Solid State NMR Spectroscopy a Valuable Technique for Structural Insights of Advanced Thin Film Materials: A Review

Solid-state NMR has proven to be a versatile technique for studying the chemical structure, 3D structure and dynamics of all sorts of chemical compounds. In nanotechnology and particularly in thin films, the study of chemical modification, molecular packing, end chain motion, distance determination and solvent-matrix interactions is essential for controlling the final product properties and applications. Despite its atomic-level research capabilities and recent technical advancements, solid-state NMR is still lacking behind other spectroscopic techniques in the field of thin films due to the underestimation of NMR capabilities, availability, great variety of nuclei and pulse sequences, lack of sensitivity for quadrupole nuclei and time-consuming experiments. This article will comprehensively and critically review the work done by solid-state NMR on different types of thin films and the most advanced NMR strategies, which are beyond conventional, and the hardware design used to overcome the technical issues in thin-film research

ELASTIC AND ULTIMATE BEHAVIOUR OF WAFFLE SLAB STRUCTURES.

In this dissertation the author investigates the behaviour of reinforced and prestressed concrete waffle slabs from initial to collapse load. The theoretical treatment covering the whole range of load, is divided into three parts: elastic analysis, ultimate analysis, and progressive failure analysis. The elastic analysis part is based on a Fourier series solution for simply supported slabs and this is extended to continuous waffle slab structures. The ultimate limit state analysis is obtained by adopting the yield line theory as an upper bound solution. The progressive failure analysis is tackled by the finite element method as a numerical technique; beyond the initiation of the first crack at sections of maximum stresses, an iterative incremental procedure is adopted to take into account the reduction of rigidities with the corresponding increment of loading, thus converting the non-linear problem into a series of incrementally linear problems in the elastic-plastic range. Comparison of results is made between skew and rectangular waffle slabs as well as between continuous slabs on isolated supports and on continuous line-supports. A study of the effect of rotating the isolated column support line about the center of the bridge on the structural response is undertaken. The theoretical analyses are substantiated and verified by experimental results obtained from tests on seven models of reinforced and prestressed concrete waffle slab bridges. The deflections and strains obtained from the tests are found to be in good agreement with the theoretical solutions. From this study it is concluded that the yield-line analysis is simple and reliable in predicting the ultimate load of waffle slab structures. Furthermore, prestressed concrete waffle slab construction is well suited for use in large span structures. Also, in predicting the collapse load of waffle slab structures, it is found that the progressive failure analysis of such structures gives results which are in close agreement with those obtained from the tests as well as from the yield-line analysis.Dept. of Civil and Environmental Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1982 .S422. Source: Dissertation Abstracts International, Volume: 43-07, Section: B, page: 2279. Thesis (Ph.D.)--University of Windsor (Canada), 1982

A study on the characteristics of Algerian Hassi-Messaoud asphaltenes:Algerian Hassi-Messaoud asphaltenes: solubility and precipitation

This study focuses on detailed characterizations of asphaltene fractions extracted from the Algerian Hassi-Messaoud oil field. It was found that the extracted asphaltenes are not completely soluble in toluene, instead two fractions of asphaltenes were obtained upon solubilizing the heptane-precipitated neat asphaltenes in toluene. Extensive characterizations of the toluene-soluble and insoluble fractions were carried out using elemental analysis, Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and solid-state nuclear magnetic resonance (ssNMR). It was suggested that the high oxygen content and uneven compositional structures are the main contributors to asphaltene instability. The toluene-insoluble fractions were found to have higher polarity and aromaticity as well as more oxygen content than the neat asphaltenes and toluene-soluble fractions

Solid-state NMR spectroscopy insights for resolving different water pools in alginate hydrogels

Alginate hydrogels are versatile self-assembling biocompatible materials with diverse biomedical and food industrial applications, which includes uses in encapsulation, (drug) delivery and tissue engineering. Hydrogel formation requires cross-linking, which for alginates is often done with calcium ions that engage in specific interactions with the polysaccharide carboxylic acid groups. Water molecules also hydrate these alginate groups and fill macropores within the hydrogels, with implications for both mechanical properties and cargo encapsulation. Understanding these aspects of hydrogels requires the observation and characterization of the hydrogel waters, how they engage the alginate, and fill the macropores. Here we employed solid-state NMR (ssNMR) spectroscopy to detect and study water molecules in re-hydrated alginate hydrogels. 1H, 2H, and 13C magic angle spinning (MAS) NMR and relaxation measurements were combined to observe both water and alginate. Two different water phases were detected that vary upon gradual (re)hydration of the alginate hydrogels. These water pools differ in their chemical shifts and NMR relaxation properties, reflecting hydration waters directly associated with the carbohydrate polymers alongside dynamic waters in the macropores. Thus, the ssNMR detects the water-filled macropore water pools and how they vary upon calcium cross-linking. We also observe how calcium cross-linking selectively immobilizes the α-guluronate monosaccharides, but leaves the β-mannuronate units more flexible and prone to selective re-hydration. Thus, these ssNMR experiments can be used to probe cross-linking and hydration of alginate hydrogels, with implications for our understanding of design parameters that tune their performance in (drug) delivery and other food industrial applications

