The Design of Organic Gelators Based on a Family of Bis-Ureas

1999 ◽  
Vol 604 ◽  
Author(s):  
Rosa E. Meléndez ◽  
Andrew J. Carn ◽  
Kazuki Sada ◽  
Andrew D. Hamilton
Keyword(s):  
Thermodynamic Properties ◽  
Organic Solvents ◽  
Organic Molecules ◽  
Materials Science ◽  
Crystallographic Data ◽  
Porous Solids ◽  
X Ray ◽  
Molecule Structure ◽  
Structure Activity ◽  
Potential Applications

AbstractThe use of organic molecules as gelators in certain organic solvents has been the target of recent research in materials science. The types of structures formed in the gel matrix have potential applications as porous solids that can be used as absorbents or in catalysis. We will present and discuss the organogelation properties of a family of bis-ureas. Studies presented will include a molecule structure activity relationship, thermodynamic properties, comparison to x-ray crystallographic data and potential functionalization of the gels formed by this class of compounds

High Resolution Replication of Organoclay Surfaces

1982 ◽  
Vol 40 ◽  
pp. 576-577
Author(s):  
W. W. Barker ◽  
W. E. Rigsby ◽  
V. J. Hurst ◽  
W. J. Humphreys
Keyword(s):  
Clay Mineral ◽  
Organic Molecule ◽  
Organic Molecules ◽  
X Ray Diffraction ◽  
Xrd Pattern ◽  
X Ray ◽  
Naturally Occurring ◽  
Silicate Layers ◽  
Mineral Identification

Experimental clay mineral-organic molecule complexes long have been known and some of them have been extensively studied by X-ray diffraction methods. The organic molecules are adsorbed onto the surfaces of the clay minerals, or intercalated between the silicate layers. Natural organo-clays also are widely recognized but generally have not been well characterized. Widely used techniques for clay mineral identification involve treatment of the sample with H2 O2 or other oxidant to destroy any associated organics. This generally simplifies and intensifies the XRD pattern of the clay residue, but helps little with the characterization of the original organoclay. Adequate techniques for the direct observation of synthetic and naturally occurring organoclays are yet to be developed.

Energy Dispersive X-Ray Measurements of thin Metal Foils

1976 ◽  
Vol 34 ◽  
pp. 426-427
Author(s):  
J. Bentley ◽  
E. A. Kenik
Keyword(s):  
Materials Science ◽  
Energy Dispersive Spectrometer ◽  
Thin Foil ◽  
Thin Metal ◽  
Energy Dispersive ◽  
Thin Specimen ◽  
X Ray ◽  
Metal Foils ◽  
Small Probe ◽  
Scanning Transmission

Instruments combining a 100 kV transmission electron microscope (TEM) with scanning transmission (STEM), secondary electron (SEM) and x-ray energy dispersive spectrometer (EDS) attachments to give analytical capabilities are becoming increasingly available and useful. Some typical applications in the field of materials science which make use of the small probe size and thin specimen geometry are the chemical analysis of small precipitates contained within a thin foil and the measurement of chemical concentration profiles near microstructural features such as grain boundaries, point defect clusters, dislocations, or precipitates. Quantitative x-ray analysis of bulk samples using EDS on a conventional SEM is reasonably well established, but much less work has been performed on thin metal foils using the higher accelerating voltages available in TEM based instruments.

X-ray microprobe for materials science

1994 ◽  
Vol 52 ◽  
pp. 56-57
Author(s):  
G.E. Ice
Keyword(s):  
Crystallographic Orientation ◽  
Local Structure ◽  
Materials Science ◽  
Chemical Information ◽  
X Ray Diffraction ◽  
Ray Optics ◽  
X Ray ◽  
Novel Materials ◽  
New Information ◽  
Elemental Sensitivity

The increasing availability of synchrotron x-ray sources has stimulated the development of advanced hard x-ray (E≥5 keV) microprobes. With new x-ray optics these microprobes can achieve micron and submicron spatial resolutions. The inherent elemental and crystallographic sensitivity of an x-ray microprobe and its inherently nondestructive and penetrating nature will have important applications to materials science. For example, x-ray fluorescent microanalysis of materials can reveal elemental distributions with greater sensitivity than alternative nondestructive probes. In materials, segregation and nonuniform distributions are the rule rather than the exception. Common interfaces to whichsegregation occurs are surfaces, grain and precipitate boundaries, dislocations, and surfaces formed by defects such as vacancy and interstitial configurations. In addition to chemical information, an x-ray diffraction microprobe can reveal the local structure of a material by detecting its phase, crystallographic orientation and strain.Demonstration experiments have already exploited the penetrating nature of an x-ray microprobe and its inherent elemental sensitivity to provide new information about elemental distributions in novel materials.

