scholarly journals Robust Ruthenium Catalysts Supported on Mesoporous Cyclodextrin-Templated TiO2-SiO2 Mixed Oxides for the Hydrogenation of Levulinic Acid to γ-Valerolactone

2021 ◽  
Vol 22 (4) ◽  
pp. 1721
Author(s):  
Cédric Decarpigny ◽  
Sébastien Noël ◽  
Ahmed Addad ◽  
Anne Ponchel ◽  
Eric Monflier ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Aqueous Phase ◽  
Levulinic Acid ◽  
Mixed Oxides ◽  
Building Blocks ◽  
Strong Impact ◽  
Pore Characteristics ◽  
Assembly Method ◽  
Transmission Electron

In this paper, we present a versatile template-directed colloidal self-assembly method for the fabrication in aqueous phase of composition-tuned mesoporous RuO2@TiO2-SiO2 catalysts. Randomly methylated β-cyclodextrin/Pluronic F127 supramolecular assemblies were used as soft templates, TiO2 colloids as building blocks, and tetraethyl orthosilicate as a silica source. Catalysts were characterized at different stages of their synthesis using dynamic light scattering, N2-adsorption analysis, powder X-ray diffraction, temperature programmed reduction, high-resolution transmission electron microscopy, high-angle annular bright-field and dark-field scanning transmission electron microscopy, together with EDS elemental mapping. Results revealed that both the supramolecular template and the silica loading had a strong impact on the pore characteristics and crystalline structure of the mixed oxides, as well as on the morphology of the RuO2 nanocrystals. Their catalytic performance was then evaluated in the aqueous phase hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) under mild conditions (50 °C, 50 bar H2). Results showed that the cyclodextrin-derived catalyst displayed almost quantitative LA conversion and 99% GVL yield in less than one hour. Moreover, this catalyst could be reused at least five times without loss of activity. This work offers an effective approach to the utilization of cyclodextrins for engineering the surface morphology of Ru nanocrystals and pore characteristics of TiO2-based materials for catalytic applications in hydrogenation reactions.

Transmission electron microscopy on metal–organic frameworks – a review

2017 ◽  
Vol 5 (29) ◽  
pp. 14969-14989 ◽  
Author(s):  
Christian Wiktor ◽  
Maria Meledina ◽  
Stuart Turner ◽  
Oleg I. Lebedev ◽  
Roland A. Fischer
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Spatial Distribution ◽  
Chemical Reactions ◽  
Metal Organic Frameworks ◽  
Building Blocks ◽  
Transmission Electron ◽  
Metal Organic ◽  
Surface Facets

Versatile materials like MOFs require careful characterization. TEM can be used to determine and identify the crystal structure and surface facets of MOFs, the spatial distribution of guests or building blocks in them and how they are changed in chemical reactions.

Sonochemical synthesis of large-scale single-crystal PbS nanorods

2003 ◽  
Vol 18 (5) ◽  
pp. 1188-1191 ◽  
Author(s):  
S. M. Zhou ◽  
Y. S. Feng ◽  
L. D. Zhang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Single Crystal ◽  
Large Scale ◽  
Three Dimensional ◽  
Ultrasound Irradiation ◽  
Building Blocks ◽  
Uniform Structure ◽  
X Ray ◽  
Transmission Electron

Large-scale single-crystal cubic PbS nanorods were successfully achieved by using ultrasound irradiation in certain ethylenediamine tetraacetic acid (EDTA) solutions, particularly in the solution of Pb:EDTA = 1:1. The obtained PbS nanorods were characterized using x-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersed x-ray spectrometry, selected area electronic diffraction, and high-resolution transmission electron microscopy. The results reveal that the PbS nanorods with straight and uniform structure have a diameter of about 70–80 nm and length of about 1000 nm, where the growth mechanism is tentatively discussed. The successful synthesis of these cubic structure semiconductor PbS nanorods may open up new possibilities for using these materials as building blocks to create functional two-dimensional or three-dimensional nanostructured materials.