Binder-free zeolite Beta beads with hierarchical porosity:Synthesis and application as heterogeneous catalysts for anisole acylation

Three zeolites (H-Beta, H-ZSM-5 and H-Y) were synthesized in the form of binder-free macroscopic beads (350-800 µm) using a hydrothermal method employing anion-exchange resin beads as hard template. The beads obtained after removal of the hard template by calcination consisted of crystalline zeolite domains connected with each other to form a hierarchical porous network in which the zeolitic micropores are accessible through meso- and macropores, as proven by characterization with XRD, N2 physisorption, SEM, and TEM. The composition, the nature and amount of acid sites and the degree of hydrophobicity of these beads were investigated by means of XRF, solid-state NMR, pyridine-FTIR and TGA. The zeolite beads were tested as heterogeneous catalysts in the Friedel-Crafts acylation of anisole with acetic anhydride to produce para-methoxyacetophenone. H-Beta-Beads displayed the best catalytic performance with 95% conversion of acetic anhydride and 76% yield of para-methoxyacetophenone in a batch reactor test (90 °C, 6 h). Next, the catalytic performance of H-Beta-Beads was compared in both batch and continuous-flow mode to extrudates prepared by mixing zeolite Beta powder with either kaolin or bentonite binders. H-Beta-Beads outperformed the extrudates in batch-mode reactions and could be reused in multiple runs without discernible loss of activity. In the continuous-flow test, H-Beta-Beads demonstrated higher average activity but deactivated more rapidly than the extrudates

Insights into the Characterization of the Self-Assembly of Different Types of Amphiphilic Molecules Using Dynamic Light Scattering

The self-assembly of cetyltrimethylammonium bromide, sodium dodecylsulfate, Triton X-100, and sulfobetaine surfactants in aqueous solutions was examined by dynamic light scattering, both in the presence and absence of 0.1 M NaCl salt, across various temperatures. For each surfactant, critical parameters, such as concentration and phase transition temperatures, of micelles were determined by monitoring changes in the hydrodynamic diameter with concentration and temperature. Additionally, we explored the self-assembly behavior of these surfactants when they are introduced alongside polystyrene nanoparticles. Our findings enabled the elucidation of surfactant molecule adsorption mechanisms onto polystyrene nanoparticle surfaces. Furthermore, by analyzing variations in the z-average diameter and zeta potential, we were able to establish the Krafft point, a parameter that remains imperceptible when polystyrene nanoparticles are absent from the solution.</p

Synergistic Catalytic Effects of Alloys of Noble Metal Nanoparticles Supported on Two Different Supports:Crystalline Zeolite Sn-Beta and Carbon Nanotubes for Glycerol Conversion to Methyl Lactate

Two multifunctional catalytic systems comprising Sn-based/doped crystalline zeolite Beta were synthesized, and they were employed as heterogeneous catalysts in the selective conversion of glycerol to methyl lactate. The first catalytic system, named Au-Pd-Sn-deAl-7.2-Beta-DP, was created through the post-synthesis dealumination of the parent zeolite Beta (Si/Al = 10) using 7.2 M HNO3. Subsequently, it was grafted with 27 mmol of SnCl4, resulting in Sn-deAl-7.2-Beta. Following this, Au and Pd nanoparticles were supported on this catalyst using the deposition–precipitation (DP) method. The second catalytic system was a physical mixture of Au and Pd nanoparticles supported on functionalized carbon nanotubes (Au-Pd-F-CNTs) and Sn-containing zeolite Beta (Sn-deAl-7.2-Beta). Both catalytic systems were employed in glycerol partial oxidation to methyl lactate under the following conditions: 140 °C for 4.5 h under an air pressure of 30 bar. The Au-Pd-Sn-deAl-7.2-Beta-DP catalytic system demonstrated 34% conversion of glycerol with a 76% selectivity for methyl lactate. In contrast, the physical mixture of Au-Pd-F-CNTs and Sn-deAl-7.2-Beta exhibited higher activity, achieving 58% glycerol conversion and a nearly identical selectivity for methyl lactate (77%). The catalytic results and catalyst structure were further analyzed using various characterization techniques, such as X-ray diffraction (XRD), N2 physisorption, scanning electron microscopy (SEM), X-ray fluorescence (XRF), transmission electron microscopy (TEM), UV-vis spectroscopy, and pyridine Fourier transform infrared (FTIR). These analyses emphasized the significance of adjusting the quantity of active sites, particle size, and active sites proximity under the chosen reaction conditions.</p

