Journal ArticleDOI
Heteronuclear decoupling in rotating solids
Andrew E. Bennett,Chad M. Rienstra,Michèle Auger,Michèle Auger,K. V. Lakshmi,K. V. Lakshmi,Robert G. Griffin +6 more
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In this article, a simple two pulse phase modulation (TPPM) scheme was proposed to reduce the residual linewidths arising from insufficient proton decoupling power in double resonance magic angle spinning (MAS) experiments.Abstract:
A simple two pulse phase modulation (TPPM) scheme greatly reduces the residual linewidths arising from insufficient proton decoupling power in double resonance magic angle spinning (MAS) experiments. Optimization of pulse lengths and phases in the sequence produces substantial improvements in both the resolution and sensitivity of dilute spins (e.g., 13C) over a broad range of spinning speeds at high magnetic field. The theoretical complications introduced by large homo‐ and heteronuclear interactions among the spins, as well as the amplitude modulation imposed by MAS, are explored analytically and numerically. To our knowledge, this method is the first phase‐switched sequence to exhibit improvement over continuous‐wave (cw) decoupling in a strongly coupled homogeneous spin system undergoing sample spinning.read more
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Phase Evolution in Methylammonium Tin Halide Perovskites with Variable Temperature Solid-State 119Sn NMR Spectroscopy
Michelle Ha,Abhoy Karmakar,Guy M. Bernard,Enoc Basilio,Arun Krishnamurthy,Abdelrahman M. Askar,Karthik Shankar,Scott Kroeker,Vladimir K. Michaelis +8 more
TL;DR: Hybrid organic-inorganic metal-halide perovskite materials are an emerging class of materials that could profoundly change the optoelectronic and solar absorber research fields as discussed by the authors.
Journal ArticleDOI
Synthesis and characterization of novel polyampholyte and polyelectrolyte polymers containing imidazole, triazole or pyrazole
Juan Manuel Lázaro Martínez,Juan Manuel Lázaro Martínez,Ana Karina Chattah,Rosa Maria Torres Sanchez,Graciela Buldain,Viviana Campo Dall’ Orto +5 more
TL;DR: In this article, a one-spot synthetic strategy was used to obtain methacrylic acid, ethylene glycol diglycidyl ether and pyrazole, triazole or imidazole.
Journal ArticleDOI
Modification of the Stöber Process by a Polyazamacrocycle Leading to Unusual Core−Shell Silica Nanoparticles
Sylvie Masse,Guillaume Laurent,Françoise Chuburu,Cyril Cadiou,Isabelle Déchamps,Thibaud Coradin +5 more
TL;DR: The encapsulation of 1,4,7,10-tetraazacyclododecane (cyclen) within silica nanoparticles using the Stöber process was studied and it is suggested that the particle core is constituted of hybrid primary nanoparticles resulting from cyclen-silica interactions, whereas the shell formation results from further condensation of unreacted silica precursors.
Journal ArticleDOI
High‐Resolution Solid‐State NMR Structure of an Anticancer Agent
TL;DR: It is demonstrated that solid‐state NMR methods can be used to rapidly determine the high‐resolution 3D structure of Epothilone B in the polycrystalline state and the results pave the way to the study of ligand–microtubule interactions in a noncrystaline and insoluble environment at atomic level.
Journal ArticleDOI
Improving sustained drug delivery from ophthalmic lens materials through the control of temperature and time of loading.
Ana Topete,Andreia Sofia Oliveira,Anabela C. Fernandes,Teresa G. Nunes,Ana Paula Serro,Benilde Saramago +5 more
TL;DR: The in vivo efficacy of CI26Y samples, drug loaded at 60 °C for two weeks, was predicted using a simplified mathematical model to estimate the drug concentration in the aqueous humor and the estimated concentrations were found to comply with the therapeutic needs, at least, for moxifloxacin and diclofenac.
References
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Journal ArticleDOI
Proton‐enhanced NMR of dilute spins in solids
TL;DR: In this article, the NMR signals of isotopically or chemically dilute nuclear spins S in solids can be enhanced by repeatedly transferring polarization from a more abundant species I of high abundance (usually protons) to which they are coupled.
