Broadband excitation in solid-state NMR of paramagnetic samples using Delays Alternating with Nutation for Tailored Excitation ('Para-DANTE')

This Letter shows that interleaved sequences of short pulses in the manner of 'Delays Alternating with Nutation for Tailored Excitation' (DANTE) with N = 1,2,3 . . . equidistant pulses per rotor period extending over K rotor periods can be used to excite, invert or refocus a large number of spinning sidebands of spin-1/2 nuclei in paramagnetic samples where hyperfine couplings lead to very broad spectra that extend over more than 1 MHz. The breadth of the response is maintained for rf-field amplitudes as low as 30 kHz since it results from cumulative effects of individual pulses with very short durations

Mesoporous Silica Nanoparticles Loaded with Surfactant: Low Temperature Magic Angle Spinning 13C and 29Si NMR Enhanced by Dynamic Nuclear Polarization

We show that dynamic nuclear polarization (DNP) can be used to enhance NMR signals of13C and 29Si nuclei located in mesoporous organic/inorganic hybrid materials, at several hundreds of nanometers from stable radicals (TOTAPOL) trapped in the surrounding frozen disordered water. The approach is demonstrated using mesoporous silica nanoparticles (MSN), functionalized with 3-(N-phenylureido)propyl (PUP) groups, filled with the surfactant cetyltrimethylammonium bromide (CTAB). The DNP-enhanced proton magnetization is transported into the mesopores via 1H–1H spin diffusion and transferred to rare spins by cross-polarization, yielding signal enhancements εon/off of around 8. When the CTAB molecules are extracted, so that the radicals can enter the mesopores, the enhancements increase to εon/off ≈ 30 for both nuclei. A quantitative analysis of the signal enhancements in MSN with and without surfactant is based on a one-dimensional proton spin diffusion model. The effect of solvent deuteration is also investigated

Homogeneous broadenings in 2D solid-state NMR of half-integer quadrupolar nuclei

The question of the homogeneous broadening that occurs in 2D solid-state NMR experiments is examined. This homogeneous broadening is mathematically introduced in a simple way, versus the irreversible decay rates related to the coherences that are involved during t1 and t2. We give the pulse sequences and coherence transfer pathways that are used to measure these decay rates. On AlPO4 berlinite, we have measured the 27Al echo-type relaxation times of the central and satellite transitions on 1Q levels, so that of coherences that are situated on 2Q, 3Q, and 5Q levels. We compare the broadenings that can be deduced from these relaxation times to those directly observed on the isotropic projection of berlinite with multiple-quantum magic-angle spinning (MAS), or satellite-transition MAS. We show that the choice of the high-resolution method, should be done according to the spin value and the corresponding homogeneous broadening

Nouvelles méthodes de RMN des solides pour l'élucidation de la structure des tamis moléculaires importants en catalyse : Résonance magnétique nucléaire

Notre approche des catalyseurs a impliqué les nouveaux développements liés à 4 nouvelles méthodes en RMN des solides : MQMAS (Multi-Quanta Magic-Angle Spinning), REDOR (Rotational-Echo Double-Resonance), REAPDOR (Rotational-Echo Adiabatic-Passage Double-Resonance), et MQ-REDOR (Multi-Quanta REDOR). Ces méthodes ont été appliquées à des tamis moléculaires importants d'un point de vue structural et catalytique. Un des principaux buts de ces études a été l'élucidation des caractéristiques structurales, telles que l'organisation des sites Tétraédriques (T) et la localisation des cations dans les canaux des nouveaux matériaux synthétisés au National Chemical Laboratory (NCL) de Pune (Inde). Le principal objectif de ces travaux a été d'analyser les caractéristiques structurales de façon quantitative afin d'aboutir à une meilleure compréhension des propriétés catalytiques uniques montrées par ces matériaux. Ce projet a 'marié' les nouveaux matériaux développés au NCL avec les nouvelles méthodes de RMN des solides mises au point à Lille

Etude des connectivités interatomiques dans les solides par résonance magnétique nucléaire

LILLE1-BU (590092102) / SudocSudocFranceF

Resolution enhancement in 1D solid-state NMR spectra of spin-9/2 quadrupolar nuclei

NMR is an insensitive spectroscopy, which often requires numerous accumulations, especially for 2D high-resolution methods (MQMAS and STMAS) for quadrupolar nuclei in solids. This may be a very important limitation for the case of insensitive nuclei, where a 1D spectrum with better resolution than the central-transition is then highly desirable. This problem has been addressed for the case of spin-5/2 nuclei by the Double-Quantum Filtered Satellite Transition Spectroscopy: DQF-SATRAS-ST1. We extend this concept to the spin-9/2 nuclei with the SATRAS-ST2 method. This method allows the observation of 1D spectra with a much better resolution than that observed in the isotropic projection of 2D MQ/ST1-MAS spectra. This enhanced resolution results from the much smaller homogeneous broadening that occurs on the SATRAS-ST2 method as compared to MQ/ST1-MAS spectra. The main interest in this method is for well-crystallized samples

Dealing with Quadrupolar Nuclei in Paramagnetic Systems

International audienceQuadrupolar nuclei with spin quantum number I > 1/2, e.g. 7Li, 23Na and 17O, are frequently encountered in lithium-ion batteries and sodium-ion batteries. This chapter describes: (i) the basic theory, (ii) the powder sample line-shapes with first- and second-order quadrupolar broadening observed under static or MAS conditions, (iii) some important experimental techniques such as MQMAS, and finally (iv) the developments of correlation NMR experiments. In recent years, solid-state nuclear magnetic resonance spectroscopy (SS-NMR) has become a vital analytical method that provides atomic-level structural information of materials used for Li-ion and Na-ion batteries.1 In these materials, 7Li, 23Na and 17O isotopes are frequently encountered, which are typical quadrupolar nuclei with spin quantum number I > 1/2. In fact, quadrupolar nuclei account for ca. 75% of all NMR-active nuclei in the periodic table, and they are very important for SS-NMR structural analyses. This chapter describes: (i) the basic theory, (ii) the powder sample line-shapes with first- and second-order quadrupolar broadening observed under static or MAS conditions, (iii) some important experimental techniques such as MQMAS, and finally (iv) the developments of correlation NMR experiments

Méthodes d'analyse structurale par RMN haute résolution des noyaux quadripolaires et mesures des couplages à travers les liaisons et l'espace

Nous présentons ici les dernières techniques de RMN du solide de haute résolution sur les noyaux quadripolaires telles que le MQMAS, le STMAS, l'I-STMAS et quelques unes de leurs variantes. Nous insistons sur les limitations expérimentales de chacune. Dans un deuxième temps, nous décrivons le FS-J-RES qui pennet de mesurer précisément et sélectivement le couplage Jhétéronuc1éaire entre deux noyaux dont l'un peut être quadripolaire. Nous analysons en détail l'influence du pulse long sélectif fréquentiellement, notamment en présence de CSA sur le spin non observé. Cela nous permet d'introduire une formule analytique simple qui rend compte de la plupart des paramètres expérimentaux. Enfin, nous étendons la technique de mesure sélective de couplage dipolaire FS-REDOR au systèmes comportants un noyau quadripolaire. Nous analysons l'effet des pulses, en particulier en présence de CSA. Des résultats expérimentaux sont présentés sur l'histidine, la glycine et l'AIPO4 VPI5.LILLE1-BU (590092102) / SudocSudocFranceF