Solid NMR Spectroscopy Research Articles

Enhancing Stability of SAPO-37 Molecular Sieve through Aluminum Phosphate Utilization: Synthesis, Stability Mechanism, and Catalytic Performance.

SAPO-37 molecular sieve, characterized by its three-dimensional 12-membered-ring FAU structure, has drawn wide attention due to its unique properties and catalytic potential. However, its susceptibility to framework collapse under low-temperature and humid conditions hinders practical applications, affecting both the reaction performance and sample storage. To tackle this, we utilized aluminum phosphate as a precursor for synthesizing SAPO-37, aiming to modify Si incorporation mechanisms and improve P and Al environments. Solid NMR spectroscopy combined with other techniques proves that the resulting SAPO-37-AP has enriched silicon islands, leading to reduced water adsorption, more reversible structural change, and significantly enhanced stability after low-temperature vapor treatment compared to conventional SAPO-37. Remarkably, SAPO-37-AP, after water vapor treatment, still exhibits superior performance in the liquid-phase Beckmann rearrangement reaction. This approach enhances stability, reduces templating agent amounts, and improves the solid product yield, offering promising practical applications.

Extraction of polyphenols associated with pectin from olive waste (alperujo) with choline chloride.

The main by-product from olive oil extraction (alperujo) was extracted with hot water, citric acid, natural deep eutectic solvent (choline chloride: citric acid), and only choline chloride. The purified extracts were composed of macromolecular complexes constituting polyphenols associated with pectin. The extracts were structurally characterized by FT-IR and solid-NMR spectroscopy and an in vitro test revealed distinct antioxidant and antiproliferative activity, depending on the extracting agents. The choline chloride-extracted complex contained the highest amount of polyphenols among the examined agents, which exhibited a strong antioxidant activity and significant antiproliferative capacity. However, the complex extracted by hot water showed the highest antiproliferative capacity in vitro against the colon carcinoma Caco-2 cell line. In this finding, choline chloride could be used as a novel, green and promising alternative to the conventional extracting agent for the production of complexes that combine the antioxidant activity of phenolic compounds and the physiological effects of pectic polysaccharides.

Hydrogen generation system for fuel cells based on high pressure hydrolysis of solid-state sodium borohydride

The aim of this study was to produce sufficient hydrogen for high-power fuel cell applications through acid-accelerated hydrolysis of sodium borohydride (SBH) with liquid water. Liquid hydrolysis of SBH was performed under high temperatures (160–200 ℃) and high pressure (40 bar) conditions. The characteristics of the liquid hydrolysis of SBH were analyzed according to the feed injection rate, reactant temperature, and excess stoichiometric number. In addition, 11B solid NMR spectroscopy was conducted to analyze the composition of the reaction product. In all experimental cases, the conversion of SBH was ≥95%, and a maximum of 6.71 wt% gravimetric hydrogen density was achieved. The experimental results indicated that it is possible to control the rate of hydrogen generation through the feed injection rate. This suggests that hydrogen can be supplied to varying-output fuel cell applications using this system. In addition, as a result of experiments according to the reactant temperature, it was demonstrated that the lower the reactant temperature, the less hydrogen produced, and the greater the unreacted residual SBH. Moreover, when the excess stoichiometric ratio increased, the gravimetric hydrogen density decreased. This reduced the viscosity of the reaction product and the amount of unreacted SBH observed when the reaction was conducted at low reactant temperatures. Therefore, it is possible to consider increasing the excess stoichiometric number for practical purposes.

Nano-Structuration of WO3 Nanoleaves by Localized Hydrolysis of an Organometallic Zn Precursor: Application to Photocatalytic NO2 Abatement.