Electron holography of interfaces in electroceramics

1993 ◽  
Vol 51 ◽  
pp. 1088-1089
Author(s):  
Vinayak P. Dravid ◽  
V. Ravikumar ◽  
Richard Plass
Keyword(s):  
Space Charge ◽  
Direct Evidence ◽  
Materials Science ◽  
Theoretical Work ◽  
Electron Holography ◽  
Resolution Limit ◽  
Interference Phenomenon ◽  
X Ray ◽  
Electron Sources ◽  
Science Community

With the advent of coherent electron sources with cold field emission guns (cFEGs), it has become possible to utilize the coherent interference phenomenon and perform “practical” electron holography. Historically, holography was envisioned to extent the resolution limit by compensating coherent aberrations. Indeed such work has been done with reasonable success in a few laboratories around the world. However, it is the ability of electron holography to map electrical and magnetic fields which has caught considerable attention of materials science community.There has been considerable theoretical work on formation of space charge on surfaces and internal interfaces. In particular, formation and nature of space charge have important implications for the performance of numerous electroceramics which derive their useful properties from electrically active grain boundaries. Bonnell and coworkers, in their elegant STM experiments provided the direct evidence for GB space charge and its sign, while Chiang et al. used the indirect but powerful technique of x-ray microchemical profiling across GBs to infer the nature of space charge.

X-ray mapping without STEM

1994 ◽  
Vol 52 ◽  
pp. 508-509
Author(s):  
Judith M. Brock ◽  
Max T. Otten
Keyword(s):  
Life Science ◽  
Materials Science ◽  
Chemical Elements ◽  
Full Description ◽  
Scanning System ◽  
Elemental Distribution ◽  
X Ray ◽  
Transmission Electron ◽  
Distribution Of Elements ◽  
Made In

A knowledge of the distribution of chemical elements in a specimen is often highly useful. In materials science specimens features such as grain boundaries and precipitates generally force a certain order on mental distribution, so that a single profile away from the boundary or precipitate gives a full description of all relevant data. No such simplicity can be assumed in life science specimens, where elements can occur various combinations and in different concentrations in tissue. In the latter case a two-dimensional elemental-distribution image is required to describe the material adequately. X-ray mapping provides such of the distribution of elements.The big disadvantage of x-ray mapping hitherto has been one requirement: the transmission electron microscope must have the scanning function. In cases where the STEM functionality – to record scanning images using a variety of STEM detectors – is not used, but only x-ray mapping is intended, a significant investment must still be made in the scanning system: electronics that drive the beam, detectors for generating the scanning images, and monitors for displaying and recording the images.

Two Consecutive Magneto-Structural Gas-Solid Transformations with Single-Crystal Retention in Non-Porous Molecular Materials

2018 ◽  
Author(s):  
Julia Miguel-Donet ◽  
Javier López-Cabrelles ◽  
Nestor Calvo Galve ◽  
Eugenio Coronado ◽  
Guillermo Minguez Espallargas
Keyword(s):  
Solid State ◽  
Single Crystal ◽  
Structural Rearrangement ◽  
Magnetic Behaviour ◽  
Porous Solids ◽  
Potential Applications ◽  
Hcl Gas ◽  
Porous Coordination Polymer ◽  
Gas Molecules ◽  
Magnetostructural Transformation

<p>Modification of the magnetic properties in a solid-state material upon external stimulus has attracted much attention in the recent years for their potential applications as switches and sensors. Within the field of coordination polymers, gas sorption studies typically focus on porous solids, with the gas molecules accommodating in the channels. Here we present a 1D non-porous coordination polymer capable of incorporating HCl gas molecules, which not only causes a reordering of its atoms in the solid state but also provokes dramatic changes in the magnetic behaviour. Subsequently, a further solid-gas transformation can occur with the extrusion of HCl gas molecules causing a second structural rearrangement which is also accompanied by modification in the magnetic path between the metal centres. Unequivocal evidence of the two-step magnetostructural transformation is provided by X-ray single-crystal diffraction.</p>

Phenolic Imidazole Derivatives with Dual Antioxidant/Antifungal Activity: Synthesis and Structure-Activity Relationship

2019 ◽  
Vol 15 (4) ◽  
pp. 341-351 ◽  
Author(s):  
Ana P. Bettencourt ◽  
Marián Castro ◽  
João P. Silva ◽  
Francisco Fernandes ◽  
Olga P. Coutinho ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Antifungal Activity ◽  
Organic Molecules ◽  
Inhibitory Concentration ◽  
Yeast Species ◽  
Dpph Radical ◽  
Dpph Assay ◽  
Gram Negative ◽  
Structure Activity ◽  
Deoxyribose Degradation

