Pore size distribution in mesoporous materials as studied by 1H NMR

Aksnes, Dagfinn W.; Førland, K.; Kimtys, L.

doi:10.1039/b103228n

Cited by 81 publications

(60 citation statements)

References 10 publications

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“…It was suggested by Stapf and Kimmich (Stapf and Kimmich, 1995) that the surface layer may interfere with the method of NMR cryoporometry by providing signal down to very low temperatures, thus being misinterpreted as indicating the presence of very small pores (Aksnes et al, 2001). …”

Section: Calibrationmentioning

confidence: 99%

Nuclear magnetic resonance cryoporometry

2008

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Nuclear Magnetic Resonance (NMR) cryoporometry is a technique for non-destructively determining pore size distributions in porous media through the observation of the depressed melting point of a confined liquid. It is suitable for measuring pore diameters in the range 2 nm -1 µm, depending on the absorbate. Whilst NMR cryoporometry is a pertabative measurement, the results are independent of spin interactions at the pore surface and so can offer direct measurements of pore volume as a function of pore diameter. Pore size distributions obtained with NMR cryoporometry have been shown to compare favourably with those from other methods such as gas adsorption, DSC thermoporosimetry, and SANS. The applications of NMR cryoporometry include studies of silica gels, bones, cements, rocks and many other porous materials. It is also possible to adapt the basic experiment to provide structural resolution in spatially dependent pore size distributions, or behavioural information about the confined liquid.

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Section: Calibrationmentioning

confidence: 99%

Nuclear magnetic resonance cryoporometry

2008

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“…where T m and T m0 are the melting temperatures of confined and bulk water, respectively, and k = 32.33 K nm [160]. The k value depends on the nature of the materials by analogy to NMR cryoporometry [54,55].…”

Section: Thermogravimetry Dsc and Thermoporometrymentioning

confidence: 99%

“…For simplicity, T m0 = 0 o C can be used here. The equation constants were determined for the DSC melting thermograms of bound water [160]. The differential pore size distribution dV/dR can be calculated from the DSC melting thermograms using equation [161-163]…”

Section: Thermogravimetry Dsc and Thermoporometrymentioning

confidence: 99%

Cryogels: Morphological, structural and adsorption characterisation

Gun'ko

Savina

Mikhalovsky

2013

Advances in Colloid and Interface Science

286

205

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*Graphical Abstract (for review)Cryotripic gelation technique allows the synthesis of solid and soft macroporous gels Textural characterisation of cryogel in native superhydrated state with noninvasive methods Adsorption and diffusion characteristics of macroporous cryogels with respect to macromolecules and cells Theoretical modelling of adsorption from aqueous media *Highlights (for review) Please find the revised manuscript entitled "Cryogels: morphological, structural and adsorption characterisation" by Vladimir M. Gun'ko, Irina N. Savina, Sergey V. Mikhalovsky to re-consider for publication in the "Advances in Colloid and Interface Science"The paper was completely edited and changed according to reviewers comments.Sincerely yours, Prof. V. M. Gun'koCover Letter ABSTRACTExperimental results on polymer, protein, and composite cryogels and data treatment methods used for morphological, textural, structural, adsorption and diffusion characterisation of the materials are analysed and compared. Treatment of microscopic images with specific software gives quantitative structural information on both native cryogels and freeze-dried materials that is useful to analyse the drying effects on their structure. A combination of cryoporometry, relaxometry, thermoporometry, small angle X-ray scattering (SAXS), equilibrium and kinetic adsorption of low and high-molecular weight compounds, diffusion breakthrough of macromolecules within macroporous cryogel membranes, studying interactions of cells with cryogels provides a consistent and comprehensive picture of textural, structural and adsorption properties of a variety of cryogels. This analysis allows us to establish certain regularities in the cryogel properties related to narrow (diameter 0.4 < d < 2 nm), middle (2 < d < 50 nm) and broad (50 < d < 100 nm) nanopores, micropores (100 nm < d < 100 m) and macropores (d > 100 m) with boundary sizes within modified life science pore classification. Particular attention is paid to water bound in cryogels in native superhydrated or freeze-dried states. At least, five states of water -free unbound, weakly bound (changes in the Gibbs free energy G < 0.5-0.8 kJ/mol) and strongly bound (G > 0.8 kJ/mol), and weakly associated (chemical shift of the proton resonance  H = 1-2 ppm) and strongly associated ( H = 3-6 ppm) waters can be distinguished in hydrated cryogels using 1 H NMR, DSC, TSDC, TG and other methods. Different software for image treatment or developed to analyse the data obtained with the adsorption, diffusion, SAXS, cryoporometry and thermoporometry methods and based on regularisation algorithms is analysed and used for the quantitative morphological, structural and adsorption characterisation of individual and composite cryogels, including polymers filled with solid nano-or microparticles.

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“…Freezing of bound water occurs at low temperatures at T < 260 K (Figs. 7a and 8) because of the freezing point depression for liquids confined in pores [16,17,[19][20][21][22]. Since freezing of bound water occurs at T < 260 K, all of this water can be assigned to strongly bound water (SBW).…”

Section: Interfacial Behavior Of Adsorbates Bound To Cryosilicasmentioning

confidence: 99%

“…The freezing point depression for water in narrow pores is described by the GibbsThomson relation (assuming a cylindrical pore shape) at radius R [17,[19][20][21][22] given as Eq. (3);…”

Section: H Nmr Spectroscopymentioning

confidence: 99%

High-pressure cryogelation of nanosilica and surface properties of cryosilicas

Gun’ko

Туров

Zarko

et al. 2013

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Gun'ko, V M.; Turov, V V.; Zarko, V I.; Prykhod'ko, G P.; Remez, O S.; Leboda, R; Skubiszewska-Zieba, J; Pahklov, E M.; and Blitz, Jonathan, "High-pressure cryogelation of nanosilica and surface properties of cryosilicas" (2013 AbstractSilica cryogels (cryosilicas) in a powder state were synthesized with different concentrations of fumed silica A-300 (C A-300 = 5-20 wt.%), sonicated in aqueous suspension, then frozen at 14 o C at different pressures in a high-pressure stainless steel reactor (a freezing bomb), and dried in air at room temperature. To analyze the effects of low temperature and high pressure, samples were also prepared at 14 o C or room temperature and standard pressure. The structural and adsorption properties of the powder materials were studied using nitrogen adsorption, highresolution transmission electron microscopy, infrared spectroscopy, thermogravimetry, lowtemperature 1 H NMR spectroscopy and thermally stimulated depolarization current. The structural, textural, adsorption and relaxation characteristics of high-pressure cryogel hydrogels and related dried powders are strongly dependent on the silica content in aqueous suspensions frozen at 1, 450 or 1000 atmospheres and then dried. The largest changes are found with C A-300 = 20 wt.% which are analyzed with respect to the interfacial behavior of nonpolar, weakly polar and polar adsorbates using low temperature 1 H NMR spectroscopy.

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Pore size distribution in mesoporous materials as studied by 1H NMR

Cited by 81 publications

References 10 publications

Nuclear magnetic resonance cryoporometry

Nuclear magnetic resonance cryoporometry

Cryogels: Morphological, structural and adsorption characterisation

High-pressure cryogelation of nanosilica and surface properties of cryosilicas

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