The Crystal Solvate Phase of Heteroaromatic Rigid Polymers Yachin Cohen

1988 ◽  
Vol 134 ◽  
Keyword(s):  
Electron Microscopy ◽  
Polyphosphoric Acid ◽  
Three Dimensional ◽  
Polymer Chains ◽  
Crystal Solvate ◽  
X Ray Diffraction ◽  
Ordered Structures ◽  
Crystal Solvates ◽  
X Ray ◽  
Rigid Polymers

ABSTRACTThis work concerns solutions of the rigid polymers: poly(p-phenylene benzobisthiazole)-PBZT, and poly(p-phenylene benzobisoxazole)-PBO, in polyphosphoric acid (PPA), and formation of a crystal solvate phase by cocrystallization of polymer and solvent. Several crystal-solvate phases have been observed in these solutions, depending on temperature and the extent of exposure to moisture. The structure of these phases is studied by X-ray diffraction. Transitions between the solvated phases involve changes in the lateral packing as well as the axial registry of parallel chains. All PBOPPA crystal solvates observed so far exhibit three-dimensional order, whereas such order appears only in the PBZT-PPA phase obtained at low moisture levels. These differences are interpreted in terms of the state of protonation of the polymer chains, whereby the highly ordered structures reflect unique associations of the protonated polycation and PPA anions. Observations by electron microscopy indicate that the transition from the highly ordered crystal solvate phase to the less ordered phase involves formation of thin microfibrils, less than 100 Å in width. These microfibrils may be the precursor of the microfibrillar morphology observed in fibers formed from solutions of the rigid polymers.

scholarly journals Synthesis of Three-Dimensional Fe3O4/Graphene Aerogels for the Removal of Arsenic Ions from Water

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Yan Ye ◽  
Da Yin ◽  
Bin Wang ◽  
Qingwen Zhang
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
3D Structure ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Graphene Aerogels ◽  
Transmission Electron ◽  
Potential Applications ◽  
Removal Of Arsenic

We report the synthesis of three-dimensional Fe3O4/graphene aerogels (GAs) and their application for the removal of arsenic (As) ions from water. The morphology and properties of Fe3O4/GAs have been characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and superconducting quantum inference device. The 3D nanostructure shows that iron oxide nanoparticles are decorated on graphene with an interconnected network structure. It is found that Fe3O4/GAs own a capacity of As(V) ions adsorption up to 40.048 mg/g due to their remarkable 3D structure and existence of magnetic Fe3O4nanoparticles for separation. The adsorption isotherm matches well with the Langmuir model and kinetic analysis suggests that the adsorption process is pseudo-second-ordered. In addition to the excellent adsorption capability, Fe3O4/GAs can be easily and effectively separated from water, indicating potential applications in water treatment.

Bioinspired synthesis of self-assembled calcium phosphate nanocomposites using block copolymer-peptide conjugates

2008 ◽  
Vol 23 (12) ◽  
pp. 3196-3212 ◽  
Author(s):  
Yusuf Yusufoglu ◽  
Yanyan Hu ◽  
Mathumai Kanapathipillai ◽  
Matthew Kramer ◽  
Yunus E. Kalay ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Calcium Phosphate ◽  
Small Angle ◽  
Polymer Chains ◽  
X Ray Diffraction ◽  
X Ray ◽  
Self Assembling ◽  
Transmission Electron ◽  
Angle Scattering ◽  
Inorganic Content

Thermoreversibly gelling block copolymers conjugated to hydroxyapatite-nucleating peptides were used to template the growth of inorganic calcium phosphate in aqueous solutions. Nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), transmission electron microscopy, x-ray diffraction, and small-angle scattering were used to characterize these samples and confirm that the peptides promoted the growth of hydroxyapatite as the inorganic phase. Three different polymer templates were used with varying charges on the polymer chains (nonionic, anionic, and zwitterionic), to investigate the role of charge on mineralization. All of the polymer-inorganic solutions exhibited thermoreversible gelation above room temperature. Nanocomposite formation was confirmed by solid-state NMR, and several methods identified the inorganic component as hydroxyapatite. Small angle x-ray scattering and electron microscopy showed thin, elongated crystallites. Thermogravimetric analysis showed an inorganic content of 30–45 wt% (based on the mass of the dried gel at ∼200 °C) in the various samples. Our work offers routes for bioinspired bottom-up approaches for the development of novel, self-assembling, injectable nanocomposite biomaterials for potential orthopedic applications.

scholarly journals Synthesis of NiW Supported on an Al-Modified Cubic Ia3d Mesoporous KIT-5 Catalyst and Its Hydrodenitrogenation Performance of Quinoline

