Static field gradient NMR studies of water diffusion in mesoporous silica

2020 ◽  
Vol 22 (25) ◽  
pp. 13989-13998 ◽  
Author(s):  
Max Weigler ◽  
Edda Winter ◽  
Benjamin Kresse ◽  
Martin Brodrecht ◽  
Gerd Buntkowsky ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Field Gradient ◽  
Pore Diameter ◽  
Static Field ◽  
Water Diffusion ◽  
Arrhenius Behavior ◽  
Nmr Studies

Water diffusion inside silica pores shows Arrhenius behavior and slows down when the pore diameter decreases or internal ice forms.

scholarly journals A single-shot measurement of time-dependent diffusion over sub-millisecond timescales using static field gradient NMR

2021 ◽  
Vol 154 (11) ◽  
pp. 111105
Author(s):  
Teddy X. Cai ◽  
Nathan H. Williamson ◽  
Velencia J. Witherspoon ◽  
Rea Ravin ◽  
Peter J. Basser
Keyword(s):  
Field Gradient ◽  
Static Field ◽  
Time Dependent ◽  
Single Shot

Lithium-ion diffusivity in complex hydrides: Pulsed-field-gradient NMR studies of LiLa(BH4)3Cl, Li3(NH2)2I and Li-1-CB9H10

2021 ◽  
Vol 362 ◽  
pp. 115585
Author(s):  
A.V. Skripov ◽  
G. Majer ◽  
O.A. Babanova ◽  
R.V. Skoryunov ◽  
A.V. Soloninin ◽  
...  
Keyword(s):  
Field Gradient ◽  
Lithium Ion ◽  
Nmr Studies ◽  
Pulsed Field Gradient Nmr ◽  
Pulsed Field ◽  
Complex Hydrides

Solid-state NMR studies of non-ionic surfactants confined in mesoporous silica

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Gerd Buntkowsky ◽  
Sonja Döller ◽  
Nadia Haro-Mares ◽  
Torsten Gutmann ◽  
Markus Hoffmann
Keyword(s):  
Solid State ◽  
Mesoporous Silica ◽  
Solid State Nmr ◽  
Role Models ◽  
Nmr Studies ◽  
Guest Molecules ◽  
Host Interactions ◽  
Functionalized Mesoporous Silica ◽  
Current Trends ◽  
Silica Materials

Abstract This review gives an overview of current trends in the investigation of confined molecules such as higher alcohols, ethylene glycol and polyethylene glycol as guest molecules in neat and functionalized mesoporous silica materials. All these molecules have both hydrophobic and hydrophilic parts. They are characteristic role-models for the investigation of confined surfactants. Their properties are studied by a combination of solid-state NMR and relaxometry with other physicochemical techniques and molecular dynamics techniques. It is shown that this combination delivers unique insights into the structure, arrangement, dynamical properties and the guest-host interactions inside the confinement.

Engineering Modified Mesoporous Silica Catalysts through Porosity and Surface Acidity Control for Selective Production of DME

2021 ◽  
Vol 894 ◽  
pp. 45-49
Author(s):  
Rosanna Viscardi ◽  
Vincenzo Barbarossa ◽  
Raimondo Maggi ◽  
Francesco Pancrazzi
Keyword(s):  
Mesoporous Silica ◽  
Dimethyl Ether ◽  
Sulfonic Acid ◽  
Pore Diameter ◽  
Solid Acid ◽  
Surface Acidity ◽  
High Surface ◽  
High Surface Area ◽  
Bifunctional Catalysts ◽  
Scanning Electronic Microscopy