Synergistic Catalytic Effects of Alloys of Noble Metal Nanoparticles Supported on Two Different Supports:Crystalline Zeolite Sn-Beta and Carbon Nanotubes for Glycerol Conversion to Methyl Lactate

Two multifunctional catalytic systems comprising Sn-based/doped crystalline zeolite Beta were synthesized, and they were employed as heterogeneous catalysts in the selective conversion of glycerol to methyl lactate. The first catalytic system, named Au-Pd-Sn-deAl-7.2-Beta-DP, was created through the post-synthesis dealumination of the parent zeolite Beta (Si/Al = 10) using 7.2 M HNO3. Subsequently, it was grafted with 27 mmol of SnCl4, resulting in Sn-deAl-7.2-Beta. Following this, Au and Pd nanoparticles were supported on this catalyst using the deposition–precipitation (DP) method. The second catalytic system was a physical mixture of Au and Pd nanoparticles supported on functionalized carbon nanotubes (Au-Pd-F-CNTs) and Sn-containing zeolite Beta (Sn-deAl-7.2-Beta). Both catalytic systems were employed in glycerol partial oxidation to methyl lactate under the following conditions: 140 °C for 4.5 h under an air pressure of 30 bar. The Au-Pd-Sn-deAl-7.2-Beta-DP catalytic system demonstrated 34% conversion of glycerol with a 76% selectivity for methyl lactate. In contrast, the physical mixture of Au-Pd-F-CNTs and Sn-deAl-7.2-Beta exhibited higher activity, achieving 58% glycerol conversion and a nearly identical selectivity for methyl lactate (77%). The catalytic results and catalyst structure were further analyzed using various characterization techniques, such as X-ray diffraction (XRD), N2 physisorption, scanning electron microscopy (SEM), X-ray fluorescence (XRF), transmission electron microscopy (TEM), UV-vis spectroscopy, and pyridine Fourier transform infrared (FTIR). These analyses emphasized the significance of adjusting the quantity of active sites, particle size, and active sites proximity under the chosen reaction conditions.</p

Synergistic Catalytic Effects of Alloys of Noble Metal Nanoparticles Supported on Two Different Supports:Crystalline Zeolite Sn-Beta and Carbon Nanotubes for Glycerol Conversion to Methyl Lactate

Two multifunctional catalytic systems comprising Sn-based/doped crystalline zeolite Beta were synthesized, and they were employed as heterogeneous catalysts in the selective conversion of glycerol to methyl lactate. The first catalytic system, named Au-Pd-Sn-deAl-7.2-Beta-DP, was created through the post-synthesis dealumination of the parent zeolite Beta (Si/Al = 10) using 7.2 M HNO3. Subsequently, it was grafted with 27 mmol of SnCl4, resulting in Sn-deAl-7.2-Beta. Following this, Au and Pd nanoparticles were supported on this catalyst using the deposition–precipitation (DP) method. The second catalytic system was a physical mixture of Au and Pd nanoparticles supported on functionalized carbon nanotubes (Au-Pd-F-CNTs) and Sn-containing zeolite Beta (Sn-deAl-7.2-Beta). Both catalytic systems were employed in glycerol partial oxidation to methyl lactate under the following conditions: 140 °C for 4.5 h under an air pressure of 30 bar. The Au-Pd-Sn-deAl-7.2-Beta-DP catalytic system demonstrated 34% conversion of glycerol with a 76% selectivity for methyl lactate. In contrast, the physical mixture of Au-Pd-F-CNTs and Sn-deAl-7.2-Beta exhibited higher activity, achieving 58% glycerol conversion and a nearly identical selectivity for methyl lactate (77%). The catalytic results and catalyst structure were further analyzed using various characterization techniques, such as X-ray diffraction (XRD), N2 physisorption, scanning electron microscopy (SEM), X-ray fluorescence (XRF), transmission electron microscopy (TEM), UV-vis spectroscopy, and pyridine Fourier transform infrared (FTIR). These analyses emphasized the significance of adjusting the quantity of active sites, particle size, and active sites proximity under the chosen reaction conditions.</p