Thermal Expansion of Confined Water

Xu, Shuangyan; Scherer, George W.; Mahadevan, Thiruvilla S.; Garofalini, Stephen H.

doi:10.1021/la804061p

Cited by 69 publications

(69 citation statements)

References 45 publications

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“…He and his students developed a new interatomic potential that proved to be the more accurate than any previously reported for simulating the properties of water [25]. The MD simulations were found to be in quantitative agreement with our experimental results for the expansion of water in small pores [26,27]. The simulations also confirmed the existence of a region of low mobility for water within ~0.6 nm of the surface of silica [28] that quantitatively accounted for our measurements of permeability and diffusivity in porous glasses.…”

supporting

confidence: 78%

Mechanical Properties of Gels; Stress from Confined Fluids

Scherer¹

2009

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Unexpended funds: NoneThis program began under the title of "Mechanical Properties of Gels", with the goal of understanding how the elastic modulus of a gel is controlled by its structure. Our early focus was on characterization of the elastic properties of the network, including the elastic efficiency (or, load-bearing fraction) of the network [1,2]. We also studied methods for characterization of the network, including development of a new model for adsorption on networks [3,4,5] that was used to follow the evolution of microstructure during sintering [6,7]. We proved that aerogels contract severely during nitrogen condensation in a standard adsorption experiment [8,9,10] and showed how the (erroneous) measured size distribution could be corrected [11]. The phenomenon of shrinkage during adsorption has recently attracted considerable interest, as indicated by the dedication of an entire session to it at a recent conference [12]. We also developed a novel method for measuring the gas permeability of aerogels over a wide range of pressure [13].The next few years were devoted to an extremely fruitful program of computer simulation in which we developed a new algorithm for simulating growth of clusters, allowing for flexibility in the branches [14]. This model, developed by Hang-Shing Ma in collaboration

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supporting

confidence: 78%

Mechanical Properties of Gels; Stress from Confined Fluids

Scherer¹

2009

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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: 86%

“…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%

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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“…First, the thermal expansion coefficient βðTÞ depends on the temperature rise T above the equilibrium temperature. 20,21 In thermal confinement, T is proportional to the optical energy deposition. When T is small, βðTÞ ≈ β 1 þ β 2 T, where β 1 and β 2 are the first two coefficients in the Taylor expansion around the equilibrium temperature.…”

Section: Principles Of Pa Nanoscopymentioning

confidence: 99%

“…When T is small, βðTÞ ≈ β 1 þ β 2 T, where β 1 and β 2 are the first two coefficients in the Taylor expansion around the equilibrium temperature. 20 In water and soft tissues at room temperature, 21 β 2 ≈ 0.04β 1 , and, therefore, a temperature rise of 3 K can change the thermal expansion coefficient by >10%.…”

Section: Principles Of Pa Nanoscopymentioning

confidence: 99%

Label-free photoacoustic nanoscopy

et al. 2014

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Abstract. Super-resolution microscopy techniques-capable of overcoming the diffraction limit of light-have opened new opportunities to explore subcellular structures and dynamics not resolvable in conventional far-field microscopy. However, relying on staining with exogenous fluorescent markers, these techniques can sometimes introduce undesired artifacts to the image, mainly due to large tagging agent sizes and insufficient or variable labeling densities. By contrast, the use of endogenous pigments allows imaging of the intrinsic structures of biological samples with unaltered molecular constituents. Here, we report label-free photoacoustic (PA) nanoscopy, which is exquisitely sensitive to optical absorption, with an 88 nm resolution. At each scanning position, multiple PA signals are successively excited with increasing laser pulse energy. Because of optical saturation or nonlinear thermal expansion, the PA amplitude depends on the nonlinear incident optical fluence. The high-order dependence, quantified by polynomial fitting, provides super-resolution imaging with optical sectioning. PA nanoscopy is capable of super-resolution imaging of either fluorescent or nonfluorescent molecules. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Thermal Expansion of Confined Water

Cited by 69 publications

References 45 publications

Mechanical Properties of Gels; Stress from Confined Fluids

Mechanical Properties of Gels; Stress from Confined Fluids

Density hysteresis of heavy water confined in a nanoporous silica matrix

Label-free photoacoustic nanoscopy

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