Structural Correlations in Liquid Water:  A New Interpretation of IR Spectroscopy

Schmidt, Diedrich A.; Miki, Kazushi

doi:10.1021/jp074737n

Cited by 119 publications

(117 citation statements)

References 53 publications

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“…8 has been decomposed into the four contributions labelled as I i (i = 1, 4) corresponding to the different populations of OH oscillators present in the system. [50][51][52] As shown in previous studies, [36][37][38]40 the sums of the percentage intensities of the two sub-bands found, respectively, at the lowest and highest wavenumbers, i.e. (I 1 + I 2 ) and (I 3 + I 4 ) in Fig.…”

Section: Restructuring Of the Hb Network Of Confined Watersupporting

confidence: 79%

Toward an understanding of the thermosensitive behaviour of pH-responsive hydrogels based on cyclodextrins

et al. 2015

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The molecular mechanism responsible for the thermosensitive behaviour exhibited by pH-responsive cyclodextrin-based hydrogels is explored here with the twofold aim of clarifying some basic aspects of H-bond interactions in hydrogel phases and contributing to a future engineering of cyclodextrin hydrogels for targeted delivery and release of bioactive agents. The degree of H-bond association of water molecules entrapped in the gel network and the extent of intermolecular interactions involving the hydrophobic/ hydrophilic moieties of the polymer matrix are probed by UV Raman and IR experiments, in order to address the question of how these different and complementary aspects combine to determine the pH-dependent thermal activation exhibited by these hydrogels. Complementary vibrational spectroscopies are conveniently employed in this study with the aim of safely disentangling the spectral response arising from the two main components of the hydrogel systems, i.e. the polymer matrix and water solvent. The experimental evidence suggests that the dominant effects in the mechanism of solvation of cyclodextrin-based hydrogels are due to the changes occurring, upon increasing of temperature, in the hydrophobicity character of specific chemical moieties of the polymer, as triggered by pH variations. The achievements of this work corroborate the potentiality of the UV Raman scattering technique, in combination with more conventional IR experiments, to provide a ''molecular view'' of complex macroscopic phenomena exhibited in hydrogel phases.

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Section: Restructuring Of the Hb Network Of Confined Watersupporting

confidence: 79%

Toward an understanding of the thermosensitive behaviour of pH-responsive hydrogels based on cyclodextrins

et al. 2015

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“…For water, four-body and higher order interactions seem to be negligible with respect to the three-body term (28,29). Hence, the fourth component to the interaction potential is the many-body effect due to H-bonds (30)(31)(32), that minimizes the energy when the H-bonds of nearby molecules assume a tetrahedral orientation. This is accomplished by further adding to the Hamiltonian in Eqs.…”

