Search results for "Crystallization"
showing 10 items of 774 documents
O-Doped Nanographenes: A Pyrano/Pyrylium Route Towards Semiconducting Cationic Mixed-Valence Complexes
2020
Herein we report an efficient synthesis to prepare O‐doped nanographenes, which derive from the longitudinally and latitudinally p‐extension of pyrene. The derivatives are highly fluorescent and feature low‐oxidation potentials. Exploiting electrooxidation, crystals of cationic mixed valence (MV) complexes were grown in which the organic salts organize into face‐to‐face p‐ p stacks, a favorable solid‐state arrangement for organic electronics. Variable‐temperature EPR measurements and relaxation studies suggest a strong electron delocalization along the longitudinal axis of the columnar p‐stacking architectures. Electric measurements of single crystals of the MV salts exhibited a semiconduct…
Exploring Zinc Apatites through Different Synthesis Routes
2013
nclusion of zinc in apatites is not completely understood due to complexes in solution preventing the incorporation or the inclusion of defects. Some work has shown zinc addition by alternative synthesis routes, but the level of incorporation has not been reassessed. This work uses a newly developed approach whereby zinc is included in an amorphous phase and subsequently crystallized. Different phosphate reactants (ammonium, sodium or potassium phosphates) were mixed together with calcium salts (calcium nitrate or calcium acetate) and the pH level adjusted (with ammonia or KOH) to investigate the ease of forming an amorphous phase and the inclusion of zinc. X-ray diffraction revealed that a…
Diaqua[5,10,15,20-tetrakis(4-chlorophenyl)porphyrinato-κ4N]iron(III) trifluoromethanesulfonate–4-hydroxy-3-methoxybenzaldehyde–water (1/1/2)
2014
In the title compound, [Fe(C44H24Cl4N4)(H2O)2](SO3CF3)·C8H8O3·2H2O, the FeIIIcation is chelated by the four N atoms of the deprotonated tetrakis(4-chlorotetraphenyl)porphyrin (TClPP) and further coordinated by two water molecules in a distorted octahedral geometry. In the crystal, the cations, anions, 4-hydroxy-3-methoxybenzaldehyde and water molecules of crystallization are linked by classical O—H...O hydrogen bonds and weak C—H...O and C—H...Cl hydrogen bonds into a three-dimensional supramolecular architecture. The crystal packing is further stabilized by weak C—H...π interactions involving pyrrole and benzene rings. π–π stacking between parallel benzene rings of adjacent 4-hydroxy-3-met…
High Temperature Study of Metamict Steenstrupine
2010
Metamict minerals contain radioactive elements that degrade their crystal structure. Unlike other metamict minerals, annealing process under ambient pressure do not lead to direct recrystallization of steenstrupine.
Alignment-free, all-spliced fiber laser source for CARS microscopy based on four-wave-mixing
2012
An environmentally-stable low-repetition rate fiber oscillator is developed to produce narrow-bandwidth pulses with several tens of picoseconds duration. Based on this oscillator an alignment-free all-fiber laser for multi-photon microscopy is realized using in-fiber frequency conversion based on four-wave-mixing. Both pump and Stokes pulses for coherent anti-Stokes Raman scattering (CARS) microscopy are readily available from one fiber end, intrinsically overlapped in space and time, which drastically simplifies the experimental handling for the user. The complete laser setup is mounted on a home-built laser scanning microscope with small footprint. High-quality multimodal microscope image…
Retrograde melt-residue interaction and the formation of near-anhydrous leucosomes in migmatites
2010
Considering physical segregation of melt from its residue, the chemical potentials of the components (oxides) are the same in both when segregation occurs. Then, as P–T conditions change, gradients in chemical potential are established between the melt-rich domains and residue permitting diffusional interaction to occur. In particular, on cooling, the chemical potential of H2O becomes higher in the melt segregation than in the residue, particularly when biotite becomes stable in the residue assemblage. Diffusion of water from the melt to the residue promotes crystallization of anhydrous products from the melt and hydrous products in the residue. This diffusive process, when coupled with mel…
Nonclassical crystallization in vivo et in vitro (I): Process-structure-property relationships of nanogranular biominerals.
2016
A distinct nanogranular fine structure is shared by a wealth of biominerals from several species, classes and taxa. This nanoscopic organization affects the properties and behavior of the biogenic ceramic material and confers on them attributes that are essential to their function. We present a set of structure-relationship properties that are rooted in the nanogranular organization and we propose that they rest on a common pathway of formation, a colloid-driven and hence nonclassical mode of crystallization. With this common modus operandi, we reveal the most fundamental and wide spread process-structure-property relationship in biominerals. With the recent increase in our understanding of…
Estimation of the mean crystal size and the moments of the crystal size distribution in batch crystallization processes
2016
International audience; A cascade high gain observer is designed to estimate the first four leading moments of the crystal size distribution (CSD) and the mean crystal size in batch crystallization processes. The proposed observer is based on a well-known transformation of the partial differential equation describing the CSD to a set of ordinary differential equations (the method of moments). Due to numerical difficulties resulting from the important differences in the magnitudes of the moments, a set of new variables is computed to allow a good estimation of the moments and thus the mean crystal size. In this work, only solute concentration and crystallizer temperature are used to estimate…
Targeting Cavity-Creating p53 Cancer Mutations with Small-Molecule Stabilizers: the Y220X Paradigm
2020
We have previously shown that the thermolabile, cavity-creating p53 cancer mutant Y220C can be reactivated by small-molecule stabilizers. In our ongoing efforts to unearth druggable variants of the p53 mutome, we have now analyzed the effects of other cancer-associated mutations at codon 220 on the structure, stability, and dynamics of the p53 DNA-binding domain (DBD). We found that the oncogenic Y220H, Y220N, and Y220S mutations are also highly destabilizing, suggesting that they are largely unfolded under physiological conditions. A high-resolution crystal structure of the Y220S mutant DBD revealed a mutation-induced surface crevice similar to that of Y220C, whereas the corresponding pock…
Cyclic triureas—synthesis, crystal structures and properties
2008
The synthesis of 24-membered macrocycles is described, in which rigid xanthene units (X) and/or diphenyl ether units (D) as flexible analogues are linked via urea groups. All four possible combinations (XXX, XXD, XDD, DDD) have been obtained with yields of 40-72% for the cyclisation step. In two cases, the respective cyclic hexamers (XXDXXD, XXXXXX) were also isolated. Two compounds have been characterised by a single crystal X-ray analysis of the free triurea (XXD, XDD) and one example (DDD) by its complex with tetrabutylammonium chloride. It shows the chloride anion in the centre of the macrocycle, held by six NH...Cl- hydrogen bonds. The interaction with various other anions has been stu…