Layer analysis of the structure of water confined in vycor glass

Gallo, Paola; Ricci, Maria Antonietta; Rovere, Mauro

doi:10.1063/1.1423662

Cited by 151 publications

(174 citation statements)

References 30 publications

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“…It is generally believed that near the hydrophilic surface such as silica there is a 2-to 3-Å layer of water with about 10% higher density, whereas in the center of the pores water distributes uniformly (32,(55)(56)(57)(58)(59)(60)(61). When we compare the normalized particle structure factors of this core-shell cylinder and its average, we find that at around the Bragg peak position (Q ¼ 0.2 Å −1 ), the difference of thePðQÞ is about 5%.…”

Section: Methodsmentioning

confidence: 99%

“…That is, the hydrophilic silanol surface provides a small and constant perturbation to the confined water. It is known that near the hydrophilic surface such as silica, there is a layer of denser water, whereas in the center of the pores water distributes uniformly (32,(55)(56)(57)(58)(59)(60)(61). The behavior of water near a hydrophobic surface may be different because of the lack of compensating hydrogen bonds from the surface and therefore requires more careful investigations (10,(58)(59)(60)62).…”

Section: Methodsmentioning

confidence: 99%

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Density hysteresis of heavy water confined in a nanoporous silica matrix

Zhang

Faraone

Kamitakahara

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

109

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A neutron scattering technique was developed to measure the density of heavy water confined in a nanoporous silica matrix in a temperature-pressure range, from 300 to 130 K and from 1 to 2,900 bars, where bulk water will crystalize. We observed a prominent hysteresis phenomenon in the measured density profiles between warming and cooling scans above 1,000 bars. We interpret this hysteresis phenomenon as support (although not a proof) of the hypothetical existence of a first-order liquid-liquid phase transition of water that would exist in the macroscopic system if crystallization could be avoided in the relevant phase region. Moreover, the density data we obtained for the confined heavy water under these conditions are valuable to large communities in biology and earth and planetary sciences interested in phenomena in which nanometer-sized water layers are involved.confined water | equation of state | liquid-liquid critical phenomenon I n many biological and geological systems, water resides in pores of nanoscopic dimensions, or close to hydrophilic or hydrophobic surfaces, comprising a layer of water, one or two molecules thick, with properties often different from the bulk. Such "confined" or "interfacial" water has attracted considerable attention, due to its fundamental importance in many processes, such as protein folding, concrete curing, corrosion, molecular and ionic transport, etc. (1-3). However, our understanding of the numerous physicochemical anomalies of confined water, and indeed of bulk water, is still incomplete. Basic gaps persist, among which the most interesting one is the origin of the unusual behavior of water in the supercooled region where water remains in the liquid state below the melting point (4-7). Recent studies have aimed at explaining anomalies such as the density maximum and minimum (8-10), and the apparent divergence of the thermodynamic response functions at 228 K at ambient pressure (11). The three major hypothesized scenarios currently under scrutiny are the "singularity-free (SF) scenario" (12, 13), the "liquidliquid critical point (LLCP) scenario" (14, 15), and the "critical point-free (CPF) scenario" (16). It is hypothesized, by all these three scenarios, that in the low temperature range bulk water is composed of a mixture of two structurally distinct liquids: the low-density liquid (LDL) and the high-density liquid (HDL). They are respectively the thermodynamic continuation of the low-density amorphous ice (LDA) and high-density amorphous ice (HDA) into the liquid state. Evidence of a first-order phase transition between LDA and HDA has been reported since 1985 (17-20). Subsequently, several experimental findings have been interpreted as support of the hypothetical existence of two different structural motifs of liquid water (21-27). However, some of the interpretations have been questioned (28,29). So far, direct evidence of a first-order liquid-liquid phase transition between LDL and HDL, as a thermodynamic extension of the first-order transition established in the am...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Density hysteresis of heavy water confined in a nanoporous silica matrix

Zhang

Faraone

Kamitakahara

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

109

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“…However, atomistic simulations of some of these specific systems [e.g., water in silica pores [50]] do not seem to produce this effect.…”

