Freezing Phenomena in Adsorbed Water as Studied by NMR

Overloop, K; Vangerven, L.

doi:10.1006/jmra.1993.1028

Cited by 186 publications

(89 citation statements)

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“…The anodization times were 30 min (PS-1) and 75 min (PS-2). For removing the PSi from the substrates, an electropolishing step with a current density of 500 mA/cm 2 was applied for 2-3 s. For the evaluation of the pore-size distribution function of the used PSi materials, NMR cryoporometry was used [17,18]. The experimental data (not shown) led to relatively narrow distributions with an average pore size of 9.6 and 3.5 nm for PS-1 and PS-2, respectively.…”

Section: Methodsmentioning

confidence: 99%

Concentration-dependent self-diffusion of adsorbates in mesoporous materials

Valiullin

Kortunov

Kärger

et al. 2005

Magnetic Resonance Imaging

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Section: Methodsmentioning

confidence: 99%

Concentration-dependent self-diffusion of adsorbates in mesoporous materials

Valiullin

Kortunov

Kärger

et al. 2005

Magnetic Resonance Imaging

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“…IR spectroscopy of water dynamics in nanometer-size reverse micelles show that approximately half of the water in a 4 nm diameter micelle is ''interfacial'' while the other half is bulk-like [26], implying a 5.6 Å interfacial layer thickness. NMR studies of water adsorbed to porous glass show that 2.5-3 monolayers are essentially in a ''frozen'' amorphous structure even at room temperature, and that this fraction remains amorphous as the sample is cooled to freezing temperatures [27]. Water confined inside the 2 nm pores of porous glass does not crystallize [28], and it crystallizes only very slowly in the 6.5 nm channels of certain protein crystals [29].…”

Section: Prl 110 015703 (2013) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

Critical Droplet Theory Explains the Glass Formability of Aqueous Solutions

2013

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When pure water is cooled at $10 6 K=s, it forms an amorphous solid (glass) instead of the more familiar crystalline phase. The presence of solutes can reduce this required (or ''critical'') cooling rate by orders of magnitude. Here, we present critical cooling rates for a variety of solutes as a function of concentration and a theoretical framework for understanding these rates. For all solutes tested, the critical cooling rate is an exponential function of concentration. The exponential's characteristic concentration for each solute correlates with the solute's Stokes radius. A modification of critical droplet theory relates the characteristic concentration to the solute radius and the critical nucleation radius of ice in pure water. This simple theory of ice nucleation and glass formability in aqueous solutions has consequences for general glass-forming systems, and in cryobiology, cloud physics, and climate modeling. DOI: 10.1103/PhysRevLett.110.015703 PACS numbers: 64.60.QÀ, 05.40.Àa, 64.70.dg Ice nucleation and growth are of major interest in fields ranging from cryobiology to atmospheric physics. Ice is a key issue in cryopreservation of cells and tissues [1] and in cryocooling of samples for macromolecular crystallography [2,3], where solutes like salts, sugars, alcohols, and polyols can have dramatic effects on ice formation. In atmospheric physics, models of cloud formation are sensitive to the nature of the critical nucleus of ice crystals [4] with implications for climate models [5]. Supercooled water is an interesting system in its own right [6], and the formation of crystalline phases from supercooled solutions is an active area of study [7].Previous experiments have focused on properties such as the melting and glass transition temperatures, and models to explain the data have largely been phenomenological. Similar models have been applied to explain glass formability in a wide variety ofnonaqueous systems. Here, we report measurements of the minimum cooling rates [or ''critical cooling rates'' (CCRs)] required to prevent ice formation in aqueous solutions during cooling to $100 K or below. We show that a surprisingly simple statistical modification to classical thermodynamic nucleation theory provides an excellent account of these data.We studied eight different solutes (see Fig. 1), including a salt (sodium chloride), simple alcohols (methanol, ethanol), sugars (dextrose, trehalose), polyols (glycerol, ethylene glycol), and polyethylene glycol 200 (PEG 200). All are compact and highly soluble and can have large effects on critical cooling rates required for vitrification.The effects of these solutes on ice nucleation were evaluated by measuring the critical cooling rate above which no ice was observed. Below the critical rate, a sample turns opaque on cooling, indicating the formation of polycrystalline ice. As the rate increases, a transition to transparent samples is observed. This optical transition corresponds to a transition in the x-ray diffraction patterns obtained from the cooled sam...

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“…Further studies of water in porous media revealed a hysteresis between the freezing (∆T f ) and melting (∆T m ) cycles of the confined liquid (Overloop and van Gerven, 1993). This hysteresis may be compared to the capillary condensation measured in gas adsorption (Beurroies et al, 2004).…”

Section: Thermodynamics: Application To Nmrmentioning

confidence: 99%

“…Overloop and van Gerven suggested that NMR was suitable for measuring gross pore volume, and for this application demonstrated the validity of the Kelvin Equation (although the Gibbs-Thomson form was quoted) (Overloop and van Gerven, 1993).…”

Section: Thermodynamics: Application To Nmrmentioning

confidence: 99%

“…Both NMR cryoporometry (Strange et al, 1993) and DSC thermoporosimetry rely on the Gibbs-Thomson equation concerning the relationship between the characteristic pore length scale and the change in the freezing point of the liquid, or melting point of its solid crystal, due to confinement within the porous matrix (see section 2). However, the freez-ing and melting behaviour of confined liquids / solids is often complex, with the thermodynamic properties of the confined material being modified from those of the bulk (Christenson, 2001;Overloop and van Gerven, 1993). NMR cryoporometry has an advantage over DSC thermoporosimetry in that DSC measures transient heat flows and thus has a minimum rate at which the measurement may be made.…”

Section: Introductionmentioning

confidence: 99%

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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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Freezing Phenomena in Adsorbed Water as Studied by NMR

Cited by 186 publications

References 0 publications

Concentration-dependent self-diffusion of adsorbates in mesoporous materials

Concentration-dependent self-diffusion of adsorbates in mesoporous materials

Critical Droplet Theory Explains the Glass Formability of Aqueous Solutions

Nuclear magnetic resonance cryoporometry

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