1,721,145 research outputs found
Insights into the self-assembly of fampridine hydrochloride:how the choice of the solvent affects the crystallization of a simple salt
Full text linkCrystalline materials and crystallization processes play an important role in several fields of science, such as pharmaceuticals, material science, pigments, optoelectronics, catalysis and energy storage. Under- standing and defining the right conditions of crystallization is therefore crucial. Among the several factors influencing the crystallization of a given compound, the choice of the solvent system is perhaps one of the most important. The nature of solvent–solute interactions can indeed have a role in promoting specific molecular assemblies, therefore affecting crystallisation rates of a crystal and often resulting in the nucleation of different polymorphs and solvates. Here we investigated the role of a binary mixture of solvent (water/acetone) in the crystallisation of a simple salt of 4-aminopyridinium chloride. Previous results on this compound showed that when crystallised from water it forms a simple hydrate structure, while in the presence of acetone, it undergoes a liquid-liquid phase separation, followed by the crystallisation of a complex structure belonging to the Frank–Kasper (FK) phases, a particular family of topologically close-packed structures never observed in small and rigid molecules. To broaden the understanding of how such a simple molecule may crystallise as an FK phase, we carried out the crystallization of the complex phase by antisolvent diffusion (in a mixture of water/acetone) and that of the monohydrate phase in water, monitoring the liquid precursors by liquid-state NMR. In particular, we applied 1H, 13C, 14N, 17O, and 35/37Cl NMR as a function of the concentration of 4APH+Cl− until the moment when precipitation of the crystalline phases occurred. Variations of chemical shifts, T1 relaxation times of 13C signals, and full-width at half-maximum of the signals of quadrupolar nuclei were also measured. The spatial proximity between the different species in the solution was investigated by NOE experiments. In order to support these results, we also performed Molecular Dynamics simulations, investigating the potential solute/solvents in- teractions. The results strongly suggest that acetone, instead of behaving as an anti-solvent, interacts directly with the solute, preventing the formation of the simple monohydrate structure and, at the same time, promoting specific molecular aggregations
Design and Catalytic Applications of 1D tubular nanostructures:Improving Efficiency in Glycerol Conversion
No full textThe design of novel and efficient heterogeneous catalysts represents one of the main challenges in the development of sustainable processes. A straightforward one-pot sol-gel approach for the controlled preparation of highly active 1D nanotubes is herein presented. The optimization of the synthesis parameters allowed obtaining materials with tubular structure and very high surface area even in the absence of additional hydrothermal treatments hence further reducing the environmental impact of the synthesis approach. The isomorphic substitution of Sn within the silica framework was assessed via 119Sn solid state NMR under static conditions. Sn-silica nanotubes were efficiently used to catalyze both the transformation of dihydroxyacetone into ethyl lactate and the conversion of glycerol into solketal, where outstanding turnover frequencies were obtained under solvent-free conditions. The catalytic performance of these materials is ascribed to the enhanced accessibility of their active sites given by their tubular morphology and to the suitable combination of acid sites. Moreover, no-leaching of active sites was evidenced and the best solid preserved its activity in multiple catalytic cycles. Characterization after the reuses allows supporting further the stability of tin-nanotubes under the selected reactions conditions
Effect and differentiation activity of IGF-I, IGF-II, insulin and preptin on human primary bone cells.
No full textGrafted-modified PLLA: new approaches for phenotype guiding in cardiovascular tissue engineering
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Politetrafluorene suture used as artificial mitral chord: Mechanical properties and surgical implications
No full textCellular distribution geno and cytotoxic effects of modified PEI nanoparticles to be used as siRNA in tissue engineering applications
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