scholarly journals Heterostructural Mixed Oxides Prepared via ZnAlLa LDH or ex-ZnAl LDH Precursors—Effect of La Content and Its Incorporation Route

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2082
Author(s):  
Katarzyna Antoniak-Jurak ◽  
Paweł Kowalik ◽  
Wiesław Próchniak ◽  
Robert Bicki ◽  
Grzegorz Słowik
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Thermal Treatment ◽  
Mixed Oxides ◽  
X Ray ◽  
Transmission Electron ◽  
Co Precipitation ◽  
Znal2o4 Spinel

The effect of La content and its incorporation route on physicochemical properties of ZnO/Zn(Al,La)2O4 or La2O3–ZnO/ZnAl2O4 mixed oxides with a spinel structure obtained from ZnAlLa Layered double hydroxides (LDHs) or ex-ZnAl LDH materials was investigated. The heterostructural nanocomposites with the similar Zn/Al molar ratio and varied La content were prepared by two techniques: via co-precipitation and thermal treatment of ZnAlLa LDHs at 500 °C or via incipient wetness impregnation of ex-ZnAl LDHs with aqueous solutions of lanthanum nitrate and subsequent thermal treatment. The obtained series of materials were characterized by the following techniques: X-ray fluorescence (XRF), N2 adsorption (BET), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis with evolved gas analysis (TG/DTG/EGA), scanning transmission electron microscopy (STEM) energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM) and Fourier-transform infrared spectroscopy (FFT). The evaluation of activity toward the high-temperature water gas shift (HT-WGS) within the temperature range of 350–420 °C was carried out on the basis of rate constant measurements in the kinetic mode using a differential reactor. The co-precipitation technique allowed for a better distribution of La in bulk and on the spinel surface than in case of lanthanum incorporation via impregnation. ZnO/Zn(Al,La)2O4 or La2O3–ZnO/ZnAl2O4 mixed oxides were characterized by moderate activity in the HT-WGS reaction. The results reveal that introduction of lanthanum oxide over 2.4–2.8 wt% induces the phase separation of the ZnAl2O4 spinel, forming ZnO on the ZnAl2O4 spinel surface.

Protonation state of core nitrogens in the meso-tetra(4-carboxyphenyl)porphyrin impacts the chemical and physical properties of nanostructures formed in acid solutions

2012 ◽  
Vol 16 (12) ◽  
pp. 1233-1243 ◽  
Author(s):  
Jeremy R. Eskelsen ◽  
Yingte Wang ◽  
Yun Qui ◽  
Monali Ray ◽  
Mzuri Handlin ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Elevated Temperatures ◽  
Building Blocks ◽  
Acid Solutions ◽  
Protonation State ◽  
Preparation Temperature ◽  
Transmission Electron ◽  
Self Assembled

Organic self-assemblies of meso-tetra (4-carboxyphenyl)porphine (TCPP) prepared in trifluoroacetic acid (TFA) and hydrochloric acid solutions at pH < 1 were studied by X-ray photoelectron spectroscopy (XPS) in order to determine the protonation state of the porphyrin building blocks present in the solid self-assembled nanostructures. XPS measurements were conducted both at room and at elevated temperatures. Room temperature N 1s spectra showed two bands with a 3:1 intensity ratio consistent with three protonated and one unprotonated nitrogen in the structures prepared in both TFA and HCl solutions. We attribute this result to TCPP existing as a 50:50 mixture of the free-base and diacid forms of the porphyrin core in the self-assembled state. Upon heating to 150 °C the TCPP/TFA and TCPP/HCl nanomaterials exhibit loss of pyrrolic hydrogens and retain different amounts of their respective counter ions. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) images of the nanostructures showed that these systems have different morphologies depending on the acid employed during fabrication and the post preparation temperature treatment. High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) of the TCPP nanostructures indicate that those prepared in HCl are crystalline while the nanoassemblies made in TFA are polycrystalline or amorphous.

scholarly journals Magnetic-field-assisted synthesis of anisotropic iron oxide particles: Effect of pH