WO3 is a known photocatalytic metal oxide frequently studied for its depollution properties. However, it suffers from a high recombination rate of the photogenerated electron/holes pair that is detrimental to its performance. In this paper, we present a new chemical method to decorate WO3 nanoleaves (NLs) with a complementary metal oxide (ZnWO4) in order to improve the photocatalytic performance of the composite material for the abatement of 400 ppb NO2 under mild UV exposure. Our strategy was to synthesize WO3·2H2O nanoleaves, then, to expose them, in water-free organic solution, to an organometallic precursor of Zn(Cy)2. A structural water molecule from WO3·2H2O spontaneously decomposes Zn(Cy)2 and induces the formation of the ZnO@WO3·H2O nanocomposite. The material was characterized by electronic microscopy (SEM, TEM), TGA, XRD, Raman and solid NMR spectroscopies. A simple thermal treatment under air at 500 °C affords the ZnWO4@WO3 nanocomposite. The resulting material, additionally decorated with 1% wt. Au, presents a remarkable increase (+166%) in the photocatalytic abatement of NO2 under UV compared to the pristine WO3 NLs. This synthesis method paves the way to the versatile preparation of a wide range of MOx@WO3 nanocomposites (MOx = metal oxide).

Apple Pectin Based Hydrogel Electrolyte for Energy Storage Application

With the increase of portable power sources demand, new technologies, e.g. wearable and flexible electronics, are projected to generate $1.25 billion market by 2022.[1] New storage energy devices are more than ever in demand which requires new specifications in order to be used in those future applications. To achieve this development, we have to minimize the environmental impact in the whole battery life cycle, from conception to degradation of the system, and reduce production costs. Polymer hydrogel electrolyte are one of the promising alternative for processing new flexible batteries.[2] A great hydrogel electrolyte should promise excellent ionic transport pathways and sufficient mechanical strength, not to cause short-circuits. As a matter of fact, hydrogel electrolytes are well-known for their good ionic conductivity. Nevertheless, the original polymers used in these systems don’t take into account the cost of the environmental impact and safety due to the processing or biodegradability of those hydrogels.[3] In this study, we report a new hydrogel-based electrolyte material made by apple pectin. This presentation will mainly focus on the interactions between pectin functional groups, water and ions using solid NMR spectroscopy. Thermal properties will be discussed based on differential scanning calorimetry analysis. Electrical and electrochemical characterisctics obtained by electrochemical impedance spectroscopy, galvanostatic cycling and cyclic voltametry will demonstrate the applicability of such hydrogel electrolyte.This study could promote a great innovation in the energy storage field, by recycling one of apple peel’s component (which is the main waste in preserves manufacturing[4]) into a hydrogel electrolyte.

Novel synthesized microporous ionic polymer applications in transesterification of Jatropha curcas seed oil with short Chain alcohol

New suites of sulfonic acid-functionalized microporous ionic polymers (PIPs) catalysts were synthesized with polymer, alkyl bromides, and 1, 3-propane sultone via a two-step procedure. The synthesized microporous PIP catalysts were characterized using FT-IR, SEM-Mapping, XPS, N2 adsorption–desorption isotherms, solid NMR spectroscopy, and element analysis. Esterification of several fatty acids with ethanol, which was used as a model reaction in the stabilization of Jatropha curcas seed oil, was checked over functionalized PIP. We tested the catalytic performance of PIP-C8 on the synthesis of fatty acid esters via the transesterification of J. curcas seed oil with a mixture of short-chain alcohols such as ethanol, ethanol–to–diethyl carbonate (1;1 molar ratio), and ethanol–to–dimethyl carbonate (1:1 molar ratio) with 170 mg of PIP-C8 at reflux temperature with agitation. The PIP-C8 catalyst was particularly effective, having achieved yields of 85%, 94%, and 70% for J. curcas seed oil with ethanol, J. curcas seed oil with ethanol–to–DEC, and J. curcas seed oil with ethanol–to–DMC, respectively, under the optimized reaction conditions. The catalyst could be recycled more than five times without significant deactivation. Kinetic studies performed at different temperatures revealed that the conversion of oleic acid to an ethyl ester follows a first-order reaction. The best catalysts with microporous structure (average pore diameter: 1.7–1.9 nm, pore volume: 0.23–0.33 cm3 g–1) and –SO3H density (0.70–0.84 mmol/gcat) were obtained by 1, 3-propane sultone of the chemically activated. The results indicate that the site activity of functionalized microporous ionic polymer materials shows promising approach for the development of environmentally friendly technology.