Catalysts ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1183
Author(s):  
Xing Liu ◽  
Shaoqing Guo ◽  
Xin Li ◽  
Lijing Yuan ◽  
Hongyu Dong ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Fourier Transform ◽  
Three Dimensional ◽  
Fourier Transform Infrared ◽  
Photoelectron Spectra ◽  
Sulfide Catalysts ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Large Pore Size

Pure KIT-5 and a series of Al-KT-X materials modified by different amounts of aluminum were synthesized by a direct hydrothermal method and acted as supports for the catalysts of a quinoline hydrodenitrification reaction with the NiW active phases supported. The results of X-ray diffraction (XRD), N2 isotherm absorption-desorption, scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) for the supports indicated that Al species were embedded into the framework of the KIT-5 materials with a large pore size, pore volume, and specific surface area. The Pyridine-Fourier transform infrared spectroscopy (Py-IR) result of the catalysts demonstrated that the addition of aluminum atoms enhanced the acidity of the catalysts. The results of the high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectra (XPS) characterizations for the sulfide catalysts indicated that the embedded Al species could facilitate the dispersion of active metals and the formation of the active phases. Among all the catalysts, NiW/Al-KT-40 showed the maximal hydrodenitrogenation conversion (HDNC) due to its open three-dimensional pore structure, appropriate acidity, and good dispersion of active metals.

Three-Dimensional Coherent X-Ray Diffraction Microscopy

MRS Bulletin ◽  
2004 ◽  
Vol 29 (3) ◽  
pp. 177-181 ◽  
Author(s):  
Ian K. Robinson ◽  
Jianwei Miao
Keyword(s):  
Electron Microscopy ◽  
Three Dimensional ◽  
Real Space ◽  
Objective Lens ◽  
X Rays ◽  
X Ray Diffraction ◽  
Space Images ◽  
Thin Sections ◽  
X Ray ◽  
Penetration Ability

AbstractX-rays have been widely used in the structural analysis of materials because of their significant penetration ability, at least on the length scale of the granularity of most materials. This allows, in principle, for fully three-dimensional characterization of the bulk properties of a material. One of the main advantages of x-ray diffraction over electron microscopy is that destructive sample preparation to create thin sections is often avoidable. A major disadvantage of x-ray diffraction with respect to electron microscopy is its inability to produce real-space images of the materials under investigation—there are simply no suitable lenses available. There has been significant progress in x-ray microscopy associated with the development of lenses, usually based on zone plates, Kirkpatrick–Baez mirrors, or compound refractive lenses. These technologies are far behind the development of electron optics, particularly for the large magnification ratios needed to attain high resolution. In this article, the authors report progress toward the development of an alternative general approach to imaging, the direct inversion of diffraction patterns by computation methods. By avoiding the use of an objective lens altogether, the technique is free from aberrations that limit the resolution, and it can be highly efficient with respect to radiation damage of the samples. It can take full advantage of the three-dimensional capability that comes from the x-ray penetration. The inversion step employs computational methods based on oversampling to obtain a general solution of the diffraction phase problem.

Green synthesis of dual-surface nanocomposite films using Tollen’s method

2014 ◽  
Vol 3 (6) ◽  
Author(s):  
Sayed M. Badawy
Keyword(s):  
Electron Microscopy ◽  
Ag Nanoparticles ◽  
Color Change ◽  
Polymer Chains ◽  
Nanocomposite Films ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structure And Morphology ◽  
Pva Solutions ◽  
Scanning Electron

AbstractNanocomposite films with dual-surface, silver (Ag) layers and silver-polyvinyl alcohol (Ag-PVA) bulk layers were prepared by Tollen’s reagent using β-D-glucose as a green reducing agent in water as an environmentally-friendly solvent and in PVA as a bio-friendly polymer. The gradual color change of Ag in PVA solutions from colorless to light brown and then to brown, and finally dark brown, indicated the formation of Ag nanoparticles in the bulk of the PVA solution which finally formed Ag layers on the inner side of the glass. Energy dispersive X-ray (EDX) analysis and X-ray diffraction (XRD) were used to characterize the nanocomposite films with two surfaces. The Ag content of the Ag layers reached 93% with a higher crystallinity. The Ag content of the Ag-PVA bulk layers reached 10.8% with a lower crystallinity due to incorporation of Ag nanoparticles in the polymer chains. The structure and morphology of the two surfaces were confirmed by scanning electron microscopy (SEM).