Section: Cooperative Cell Model Of Watermentioning

confidence: 99%

Effect of hydrogen bond cooperativity on the behavior of water

Stokely

Mazza

Stanley

et al. 2010

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

262

250

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Four scenarios have been proposed for the low-temperature phase behavior of liquid water, each predicting different thermodynamics. The physical mechanism that leads to each is debated. Moreover, it is still unclear which of the scenarios best describes water, because there is no definitive experimental test. Here we address both open issues within the framework of a microscopic cell model by performing a study combining mean-field calculations and Monte Carlo simulations. We show that a common physical mechanism underlies each of the four scenarios, and that two key physical quantities determine which of the four scenarios describes water: (i) the strength of the directional component of the hydrogen bond and (ii) the strength of the cooperative component of the hydrogen bond. The four scenarios may be mapped in the space of these two quantities. We argue that our conclusions are model independent. Using estimates from experimental data for H-bond properties the model predicts that the low-temperature phase diagram of water exhibits a liquid-liquid critical point at positive pressure.anomalous liquids | liquid-liquid transition | liquid water | mean field | Monte Carlo simulations W ater's phase diagram is rich and complex: more than sixteen crystalline phases (1), and two or more glasses (2-4) have been reported. The liquid state also displays interesting behavior, such as the density maximum for 1 atm at 4°C. The volume fluctuations hðδV Þ 2 i, entropy fluctuations hðδSÞ 2 i, and cross fluctuations between volume and entropy hδV δSi, proportional to the magnitude of isothermal compressibility K T , isobaric specific heat C P , and isobaric thermal expansivity α P , respectively, show anomalous increases in magnitude upon cooling (5). Further, these quantities display an apparent divergence for 1 atm at −45°C (2), hinting at interesting phase behavior in the supercooled region.Microscopically, liquid water's anomalous behavior is understood as resulting from the tendency of neighboring molecules to form hydrogen (H) bonds upon cooling with a decrease of local potential energy, decrease of local entropy, and increase of local volume due to the formation of local open structures of bonded molecules. Different models include these H-bond features, but depending on the assumptions and approximations of each model, different conclusions are obtained for the low-T phase behavior. The relevant region of the bulk-liquid state cannot be probed experimentally, and none of the theories tested because crystallization of bulk water is unavoidable below the homogeneous nucleation temperature T H (−38°C at 1 atm). Four Scenarios for Supercooled WaterDue to the difficulty of obtaining experimental evidence, theoretical and numerical analyses are useful. Four separate scenarios for the pressure-temperature (P-T) phase diagram have been proposed: (I) The stability limit (SL) scenario (6) hypothesizes that the superheated liquid-gas spinodal at negative pressure reenters the positive P region below T H ðPÞ. In this view, the liq...

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“…Care must be taken when using deconvolution algorithms and the resulting interpretation, and we previously discussed our deconvolution method in detail. [21] Indeed, we examined the deconvolution as a function of peak shape and the number of components in the n(OH) band and found that the best fit, which minimized both c 2 and the sum of the fit residual, corresponds to six Gaussian peaks. Fitting with Lorentzian line shapes was also explored, but all such fits produced larger errors for both c 2 and the sum of the fit residual and could not reproduce the overall envelope of the n(OH) curve.…”

Section: Deconvolutionmentioning

confidence: 99%

“…[2,3,[14][15][16] Although the OH stretching band [n(OH) band] originates from OÀH vibrations, it is also correlated to the overall structure of water, [6,17,18] because the surrounding H-bonds alter the intermolecular bond and thus change the dipole moment and vibrational spectra. [1,[18][19][20][21] The structure of the n(OH) band can therefore provide information on how the H-bond network is modified by defects. Here we investigate how low-concentration ionic defects modify the H-bond network topology by examining changes in the n(OH) band.…”

Section: Introductionmentioning

confidence: 99%

Defective Continuous Hydrogen‐Bond Networks: An Alternative Interpretation of IR Spectroscopy

Schmidt

Miki

2008

ChemPhysChem

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We apply our previously developed deconvolution method and interpretation to analyze changes in the OH stretching band [nu(OH) band] of low-concentration (< or =0.2 m) aqueous solutions of NaCl and KCl. We treat these simple, monovalent ions as defects in the hydrogen-bond network of pure water and quantify the changes in the spectra at low defect concentration with an "order parameter". Order-parameter analysis of difference spectra of the two solutions leads to hydration numbers of 7.0+/-1.0 and 5.9+/-0.3 for K(+) and Na(+), respectively. Additionally, we find that changes in the nu(OH) band due to low concentrations of ions result from changes in the topology of the hydrogen-bond network.

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Structural Correlations in Liquid Water: A New Interpretation of IR Spectroscopy

Cited by 119 publications

References 53 publications

Toward an understanding of the thermosensitive behaviour of pH-responsive hydrogels based on cyclodextrins

Toward an understanding of the thermosensitive behaviour of pH-responsive hydrogels based on cyclodextrins

Effect of hydrogen bond cooperativity on the behavior of water

Defective Continuous Hydrogen‐Bond Networks: An Alternative Interpretation of IR Spectroscopy

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