Effect of Degradation Processes Caused by a Small Perturbation on the Growth of the Average Cluster Size of Correlated Spins in Multiple Quantum NMR Spectroscopy of Solids

Effect of Degradation Processes Caused by a Small Perturbation on the Growth of the Average Cluster Size of Correlated Spins in Multiple Quantum NMR Spectroscopy of Solids

Direct fluorination of acetyl and ethyl celluloses in perfluorinated liquid medium

Direct fluorination of acetyl- and ethylcelluloses was performed in a bubble reactor with liquid perfluorinated medium (perfluorodecalin). Concentrated fluorination mixtures (F2 + N2) and long reaction times (up to 3 h) were used for better control of the degree of fluorination than it was made previously in direct gaseous fluorination of polymers. The fluorine consumption in the runs with both polymers only slightly increased with increasing temperature and fluorine concentration in the gas mixture. Fluorine content in the fluorinated polymers did not depend strongly on the fluorination conditions. X-ray analysis, differential scanning calorimetry of the fluorinated samples showed no significant changes in respect of the initial polymers. However, emergence of novel and splitting of initial absorption bands, the change of polarization of C–O bonds in IR spectra for the fluorinated samples were observed. It can directly and indirectly justify the appearance of the C–F bonds in the side groups and glycopyranosyl ring of the fluorinated substituted celluloses.19F, 13C solid NMR spectroscopy of the fluorinated samples confirm hydrogen-substituted fluorination of methyl groups.

Constant-time 2D and 3D through-bond correlation NMR spectroscopy of solids under 60 kHz MAS.

Establishing connectivity and proximity of nuclei is an important step in elucidating the structure and dynamics of molecules in solids using magic angle spinning (MAS) NMR spectroscopy. Although recent studies have successfully demonstrated the feasibility of proton-detected multidimensional solid-state NMR experiments under ultrafast-MAS frequencies and obtaining high-resolution spectral lines of protons, assignment of proton resonances is a major challenge. In this study, we first re-visit and demonstrate the feasibility of 2D constant-time uniform-sign cross-peak correlation (CTUC-COSY) NMR experiment on rigid solids under ultrafast-MAS conditions, where the sensitivity of the experiment is enhanced by the reduced spin-spin relaxation rate and the use of low radio-frequency power for heteronuclear decoupling during the evolution intervals of the pulse sequence. In addition, we experimentally demonstrate the performance of a proton-detected pulse sequence to obtain a 3D (1)H/(13)C/(1)H chemical shift correlation spectrum by incorporating an additional cross-polarization period in the CTUC-COSY pulse sequence to enable proton chemical shift evolution and proton detection in the incrementable t1 and t3 periods, respectively. In addition to through-space and through-bond (13)C/(1)H and (13)C/(13)C chemical shift correlations, the 3D (1)H/(13)C/(1)H experiment also provides a COSY-type (1)H/(1)H chemical shift correlation spectrum, where only the chemical shifts of those protons, which are bonded to two neighboring carbons, are correlated. By extracting 2D F1/F3 slices ((1)H/(1)H chemical shift correlation spectrum) at different (13)C chemical shift frequencies from the 3D (1)H/(13)C/(1)H spectrum, resonances of proton atoms located close to a specific carbon atom can be identified. Overall, the through-bond and through-space homonuclear/heteronuclear proximities determined from the 3D (1)H/(13)C/(1)H experiment would be useful to study the structure and dynamics of a variety of chemical and biological solids.