Microcavity Effects in The Luminescence of GaAs Microcrystals

1992 ◽  
Vol 283 ◽  
Author(s):  
S. Juen ◽  
K. F. Lamprecht ◽  
R. Rodrigues ◽  
R. A. Höpfel
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
Three Dimensional ◽  
Photoluminescence Spectra ◽  
X Ray Diffraction ◽  
Bulk Gaas ◽  
X Ray ◽  
Transmission Electron ◽  
Spectral Enhancement

ABSTRACTExperimental photoluminescence spectra of GaAs microcrystals show pronounced variations compared to the luminescence of bulk GaAs. The observed spectra are explained by spectral enhancement and inhibition of spontaneous emission in a three-dimensional optical resonator formed by a dielectrically confined semiconductor microcrystal. The crystals were produced by pulverization of bulk GaAs, size-separated by sedimentation techniques, and characterized by transmission electron microscopy, electron diffraction and x-ray diffraction.

Synthesis Of Highly Ordered Macroporous Minerals: Extension of the Synthetic Method to Other Metal Oxides and Organic-Inorganic Composites

1998 ◽  
Vol 549 ◽  
Author(s):  
C.F. Blanford ◽  
T.N. Do ◽  
B.T. Holland ◽  
A. Stein
Keyword(s):  
Electron Microscopy ◽  
Metal Oxides ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Wide Range ◽  
Ordered Macroporous ◽  
Lower Temperature

AbstractThe facile synthesis of three-dimensional macroporous arrays of titania, zirconia and alumina was recently reported [1]. The synthesis of these materials has now been extended to the oxides of iron, tungsten, and antimony, as well as a mixed yttrium-zirconium system and organically modi- fied silicates. These materials were characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray energy dispersive spectrometry (EDS), and powder X-ray diffraction (XRD). Ordered structures of iron, tungsten, and antimony were formed from alkoxide precursors as in the originally reported synthesis, but the template was removed at a lower temperature. Samples of vinyl- and 2-cyanoethyl-modified silicates were formed from a mixture of organotrialkoxysilane and tetraalkoxysilane precursors; the polystyrene template was removed by extraction with a THF/acetone mixture. These results show the ease of extending the original syn- thesis to a wide range of systems. Also, the ability to form homogenous mixed-metal oxides will be important for tailoring the dielectric and photonic properties of these materials.

scholarly journals Synthesis, crystal structure, and thermal properties of poly[aqua(μ5-2,5-dicarboxybenzene-1,4-dicarboxylato)strontium]

2020 ◽  
Vol 76 (3) ◽  
pp. 354-359
Author(s):  
Samia Mokhtari ◽  
Chahrazed Trifa ◽  
Sofiane Bouacida ◽  
Chaouki Boudaren ◽  
Mohammed S.M. Abdelbaky ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Thermal Analysis ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Tetracarboxylic Acid ◽  
X Ray Diffraction ◽  
X Ray ◽  
Carboxylate Groups ◽  
Scanning Electron

A coordination polymer formulated as [Sr(H2BTEC)(H2O)] n (H4BTEC = benzene-1,2,4,5-tetracarboxylic acid, C10H6O8), was synthesized hydrothermally and characterized by single-crystal and powder X-ray diffraction, scanning electron microscopy and thermal analysis. Its crystal structure is made up of a zigzag inorganic chain formed by edge-sharing of [SrO8] polyhedra running along [001]. Adjacent chains are connected to each other via the carboxylate groups of the ligand, resulting in a double-layered network extending parallel to (100). O—H...O hydrogen bonds of medium-to-weak strength between the layers consolidate the three-dimensional structure. One of the carboxylic OH functions was found to be disordered over two sets of sites with half-occupancy.

Organized packing of RNA inside viruses as revealed by cryo-electron microscopy and x-ray diffraction analysis

1992 ◽  
Vol 50 (1) ◽  
pp. 454-455
Author(s):  
T. S. Baker ◽  
R. H. Cheng ◽  
J. E. Johnson ◽  
N. H. Olson ◽  
G. J. Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Diffraction Analysis ◽  
Three Dimensional ◽  
Biological Macromolecules ◽  
Three Dimensional Reconstruction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cryo Electron Microscopy ◽  
Dimensional Reconstruction ◽  
Microscopy Techniques

The development of modern electron microscopy techniques to visualize the hydrated structures of biological macromolecules has stimulated many new studies, especially with viruses and virus-macromolecule complexes that are too large to study with current x-ray crystallographic methods, Cryo-electron microscopy (cryoEM) in conjunction with three-dimensional reconstruction procedures is capable of revealing both external and internal features of these structures.

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