine receptors form 2 + 2 dimers with water molecules, two halides, or one of each, depending on the protonation state of the pyridine nitrogen atom...
March 4, 2015: Crystal Growth & Design
Peter Neugebauer, Johannes G Khinast
Protein crystals have many important applications in many fields, including pharmaceutics. Being more stable than other formulations, and having a high degree of purity and bioavailability, they are especially promising in the area of drug delivery. In this contribution, the development of a continuously operated tubular crystallizer for the production of protein crystals has been described. Using the model enzyme lysozyme, we successfully generated product particles ranging between 15 and 40 μm in size. At the reactor inlet, a protein solution was mixed with a crystallization agent solution to create high supersaturations required for nucleation...
March 4, 2015: Crystal Growth & Design
Thibaut Devillers, Li Tian, Rajdeep Adhikari, Giulia Capuzzo, Alberta Bonanni
The structural analysis of GaN and Al x Ga1-x N/GaN heterostructures grown by metalorganic vapor phase epitaxy in the presence of Mn reveals how Mn affects the growth process and in particular, the incorporation of Al, the morphology of the surface, and the plastic relaxation of Al x Ga1-x N on GaN. Moreover, the doping with Mn promotes the formation of layered Al x Ga1-x N/GaN superlattice-like heterostructures, which opens wide perspectives for controlling the segregation of ternary alloys during the crystal growth and for fostering the self-assembling of functional layered structures...
February 4, 2015: Crystal Growth & Design
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