Feasibility of arsenic and antimony NMR spectroscopy in solids: An investigation of some group 15 compounds

The feasibility of obtaining 75As and 121/123Sb NMR spectra for solids at high and moderate magnetic field strengths is explored. Arsenic-75 nuclear quadrupolar coupling constants and chemical shifts have been measured for arsenobetaine bromide and tetraphenylarsonium bromide. Similarly, 121/123Sb NMR parameters have been measured for tetraphenylstibonium bromide and potassium hexahydroxoantimonate. The predicted pseudo-tetrahedral symmetry at arsenic and the known trigonal bipyramidal symmetry at antimony in their respective tetraphenyl-bromide “salts” are reflected in the measured 75As and 121Sb nuclear quadrupole coupling constants, CQ(75As)=7.8MHz and CQ(121Sb)=159MHz, respectively. Results of density functional theory quantum chemistry calculations for isolated molecules using ADF and first-principles calculations using CASTEP, a gauge-including projector augmented wave method to deal with the periodic nature of solids, are compared with experiment. Although the experiments can be time consuming, measurements of 75As and 121Sb NMR spectra (at 154 and 215MHz, respectively, i.e., at B0=21.14T) with linewidths in excess of 1MHz are feasible using uniform broadband excitation shaped pulse techniques (e.g., WURST and WURST-QCPMG).

Cellulose based organogel as an adsorbent for dissolved organic compounds

Highly porous cellulose organogels were prepared from nanofibrillated cellulose hydrogels and their adsorption properties towards a wide range of organic pollutants were investigated. Here, we show that by functionalizing the native cellulose nanofibrils of the organogel with the hydrophobic hydrocarbon chains, the adsorption capacity is meaningfully boosted, making possible to use the modified organogel as an adsorbent for organic compounds. The chemical modification was confirmed by infrared spectroscopy (FTIR) and solid NMR spectroscopy. The kinetics and adsorption isotherms of several aromatic compounds, including herbicides were investigated. It was proposed that the adsorption process is the result of the diffusion of the organic solute inside the grafted hydrocarbon chains acting as a reservoir on which the organic compounds would be accumulated. The results showed that the modified cellulose organogels could be easily regenerated and reused without any loss of the adsorption capacity, which constitutes one of the main advantages of this category of the adsorbents derived from a renewable resource.

Synthesis, characterization and cytotoxicity of new gold(III) complexes with 1,2-diaminocyclohexane: Influence of stereochemistry on antitumor activity

Gold(III) complexes of the type [(DACH)AuCl2]Cl, derived from sodium tetrachloroaurate(III) dihydrate NaAuCl4·2H2O, where DACH is diaminocyclohexane, have been synthesized. These potential metallodrug compounds were characterized using various spectroscopic and analytical techniques, including elemental analysis, UV–Vis, infrared spectroscopy, solution as well as solid NMR spectroscopy and X-ray crystallography. The potential of the synthesized gold(III) complexes as anti-cancer agents was investigated by measuring some relevant physicochemical and biochemical properties, such as the stability of the Au–N bonds by vibrational stretching from far-IR as well as cytotoxicity and the stomach cancer cell inhibiting effect. The solid-state 13C NMR chemical shift shows that the ligand is strongly bound to the gold(III) center via N atoms. An X-ray crystallography study of the complexes shows that the cyclohexyl ring adopts a chair conformation and the gold coordination sphere adopts a distorted square planar geometry. The cis isomer in solution showed higher activity towards the inhibitory effect of human cancer cell lines such as prostate cancer (PC-3) and gastric carcinoma (SGC-7901) than that of the trans isomer. The cytotoxicity of the cis isomer complex has also been estimated in PC-3 and SGC-7901 cells.

