Vibrational Dynamics of Water within Mesoporous Materials at Different Hydration Levels during Adsorption and Desorption Processes

Huang, Xiaohong; Wang, Qiang; Liu, Xiao X.; Yang, Shu Ching; Li, Chen X.; Sun, Gang; Pan, Lei; Lü, Kun

doi:10.1021/jp9051566

Cited by 29 publications

(43 citation statements)

References 29 publications

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“…Simple estimates suggest that they would at best have a small effect on the spectra that would be difficult to discern in a fully hydrated pore such as that considered here. This is supported by experimental measurements 15,23,24 and the number densities (e.g., in the two pores considered here there are only 56 and 86 silanol groups compared to 882 and 818 water OH groups, respectively). However, the electric field exerted by the silanols on the OH groups is included in the determination of the water OH stretching frequencies, with the exception of the case described below where the field due to the entire silica pore is neglected.…”

Section: A Frequency Map and Implementationsupporting

confidence: 77%

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confidence: 99%

“…24,75,76 For example, Huang et al measured the Raman spectrum of H 2 O confined in 6.9 nm diameter Vycor glass and compared it to the bulk water spectrum. 24 They found that the key differences between bulk and confined water are a general blue-shifting of the spectrum along with the appearance of a shoulder on the high-frequency side. They also observed a decrease in the red-shifted shoulder around 3200 cm −1 that appears in the neat H 2 O spectrum, 77,78 but is absent in our simulated spectra for HOD/D 2 O.…”

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confidence: 99%

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Simulations of the infrared, Raman, and 2D-IR photon echo spectra of water in nanoscale silica pores

Burris

Laage

Thompson

2016

The Journal of Chemical Physics

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Vibrational spectroscopy is frequently used to characterize nanoconfined liquids and probe the effect of the confining framework on the liquid structure and dynamics relative to the corresponding bulk fluid. However, it is still unclear what molecular-level information can be obtained from such measurements. In this paper, we address this question by using molecular dynamics (MD) simulations to reproduce the linear infrared (IR), Raman, and two-dimensional IR (2D-IR) photon echo spectra for water confined within hydrophilic (hydroxyl-terminated) silica mesopores. To simplify the spectra the OH stretching region of isotopically dilute HOD in D 2 O is considered. An empirical mapping approach is used to obtain the OH vibrational frequencies, transition dipoles, and transition polarizabilities from the MD simulations. The simulated linear IR and Raman spectra are in good general agreement with measured spectra of water in mesoporous silica reported in the literature. The key effect of confinement on the water spectrum is a vibrational blueshift for OH groups that are closest to the pore interface. The blueshift can be attributed to the weaker hydrogen bonds (H-bonds) formed between the OH groups and silica oxygen acceptors. Non-Condon effects greatly diminish the contribution of these OH moieties to the linear IR spectrum, but these weaker H-bonds are readily apparent in the Raman spectrum. The 2D-IR spectra have not yet been measured and thus the present results represent a prediction. The simulated spectra indicates that it should be possible to probe the slower spectral diffusion of confined water compared to the bulk liquid by analysis of the 2D-IR spectra. Published by AIP Publishing. [http://dx

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Section: A Frequency Map and Implementationsupporting

confidence: 77%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Simulations of the infrared, Raman, and 2D-IR photon echo spectra of water in nanoscale silica pores

Burris

Laage

Thompson

2016

The Journal of Chemical Physics

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“…In order to completely remove the organic pollutants inside the pores, the glass disks were pretreated strictly following the procedure described in Ref. 19. Bulk aqueous solutions of CuBr 2 were obtained by dissolving an appropriate amount of CuBr 2 salt (Sigma, 99.99 wt.%) into de-ionized water.…”

Section: A Sample Preparationmentioning

confidence: 99%

Coordination variation of hydrated Cu2+/Br1− ions traversing the interfacial water in mesopores

Wang

Huang

et al. 2012

AIP Advances

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Resolution of the atomistic and electronic details about the coordination structure variation of hydrated ions in the interfacial water is still a tough challenge, which is, however, essentially important for the understanding of ion adsorption, permeation and other similar processes in aqueous solutions. Here we report the tracing of coordination structure variation for hydrated Cu2+/Br1- ions traversing the interfacial water in Vycor mesopores (ϕ = 7.6 nm) by employing both X-ray absorption near edge structure and extended X-ray absorption fine structure spectroscopies. By controlled desorption/adsorption of water, the filling fraction of the mesopores, thus the water layer thickness, can be adjusted, which in turn effects the variation of coordination structure of the ions therein. It is found that both Cu2+ and Br1- ions prefer staying exclusively in the core water, and in this circumstance no ion pairs have been detected in the solution of concentrations up to 1.0 M. Following capillary decondensation occurring at a filling fraction of ∼35% which corresponds to a water layer of about three monolayers, Br1- ions begin immediately to reconstruct their first coordination shell, characterized by ionic dehydration, shrinkage of ion-water bond length, and formation of ion pairs. In contrast, Cu2+ ions can retain a bulk-like coordination structure till being driven to bond directly to the pore surface when the filling fraction is below 20%. At the final stage of dehydration via thermal vacuum treatment at 110°C, Cu2+ ions can be completely reduced to the Cu1+ state, and recover at room temperature only when the filling fraction is above 14%. These results may be inspirable for the investigation of similar problems concerning hydrated ions in water solution under different confining conditions.

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“…However, to date, there have been very few studies of probing connement of water with silica systems of tunable size. [8][9][10][11][12][13] The use of colloidal particles as hard templates is perhaps the oldest strategy for formation of hollow nanostructures and is still widely used today. An extensive amount of research has gone into the development of colloidal particles with the spec-ications needed to act as good templates.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of microporous silica nanoparticles to study water phase transitions by vibrational spectroscopy

et al. 2019

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Vibrational Dynamics of Water within Mesoporous Materials at Different Hydration Levels during Adsorption and Desorption Processes

Cited by 29 publications

References 29 publications

Simulations of the infrared, Raman, and 2D-IR photon echo spectra of water in nanoscale silica pores

Simulations of the infrared, Raman, and 2D-IR photon echo spectra of water in nanoscale silica pores

Coordination variation of hydrated Cu2+/Br1− ions traversing the interfacial water in mesopores

Synthesis of microporous silica nanoparticles to study water phase transitions by vibrational spectroscopy

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