2020 ◽  
Vol 11 ◽  
pp. 1230-1241
Author(s):  
Andrey V Shibaev ◽  
Petr V Shvets ◽  
Darya E Kessel ◽  
Roman A Kamyshinsky ◽  
Anton S Orekhov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Building Blocks ◽  
Dipole Interaction ◽  
Iron Oxide Particles ◽  
Transmission Electron ◽  
Oxide Particles ◽  
Co Precipitation ◽  
Magnetite Nanocrystals

The synthesis of magnetite (Fe3O4) nanorods using reverse co-precipitation of Fe3+ and Fe2+ ions in the presence of a static magnetic field is reported in this work. The phase composition and crystal structure of the synthesized material were investigated using electron diffraction, Raman spectroscopy, and transmission electron microscopy. It was shown that the morphology of the reaction product strongly depends on the amount of OH− ions in the reaction mixture, varying from Fe3O4 nanorods to spherical Fe3O4 nanoparticles. Fe3O4 nanorods were examined using high-resolution transmission electron microscopy proving that they are single-crystalline and do not have any preferred crystallographic orientation along the axis of the rods. According to the data obtained a growth mechanism was proposed for the rods that consists of the dipole–dipole interaction between their building blocks (small hexagonal faceted magnetite nanocrystals), which are formed during the first step of the reaction. The study suggests a facile, green and controllable method for synthesizing anisotropic magnetic nanoparticles in the absence of stabilizers, which is important for further modification of their surfaces and/or incorporation of the nanoparticles into different media.

scholarly journals Single-component quasicrystalline nanocrystal superlattices through flexible polygon tiling rule

Science ◽  
2018 ◽  
Vol 362 (6421) ◽  
pp. 1396-1400 ◽  
Author(s):  
Yasutaka Nagaoka ◽  
Hua Zhu ◽  
Dennis Eggert ◽  
Ou Chen
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Dots ◽  
Computer Simulations ◽  
Building Blocks ◽  
Single Component ◽  
Atomic Scale ◽  
Transmission Electron ◽  
Nanocrystal Superlattices ◽  
The Creation

Quasicrystalline superlattices (QC-SLs) generated from single-component colloidal building blocks have been predicted by computer simulations but are challenging to reproduce experimentally. We discovered that 10-fold QC-SLs could self-organize from truncated tetrahedral quantum dots with anisotropic patchiness. Transmission electron microscopy and tomography measurements allow structural reconstruction of the QC-SL from the nanoscale packing to the atomic-scale orientation alignments. The unique QC order leads to a tiling concept, the “flexible polygon tiling rule,” that replicates the experimental observations. The keys for the single-component QC-SL formation were identified to be the anisotropic shape and patchiness of the building blocks and the assembly microscopic environment. Our discovery may spur the creation of various superstructures using anisotropic objects through an enthalpy-driven route.

Electron Microscopy of hydrothermally treated gamma-alumina

1990 ◽  
Vol 48 (4) ◽  
pp. 236-237
Author(s):  
S.A. Mansour ◽  
M. Halabl ◽  
R. Scholz
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Microscope ◽  
Treatment Process ◽  
Carbon Film ◽  
Alumina Powder ◽  
Gamma Alumina ◽  
Pore Characteristics ◽  
Transmission Electron ◽  
Level Information

Transmission electron microscopy (TEM) was utilized to study the microstructural changes that take place as a result of treating gamma-alumina extrudates at various temperatures for different treatment times. The value of the study comes from the numerous uses of gamma-alumina, the most important being as a support for catalysts, and from its ability to obtain valuable submicron-level information related to pore structure by TEM. The pore characteristics of the extrudates were controlled through controlling the treatment process. Extrudates were heated in an autoclave at temperatures of 150, 200 and 300°C for treatment times of 1,2,4 and 8h.A JEOL JEM-1200EX transmission electron microscope (TEM) operating at 120 kV was used. The TEM specimens were prepared by crushing the extrudates in a mortar and ultrasonically suspending the fine gamma-alumina powder in alcohol. The suspended particles were deposited on a perforated carbon film supported on a copper grid.

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