Analyzing the adsorption of blood plasma components by means of fullerene-containing silica gels and NMR spectroscopy in solids

The results from studying the adsorption of blood plasma components (e.g., protein, triglycerides, cholesterol, and lipoproteins of low and high density) using silica gels modified with fullerene molecules (in the form of C60 or the hydroxylated form of C60(OH) x ) and subjected to hydration (or, alternatively, dehydration) are presented. The conditions for preparing adsorbents that allow us to control the adsorption capacity of silica gel and the selectivity of adsorption toward the components of blood plasma, are revealed. The nature and strength of the interactions of the introduced components (fullerene molecules and water) with functional groups on the silica surface are studied by means of solid state NMR spectroscopy (NMR-SS). Conclusions regarding the nature of the centers that control adsorption are drawn on the basis of NMR-SS spectra in combination with direct measurements of adsorption. The interaction of the oxygen of the hydroxyl group of silica gel with fullerene, leading to the formation of electron-donor complexes of C60-H, C60-OH, or C60-OSi type, is demonstrated by the observed changes in the NMR-SS spectra of silica gels in the presence of fullerene.

Crystal structure, NMR study, dc-conductivity and dielectric relaxation studies of a new compound [C2H10N2]Cd(SCN)2Cl2

The crystal structure, the solid NMR spectroscopy and the complex impedance study have been carried out on (C2H10N2)CdCl2(SCN)2. Characterization by single crystal X-ray crystallography shows that the cadmium atoms have a 2N2S2Cl hexa-coordination sphere, exhibiting pseudo-octahedral geometry. The cadmium atoms are bridged by two thiocyanate ions generating 1-D polymeric-chains. These chains are themselves interconnected by means of N-H…Cl(NCS) hydrogen bonds originating from the organic cation ((NH3)2(CH2)2) 2+ . 111 Cd isotropic chemical shifts span a range of 268ppm. The cadmium atom exhibits multiplets that result from 111 Cd- 14 N spin-spin coupling. Examination of 111 Cd and 13 C MAS line shapes shows direct measurement of the indirect spin-spin coupling constant 2 J( 111 Cd, 14 N) = 105Hz and the dipolar coupling constant of 1381Hz . Impedance spectroscopy measurements of (C2H10N2)CdCl2(SCN)2 have been studied from 209Hz to 5 MHz over the temperature range 300-370 K. The Cole-Cole (Z'' versus Z') plots are fitted to two equivalent circuits models. The formalism of complex permittivity and impedance were employed to analyze the experimental data. The dc conductivity follows the Arrhenius relation with an activation energy Ea = 0.54 (3) eV.

Properties of bacterial cellulose produced in grape medium by native isolate Gluconacetobacter sp

AbstractDuring the production of grape wine, the occurrence of thick leathery pellicle at the air‐liquid interface was found as a contaminant. The pellicle produced was investigated with a view to use as biodegradable polymer. The bacterium that is responsible for the pellicle production was isolated, characterized and identified as Gluconacetobacter sp. Pellicle was produced in pasteurized grape extract as well as in HS medium by the isolated organism in static conditions. The purified film was subjected for Fourier transform infrared spectroscopy and C13 solid NMR spectroscopy analysis, which confirmed the pellicle to be a cellulosic material. Scanning Electron Micrograph showed ultra fine network structure along with cells. The films were tested for its physicomechanical characters, barrier and thermal properties. The films of 25‐μ thickness showed very high tensile strength (41.158 MPa) and elongation of 0.987 mm. The thermal properties of the films were characterized by Differential scanning calorimetry and Thermo gravimetric analysis. The melt peak temperature was found to be 111.65°C. The percentage of weight loss was found to be 20% at 327.86°C. Barrier properties (oxygen transmission rate and water vapor transmission rate), indicated a high oxygen barrier but low water barrier. This is the first report on the barrier properties of bacterial cellulose from Gluconacetobacter sp. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

ChemInform Abstract: High-Resolution NMR of Solids

This chapter is intended to provide a bridge between the principles of NMR spectroscopy of solids and the practical execution of these experiments in the laboratory. The point of view is one of physical concepts, rather than of mathematical rigor. Interwoven with the fundamentals of solid-state NMR are practical tips garnered from laboratory experience. The presentation of material is intended to apply generally to both superconducting and electromagnet geometries. Standard experiments are emphasized, rather than the more exotic and instrument-demanding techniques. The introduction contrasts the nuclear-spin interactions (Zeeman, dipole–dipole, scalar, chemical shift) in solution and in the solid state. The section on magic-angle spinning examines the effects of mechanical specimen rotation on these nuclear-spin interactions. The concept of dipolar decoupling is introduced next, followed by a section on cross-polarization. Some of the more standard solid-state NMR experiments are described in the section ...