Background: Previous publications show that the addition of a phenolic antioxidant to an antifungal agent, considerably enhances the antifungal activity. Objective: Synthesis of novel compounds combining phenolic units with linear or cyclic nitrogencontaining organic molecules with antioxidant/antifungal activity using methodologies previously developed in the group. Methods: Several N- [1,2-dicyano-2- (arylidenamino) vinyl]-O-alkylformamidoximes 3 were synthesized and cyclized to 4,5-dicyano-N- (N´-alcoxyformimidoyl)-2-arylimidazoles 4 upon reflux in DMF, in the presence of manganese dioxide or to 6-cyano-8-arylpurines 5 when the reagent was refluxed in acetonitrile with an excess of triethylamine. These compounds were tested for their antioxidant activity by cyclic voltammetry, DPPH radical (DPPH•) assay and deoxyribose degradation assay. The minimum inhibitory concentration (MIC) of all compounds was evaluated against two yeast species, Saccharomyces cerevisiae and Candida albicans, and against bacteria Bacillus subtilis (Gram-positive) and Escherichia coli (Gram negative). Their cytotoxicity was evaluated in fibroblasts. Results: Among the synthetised compounds, five presented higher antioxidant activity than reference antioxidant Trolox and from these compounds, four presented antifungal activity without toxic effects in fibroblasts and bacteria. Conclusion: Four novel compounds presented dual antioxidant/antifungal activity at concentrations that are not toxic to bacteria and fibroblasts. The active molecules can be used as an inspiration for further studies in this area.

scholarly journals Solvent-Controlled Self-Assembled Oligopyrrolic Receptor

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1771
Author(s):  
Fei Wang ◽  
Kejiang Liang ◽  
Mads Christian Larsen ◽  
Steffen Bähring ◽  
Masatoshi Ishida ◽  
...  
Keyword(s):  
Materials Science ◽  
Science Research ◽  
Polymeric Chain ◽  
Supramolecular System ◽  
Receptor System ◽  
One Dimensional ◽  
X Ray ◽  
Host Guest Complex ◽  
Colorimetric Response ◽  
Strong Acids

We report a fully organic pyridine-tetrapyrrolic U-shaped acyclic receptor 10, which prefers a supramolecular pseudo-macrocyclic dimeric structure (10)2 in a less polar, non-coordinating solvent (e.g., CHCl3). Conversely, when it is crystalized from a polar, coordinating solvent (e.g., N,N-dimethylformamide, DMF), it exhibited an infinite supramolecular one-dimensional (1D) “zig-zag” polymeric chain, as inferred from the single-crystal X-ray structures. This supramolecular system acts as a potential receptor for strong acids, e.g., p-toluenesulfonic acid (PTSA), methane sulfonic acid (MSA), H2SO4, HNO3, and HCl, with a prominent colorimetric response from pale yellow to deep red. The receptor can easily be recovered from the organic solution of the host–guest complex by simple aqueous washing. It was observed that relatively stronger acids with pKa < −1.92 in water were able to interact with the receptor, as inferred from 1H NMR titration in tetrahydrofuran-d8 (THF-d8) and ultraviolet–visible (UV–vis) spectroscopic titrations in anhydrous THF at 298 K. Therefore, this new dynamic supramolecular receptor system may have potentiality in materials science research.

Theoretically derived thermodynamic properties can be improved by the refinement of low-frequency modes against X-ray diffraction data

2021 ◽  
Author(s):  
Anna Agnieszka Hoser ◽  
Marcin Sztylko ◽  
Damian Trzybiński ◽  
Anders Østergaard Madsen
Keyword(s):  
Thermodynamic Properties ◽  
Dft Calculations ◽  
Diffraction Data ◽  
Molecular Crystals ◽  
Low Frequency ◽  
X Ray Diffraction ◽  
X Ray ◽  
Efficient Approach

A framework for estimation of thermodynamic properties for molecular crystals via refinement of frequencies from DFT calculations against X-ray diffraction data is presented. The framework provides an efficient approach to...

scholarly journals A pH-Responsive Foam Formulated with PAA/Gemini 12-2-12 Complexes

2021 ◽  
Vol 5 (3) ◽  
pp. 37
Author(s):  
Hernán Martinelli ◽  
Claudia Domínguez ◽  
Marcos Fernández Leyes ◽  
Sergio Moya ◽  
Hernán Ritacco
Keyword(s):  
Surface Tension ◽  
Dynamic Surface Tension ◽  
Foam Formation ◽  
Ph Responsive ◽  
Dynamic Surface ◽  
X Ray ◽  
Equilibrium Surface Tension ◽  
Potential Applications ◽  
The Stability ◽  
Air Interfaces

In the search for responsive complexes with potential applications in the formulation of smart dispersed systems such as foams, we hypothesized that a pH-responsive system could be formulated with polyacrylic acid (PAA) mixed with a cationic surfactant, Gemini 12-2-12 (G12). We studied PAA-G12 complexes at liquid–air interfaces by equilibrium and dynamic surface tension, surface rheology, and X-ray reflectometry (XRR). We found that complexes adsorb at the interfaces synergistically, lowering the equilibrium surface tension at surfactant concentrations well below the critical micelle concentration (cmc) of the surfactant. We studied the stability of foams formulated with the complexes as a function of pH. The foams respond reversibly to pH changes: at pH 3.5, they are very stable; at pH > 6, the complexes do not form foams at all. The data presented here demonstrate that foam formation and its pH responsiveness are due to interfacial dynamics.

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