Microscopie RMN en phases liquide et solide par gradients de champ radiofréquence

NANCY1-SCD Sciences & Techniques (545782101) / SudocSudocFranceF

Water State Study of Wood Structure of Four Hardwoods Below Fiber Saturation Point with Nuclear Magnetic Resonance

Nuclear magnetic resonance (NMR) is a useful, powerful, and noninvasive technique to study the dynamics of wood-water relations, both quantitatively and qualitatively. The main objective of this study was to use NMR to characterize the state of water below the FSP. Two tropical hardwood species, huayruro (Robinia coccinea Aublet) and cachimbo (Cariniana domesticata [C. Martius] Miers), a plantation-grown eucalyptus species (Eucalyptus saligna Smith), and a temperate species, red oak (Quercus rubra L.), were studied. These species were chosen for their diversity in terms of anatomical and physical properties. Desorption tests were carried out at 21°C in a single-step procedure from full saturation state for huayruro, cachimbo, and red oak and from green condition for E. saligna. Discrete T2 times were obtained for each species and equilibrium moisture content (EMC). The results showed that even under EMC, there was a region in the hygroscopic range in which the loss of bound water takes place before all liquid water was drained. This region varies according to wood species. Furthermore, variation in the fast T2 values among the different wood species gives an indication of how bound water is distributed and arranged in sorption sites

Use of Solid-State NMR Spectroscopy for the Characterization of Molecular Structure and Dynamics in Solid Polymer and Hybrid Electrolytes

Solid-state NMR spectroscopy is an established experimental technique which is used for the characterization of structural and dynamic properties of materials in their native state. Many types of solid-state NMR experiments have been used to characterize both lithium-based and sodium-based solid polymer and polymer–ceramic hybrid electrolyte materials. This review describes several solid-state NMR experiments that are commonly employed in the analysis of these systems: pulse field gradient NMR, electrophoretic NMR, variable temperature T1 relaxation, T2 relaxation and linewidth analysis, exchange spectroscopy, cross polarization, Rotational Echo Double Resonance, and isotope enrichment. In this review, each technique is introduced with a short description of the pulse sequence, and examples of experiments that have been performed in real solid-state polymer and/or hybrid electrolyte systems are provided. The results and conclusions of these experiments are discussed to inform readers of the strengths and weaknesses of each technique when applied to polymer and hybrid electrolyte systems. It is anticipated that this review may be used to aid in the selection of solid-state NMR experiments for the analysis of these systems

Coordination-driven self-assembly of polyoxometalates into discrete supramolecular triangles

Pd(II)-directed self-assembly of a 3-pyridyl grafted Lindqvist hexavanadate led to the formation of a unique trimeric species, as confirmed by a variety of techniques, including pulsed-field gradient NMR spectroscopy and high-resolution ESI mass spectrometry