Efficient heteronuclear dipolar decoupling in solid-state NMR using frequency-swept SPINAL sequences

Aiming to improve heteronuclear spin decoupling efficiency in NMR spectroscopy of solids and liquid crystals, we have modified the original Small Phase Incremental ALteration (SPINAL) sequence by incorporating a frequency sweep into it. For the resulting sequence, termed SW f -SPINAL, the decoupling performance of a large number of sweep variants was explored by both numerical simulations and NMR experiments. It is found that introducing a frequency sweep generally increases both the ‘on-resonance’ decoupling performance and the robustness towards parameter offsets compared to the original SPINAL sequence. This validates the concept of extending the range of efficient decoupling by introducing frequency sweeps, which was recently suggested in the context of the frequency-swept SW f -TPPM method. The sequence found to be best performing among the SW f -SPINAL variants consists of fully swept 16 pulse pairs and is designated SW f lin (32)-SPINAL-32. Its good decoupling performance for rigid spin systems is confirmed by numerical simulations and also experimentally, by evaluating the CH 2 resonance of a powder sample of l-tyrosine under MAS. For moderate MAS frequencies, the new sequence matches the decoupling achieved with SW f -TPPM, and outperforms all other tested sequences, including TPPM and SPINAL-64. SW f lin (32)-SPINAL-32 also shows excellent decoupling characteristics for liquid crystalline systems, as exemplified by experiments on the 5CB liquid crystal.

Sensitive absorptive refocused scalar correlation NMR spectroscopy in solids

A new two-dimensional NMR experiment is described which is suitable for obtaining magic angle spinning (MAS) scalar correlation spectra in solids. The new experiment has several advantages, including increased cross peak intensities, coupled with good suppression of the diagonal. Its utility is demonstrated via assignments of the carbon-13 MAS spectra of progesterone at natural abundance and of the polymer phase of 50%-U-13C-CsC60.

Indirectly detected through-bond chemical shift correlation NMR spectroscopy in solids under fast MAS: Studies of organic–inorganic hybrid materials

Indirectly detected, through-bond NMR correlation spectra between 13C and 1H nuclei are reported for the first time in solid state. The capabilities of the new method are demonstrated using naturally abundant organic–inorganic mesoporous hybrid materials. The time performance is significantly better, almost by a factor of 10, than in the corresponding 13C detected experiment. The proposed scheme represents a new analytical tool for studying other solid-state systems and the basis for the development of more advanced 2D and 3D correlation methods.

Supercycled homonuclear dipolar decoupling in solid-state NMR: Toward cleaner H1 spectrum and higher spinning rates

A homonuclear dipolar decoupling scheme based on windowed phase-modulated Lee-Goldburg (wPMLG) pulse sequences that causes a"z-rotation" of the spins for high-resolution proton NMR spectroscopy of solids is described and analyzed. This supercycled scheme suppresses the effect of pulse imperfections on the spectra and significantly relaxes the off-resonance dependence of the line-narrowing efficiency and scale factor. This leads to a broad spectral window that is free of artifacts such as zero lines, image peaks, and localized rotor-radio-frequency resonances. High-resolution (1)H spectra and two-dimensional homonuclear (1)H-(1)H correlation spectra of standard amino acids, obtained by a combination of this supercycled scheme with magic angle spinning frequencies up to 25 kHz, are demonstrated.