Section: A Proton Probability Densitymentioning

confidence: 99%

Effect of quantum nuclear motion on hydrogen bonding

McKenzie

Bekker

Athokpam

et al. 2014

The Journal of Chemical Physics

160

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This work considers how the properties of hydrogen bonded complexes, X-H· · · Y, are modified by the quantum motion of the shared proton. Using a simple two-diabatic state model Hamiltonian, the analysis of the symmetric case, where the donor (X) and acceptor (Y) have the same proton affinity, is carried out. For quantitative comparisons, a parametrization specific to the O-H· · · O complexes is used. The vibrational energy levels of the one-dimensional ground state adiabatic potential of the model are used to make quantitative comparisons with a vast body of condensed phase data, spanning a donor-acceptor separation (R) range of about 2.4 − 3.0Å, i.e., from strong to weak hydrogen bonds. The position of the proton (which determines the X-H bond length) and its longitudinal vibrational frequency, along with the isotope effects in both are described quantitatively. An analysis of the secondary geometric isotope effect, using a simple extension of the two-state model, yields an improved agreement of the predicted variation with R of frequency isotope effects. The role of bending modes is also considered: their quantum effects compete with those of the stretching mode for weak to moderate Hbond strengths. In spite of the economy in the parametrization of the model used, it offers key insights into the defining features of H-bonds, and semi-quantitatively captures several trends.

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“…5 Interesting phenomena arising in confined water have been observed experimentally, as well as in theoretical and computational studies. [6][7][8][9][10][11] These include drastically different local structure and dynamics 12,13 and the appearance of phase transitions not observable in the bulk under the same thermodynamic conditions. 14 Such behavior arises from the subtle interplay of the fluid correlation and confinement geometric length scales 15 and the nature of the interactions between water and the confining medium.…”

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confidence: 99%

Evolution from Surface-Influenced to Bulk-Like Dynamics in Nanoscopically Confined Water

et al. 2009

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We use molecular dynamics simulations to study the influence of confinement on the dynamics of a nanoscopic water film at T ) 300 K and F ) 1.0 g cm -3. We consider two infinite hydrophilic ( -cristobalite) silica surfaces separated by distances between 0.6 and 5.0 nm. The width of the region characterized by surfacedominated slowing down of water rotational dynamics is ∼0.5 nm, while the corresponding width for translational dynamics is ∼1.0 nm. The different extent of perturbation undergone by the in-plane dynamic properties is evidence of rotational-translational decoupling. The local in-plane rotational relaxation time and translational diffusion coefficient collapse onto confinement-independent "master" profiles as long as the separation d g 1.0 nm. Long-time tails in the perpendicular component of the dipole moment autocorrelation function are indicative of anisotropic behavior in the rotational relaxation.The properties of water confined in nanoscale geometries are of considerable scientific and technological interest. Nanoconfined water constitutes much of the environment in the cytoplasm of cells, where it acts as an active regulator of biological functions including protein folding.1 Understanding the transport and thermodynamic properties of water in molecular-scale geometries is key in a wide array of fields, from nanoand microfluidics, 2 to cloud seeding in the atmosphere, 3 corrosion inhibition, 4 and heterogeneous catalysis. 5 Interesting phenomena arising in confined water have been observed experimentally, as well as in theoretical and computational studies. [6][7][8][9][10][11] These include drastically different local structure and dynamics 12,13 and the appearance of phase transitions not observable in the bulk under the same thermodynamic conditions. 14 Such behavior arises from the subtle interplay of the fluid correlation and confinement geometric length scales 15 and the nature of the interactions between water and the confining medium.Recent experimental studies (e.g., see ref 16) have exploited the confinement of water in nanoscale geometries in order to investigate the possible existence of a liquid-liquid phase transition, terminating at a second critical point in supercooled water. Liquid-liquid coexistence has been postulated to occur in the deeply supercooled region of the phase diagram of water, at temperatures below the onset of homogeneous crystallization (∼231 K at 1 bar).17 By confining water in silica nanopores of 1.4-2.4 nm in diameter, Chen and co-workers were able to inhibit crystal nucleation and thereby study liquid water at temperatures down to 160 K (e.g., see refs 16, 18-22). Thus, confinement allows the study of a system under conditions that are inaccessible in the bulk. Because confining surfaces inevitably modify the structure and dynamics of proximal water, it is important to develop a fundamental understanding of the spatial range of such perturbations and, more generally, of the relationship between experiments performed on a confined system and its bulk behavi...

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Layer analysis of the structure of water confined in vycor glass

Cited by 151 publications

References 30 publications

Density hysteresis of heavy water confined in a nanoporous silica matrix

Density hysteresis of heavy water confined in a nanoporous silica matrix

Effect of quantum nuclear motion on hydrogen bonding

Evolution from Surface-Influenced to Bulk-Like Dynamics in Nanoscopically Confined Water

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