DME has been received the attention as a renewable energy due to its thermal efficiencies equivalent to diesel fuel, lower NOx emission, near-zero smoke and non-toxic. DME can be obtained by methanol dehydration over solid acid catalysts or directly from syngas over bifunctional catalysts. The catalytic dehydration of methanol to DME has been widely studied in the literature over pure or modified γ -aluminas (γ-Al2O3) and zeolites. Mesoporous silica has obtained much consideration due to its well-defined structural order, high surface area, and tunable pore diameter. In this work, sulfonic acid and aluminium modified mesoporous silica were synthesized and tested as catalysts for production of dimethyl ether from methanol. The modified silicas were studied utilizing XRD, N2 physisorption, pyridine adsorption, and scanning electronic microscopy. The effects of reaction temperature and water deactivation on the methanol selectivity and conversion to dimethyl ether were investigated. Sulfonic acid modified mesoporous silica showed higher selectivity and stability of DME than that of aluminosilicate. The grafting of mesoporous silica with sulfonic groups displayed much more enhanced hydrothermal stability than Al-MCM-41 and γ-Al2O3.

Effects of cholesterol on transmembrane water diffusion in human erythrocytes measured using pulsed field gradient NMR

1995 ◽  
Vol 55 (3) ◽  
pp. 197-208 ◽  
Author(s):  
A. Reginald Waldeck ◽  
M. Hossein Nouri-Sorkhabi ◽  
David R. Sullivan ◽  
Philip W. Kuchel
Keyword(s):  
Field Gradient ◽  
Water Diffusion ◽  
Human Erythrocytes ◽  
Pulsed Field Gradient Nmr ◽  
Pulsed Field

NMR studies of water diffusion and relaxation in hydrating slag-based construction materials

2001 ◽  
Vol 19 (3-4) ◽  
pp. 547-548 ◽  
Author(s):  
Nikolaus Nestle ◽  
Petrik Galvosas ◽  
Oliver Geier ◽  
Marwan Dakkouri ◽  
Christian Zimmermann ◽  
...  
Keyword(s):  
Construction Materials ◽  
Water Diffusion ◽  
Nmr Studies

scholarly journals 2H NMR Studies on Water Dynamics in Functionalized Mesoporous Silica

2018 ◽  
Vol 232 (7-8) ◽  
pp. 1041-1058 ◽  
Author(s):  
Max Weigler ◽  
Martin Brodrecht ◽  
Hergen Breitzke ◽  
Felix Dietrich ◽  
Matthias Sattig ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Temperature Dependence ◽  
Liquid Water ◽  
Water Dynamics ◽  
Spin Lattice Relaxation ◽  
Nmr Studies ◽  
Solid Water ◽  
Water Species ◽  
Mcm 41 ◽  
Dynamic Crossover

AbstractMesoporous silica MCM-41 is prepared, for which the inner surfaces are modified by 3-(aminopropyl)triethoxysilane (APTES) in a controlled manner. Nitrogen gas adsorpition yields a pore diameter of 2.2 nm for the APTES functionalized MCM-41.2H nuclear magnetic resonance (NMR) and broadband dielectric spectroscopy (BDS) provide detailed and consistent insights into the temperature-dependent reorientation dynamics of water in this confinement. We find that a liquid water species becomes accompanied by a solid water species when cooling through ~210 K, as indicated by an onset of bimodal2H spin-lattice relaxation. The reorientation of the liquid water species is governed by pronounced dynamical heterogeneity in the whole temperature range. Its temperature dependence shows a mild dynamic crossover when the solid water species emerges and, hence, the volume accessible to the liquid water species further shrinks. Therefore, we attribute this variation in the temperature dependence to a change from bulk-like behavior towards interface-dominated dynamics. Below this dynamic crossover,2H line-shape and stimulted-echo studies show that water reorientation becomes anisotropic upon cooling, suggesting that these NMR approaches, but also BDS measurements do no longer probe the structural (α) relaxation, but rather a secondary (β) relaxation of water at sufficiently low temperatures. Then, another dynamic crossover at ~180 K can be rationalized in terms of a change of the temperature dependence of theβrelaxation in response to a glassy freezing of theαrelaxation of confined water. Comparing these results for APTES modied MCM-41 with previous findings for mesoporous silica with various pore diameters, we obtain valuable information about the dependence of water dynamics in restricted geometries on the size of the nanoscopic confinements and the properties of the inner surfaces.

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