Book
Principles of high-resolution NMR in solids
Abstract: 1 Introduction.- 2 Nuclear Spin Interactions in Solids.- 2.1 Basic Nuclear Spin Interactions in Solids.- 2.2 Spin Interactions in High Magnetic Fields.- 2.3 Transformation Properties of Spin Interactions in Real Space.- 2.4 Powder Spectrum Line Shape.- 2.5 The NMR Spectrum. Lineshapes and Moments.- 2.6 Magic Angle Spinning (MAS).- 2.7 Rapid Anisotropic Molecular Rotation.- 2.8 Line Shapes in the Presence of Molecular Reorientation.- 3 Multiple-Pulse NMR Experiments.- 3.1 Idealized Multiple-Pulse Sequences.- 3.2 The Four-Pulse Sequence (WHH-4).- 3.3 Coherent Averaging Theory.- 3.4 Application of Coherent Averaging Theory to Multiple-Pulse Sequences.- 3.5 Arbitrary Rotations and Finite Pulse Width in Multiple-Pulse Experiments.- 3.6 Second Averaging.- 3.7 The Influence of Pulse Imperfections on Multiple-Pulse Experiments.- 3.8 Resolution of Multiple-Pulse Experiments.- 3.9 Magic Angle Rotating Frame Line Narrowing Experiments.- 3.10 Modulation Induced Line Narrowing.- 3.11 Applications of Multiple-Pulse Experiments.- 4 Double Resonance Experiments.- 4.1 Basic Principles of Double Resonance Experiments.- 4.2 Cross-Polarization of Dilute Spins.- 4.3 Cross-Polarization Dynamics.- 4.4 Spin-Decoupling Dynamics.- 4.5 Application of Cross-Polarization Experiments.- 5 Two-Dimensional NMR Spectroscopy.- 5.1 Basic Principles of 2 D-Spectroscopy.- 5.2 2D-Spectroscopy of 13C-1H Interactions in Solids.- 5.3 Applications of 2D-Spectroscopy.- 6 Multiple-Quantum NMR Spectroscopy.- 6.1 Double-Quantum Decoupling.- 6.2 The Three-Level System Double Quantum Coherence.- 6.3 Multiple-Quantum Coherence.- 6.4 Selective Multiple-Quantum Coherence.- 6.5 Double-Quantum Cross-Polarization.- 7 Magnetic Shielding Tensor.- 7.1 Ramsey's Formula.- 7.2 Approximate Calculations of the Shielding Tensor.- 7.3 Proton Shielding Tensors.- 7.4 19F Shielding Tensors.- 7.5 13C Shielding Tensors.- 7.6 Other Shielding Tensors.- 8 Spin-Lattice Relaxation.- 8.1 Spin-Lattice Relaxation in the Weak Collision Limit.- 8.2 Spin-Lattice Relaxation in Multiple-Pulse Experiments.- 8.3 Application of Multiple-Pulse Experiments to the Investigation of Spin-Lattice Relaxation.- 8.4 Spin-Lattice Relaxation in Dilute Spin Systems.- 8.5 Selective Excitation and Spectral Diffusion.- 9 Appendix.- A Irreducible Tensor Representation of Spin Interactions.- B Rotations.- C General Line Shape Theory.- D Homogeneous, Inhomogeneous and Heterogeneous Lineshapes.- E Lineshape and Relaxation due to Fluctuating Chemical Shift Tensors.- F Time Evolution and Magnus Expansion.- G Coherent Versus Secular Averaging Theory.- H Applications of Average Hamiltonian Theory.- I Relaxation Theory.- 10 References.- 11 Subject Index.
Journal ArticleDOI
Nuclear Magnetic Resonance Spectra from a Crystal rotated at High Speed
TL;DR: In this article, it was shown that when these weak side-spectra are included the second moment does indeed remain invariant even though the second moments of the central portion, which is all that is observed experimentally, becomes smaller.
Journal ArticleDOI
Carbon-13 nuclear magnetic resonance of polymers spinning at the magic angle
Journal ArticleDOI
An improved sequence for broadband decoupling: WALTZ-16
TL;DR: In this paper, the effects of the proton irradiation sequence by means of a train of spin rotation operators, the overall effect at the end of the cycle being calculated by explicit matrix multiplication, the offset dependence of this proton response determined the residual splitting of the carbon-13 resonance and hence the effectiveness of the decoupling.