Revisiting Alkoxysilane Assembly on Silica Surfaces: Grafting versus Homo-Condensation in Solution.

Silica surface functionalization is often done through the condensation of functional silanes on silanols, silica surfaces' terminal groups. APTES, aminopropyltriethoxysilane, is widely used due to its assumed high reactivity with silanols, kinetically promoted by the catalytic action of the terminal amine function. Here, we revisit, based on a quantitative analysis by solid-state Si NMR, the assembly of this silane on silica surfaces to investigate whether its presence results from grafting, i.

Incorporation of vanadium into the framework of hydroxyapatites: importance of the vanadium content and pH conditions during the precipitation step.

Even though vanadium-modified hydroxyapatite (V-HAp) samples are very promising systems for oxidative dehydrogenation of propane, the incorporation of vanadium into the hydroxyapatite framework was reported to be limited and to lead to over-stoichiometric compounds. Here, the synthesis of a Ca(PO)(VO)(OH) stoichiometric solid solution using a co-precipitation method is monitored in the whole composition range (0 ≤ x ≤ 6) by controlling the pH of the precipitation medium, with continuous (the first series of samples) or periodic (the second series of samples) addition of NHOH during the precipitation step or during the maturation step, respectively. It is demonstrated that the changes in pH conditions result in materials of a substantial difference in terms of the final composition.

Identification of the silver state in the framework of Ag-containing zeolite by XRD, FTIR, photoluminescence, Ag NMR, EPR, DR UV-vis, TEM and XPS investigations.

Silver has been identified in the framework of AgSiBEA zeolites (where x = 3-6 Ag wt%) by the combined use of XRD, Ag MAS NMR, FTIR, diffuse reflectance UV-visible, EPR and XPS spectroscopy. The incorporation of Ag ions into the framework of SiBEA zeolite has been evidenced by XRD. The consumption of OH groups as a result of their reaction with the silver precursor has been monitored by FTIR and photoluminescence spectroscopy.

NMR cogwheel phase cycling determination with web tools: amplitude-modulated z-filter MQMAS sequence.

Our recent method based on the use of web tools (XML and XSLT) for constructing cogwheel phase cycles is extended to the selection of two symmetrical coherence transfer pathways in the case of an amplitude-modulated z-filter MQMAS sequence. For all spins (I=3/2, 5/2, 7/2 and 9/2) and all MQ experiments we compare cogwheel phase cycling with the traditional "nested" phase cycling. The principal difference in the number of phase cycling steps lies in the use of digitizer phase.

DFT-NMR Investigation and (51)V 3QMAS experiments for probing surface oh ligands and the hydrogen-bond network in a polyoxovanadate cluster: the case of Cs(4)[H(2)V(10)O(28)].4H(2)O.

This work shows that the combination of first-principles calculations and (51)V NMR experiments is a powerful tool to elucidate the location of surface hydroxyl groups and to precisely describe the hydrogen bond network in the complex decavanadate cluster Cs(4)[H(2)V(10)O(28)].4H(2)O, enhancing the strength of NMR crystallography. The detailed characterization of H-bond networks for these kinds of inorganic compounds is of primary importance and should benefit from the DFT-NMR predictions by considering explicitly the periodic boundary conditions.

Determination of NMR cogwheel phase cycle with XML.

The selection of correct coherence transfer pathways is an essential component of an NMR pulse sequence. This article describes a new method based on the use of web tools (eXtensible Markup Language and eXtensible Stylesheet Language Transformation) to generate a cogwheel phase cycle for selecting coherence transfer pathways. We illustrate this method with the three-pulse phase-modulated shifted-echo or split-t(1) MQMAS sequences for triple-quantum spin-3/2 systems.

[French nationwide survey of abstinence-oriented treatments in opiate-addicted patients. Results at 12 months].

Unlabelled: Over the last few years, general practitioners and pharmacists in France have become more directly involved in the treatment of opiate-addicted patients with the rapid development of office-based buprenorphine and methadone maintenance programs. At the same time, demand for abstinence-oriented interventions outside established maintenance programs continues to be addressed to the primary care system.

Method: Our prospective and multicentric survey was conducted to monitor the follow-up of such abstinence-oriented interventions during a 12 months period, by means of questionnaires investigating the psychosocial, medical and addictive status of the patients recruited.

Procedures for labeling the high-resolution axis of two-dimensional MQ-MAS NMR spectra of half-integer quadrupole spins.

The increasing development and application of the multiple-quantum MAS NMR for half-integer quadrupole spins has led to various RF pulse sequences for improving the excitation of multiple-quantum coherences and their conversion to single-quantum coherences. As a result, several conventions for labeling the Fl dimension of a 2D MQ-MAS spectrum appear in the literature. The corresponding relations for extracting the isotropic chemical shift, the quadrupole coupling constant, and the asymmetry parameter from experimental data are not always provided.