Phase separation of acetonitrile-water mixtures and minimizing of ice crystallites from there in confinement of MCM-41

Kittaka, Shigeharu; Kuranishi, Miki; Ishimaru, Shinji; Umahara, Osamu

doi:10.1063/1.2712432

Cited by 25 publications

(29 citation statements)

References 17 publications

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“…18 These effects may give rise to collective responses of the fluids -such as segregation phenomena, [19][20][21] modifications in phase diagrams, [22][23][24][25][26][27][28] and a) Author to whom correspondence should be addressed. Electronic mail: dhlaria@cnea.gov.ar.…”

Section: Introductionmentioning

confidence: 99%

Aqueous electrolytes confined within functionalized silica nanopores

Videla

Sala

Martı́

et al. 2011

The Journal of Chemical Physics

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Molecular dynamics simulations have been carried out to investigate structural and dynamical characteristics of NaCl aqueous solutions confined within silica nanopores in contact with a "bulk-like" reservoir. Two types of pores, with diameters intermediate between 20 Å and 37.5 Å, were investigated: The first one corresponded to hydrophobic cavities, in which the prevailing wall-solution interactions were of the Lennard-Jones type. In addition, we also examined the behavior of solutions trapped within hydrophilic cavities, in which a set of unsaturated O-sites at the wall were transformed in polar silanol Si-OH groups. In all cases, the overall concentrations of the trapped electrolytes exhibited important reductions that, in the case of the narrowest pores, attained 50% of the bulk value. Local concentrations within the pores also showed important fluctuations. In hydrophobic cavities, the close vicinity of the pore wall was coated exclusively by the solvent, whereas in hydrophilic pores, selective adsorption of Na + ions was also observed. Mass and charge transport were also investigated. Individual diffusion coefficients did not present large modifications from what is perceived in the bulk; contrasting, the electrical conductivity exhibited important reductions. The qualitative differences are rationalized in terms of simple geometrical considerations.

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Section: Introductionmentioning

confidence: 99%

Aqueous electrolytes confined within functionalized silica nanopores

Videla

Sala

Martı́

et al. 2011

The Journal of Chemical Physics

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confidence: 99%

“…A few experimental studies have also been conducted; for example, Kittaka et al investigated the phase behavior of water and acetonitrile mixtures in MCM-41 by employing infrared spectra (IR), 16 while Ohkubo et al investigated the hydration structure of metal ions in carbon micropores by extended X-ray absorption fine structure (EXAFS). 17 However, even though their results have shown the importance of understanding multicomponent states in nanometer-order spaces, such experimental approaches are rare.…”

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Small- and Large-angle X-ray Scattering Studies of Nanometer-order Sulfuric Acid Solution in Carbon Micropores

et al. 2012

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The structure of nanometer-order sulfuric acid solution in carbon micropores is investigated by large-and small-angle X-ray scattering experiments. The electron radial distribution function of the nanosolution is different from that of bulk solution. The intermolecular structure of nanosolution does not change with fractional filling. These results and the dependency of density fluctuations of the system with fractional filling showed that the nanometer-order sulfuric acid solutions in carbon micropores form a small molecular assembly with a hydration structure at low fractional filling.In recent times, the rapid progress in nanoscience and nanotechnology 1 has led to the design, development, and application of various new porous materials to many scientific and industrial fields. Furthermore, extensive investigations of the adsorbate behaviors on the surfaces as well in the pores have been ongoing over the last few decades.2,3 The in situ measurements have been performed to examine the structures and behaviors of adsorbed molecules. 48Multicomponent adsorptions, for example, the adsorption of a solution in micropores, are not only of scientific interest but also extremely attractive for many industrial applications. The adsorption of nanometer-order sulfuric acid solution in micropores is important in environmental chemistry 9 and electric double-layer capacitor (EDLC) applications.10 EDLCs are one of the most attractive next-generation energy storage devices because they have high electrical power and can be used almost indefinitely. However, a microscopic understanding of the formation of the electrical double layers in carbon micropores is required for improving the capacitance performance. 10,11 Chmiola et al. 11 and Lin et al. 12 have demonstrated the possibilities of desolvation or distortion of the solvation structures of ions in carbon micropores by electrochemical measurements. These results indicate that the solution structures in carbon micropores could be considerably different from those under bulk conditions.Computer simulations have been employed for investigating nanometer-sized solutions 1315 primarily because of experimental difficulties. A few experimental studies have also been conducted; for example, Kittaka et al. investigated the phase behavior of water and acetonitrile mixtures in MCM-41 by employing infrared spectra (IR), 16 while Ohkubo et al. investigated the hydration structure of metal ions in carbon micropores by extended X-ray absorption fine structure (EXAFS). 17However, even though their results have shown the importance of understanding multicomponent states in nanometer-order spaces, such experimental approaches are rare.X-ray scattering curves directly provide wide-ranging geometric information from intermolecular to colloidal distances; hence, they are indispensable to describe multicomponent adsorption behaviors in nanospaces. In this paper, we describe our investigations into nanosized sulfuric acid solutions in carbon micropores by employing X-ray scattering methods; we...

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“…However, it is well known that some substances are preferentially confined in pores even if they are mixed well in solution. 22,23 We must choose a sample of an ideal solution that does not exhibit such an anomaly.We used a solution of benzene with a slight amount of toluene as a sample, which is a typical case of an ideal solution. The system does not form a solid solution and has a high T fus of benzene, which enables us to observe freezing-point depression.…”

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Freezing-point Depression of Benzene Confined in Mesoporous Silica SBA-15 on Doping with a Slight Amount of Toluene: Ideal Behavior in a Nanometer-sized Space

Ito¹,

Toshiki²,

Tomita³

et al. 2017

Chem. Lett.

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We introduced benzenetoluene solution into the pores of the mesoporous silica material SBA-15 and investigated its fusion behavior using differential scanning calorimetry. On introduction into the pores, the concentration of the solution did not change. The introduced solution exhibited typical behavior of freezing-point depression upon the addition of a toluene component. We discuss this behavior and the large value of the slope of a plot of the fusion temperature of benzene in a confined sample against the logarithm of the molar fraction of benzene. Physical properties of a system confined in a nanometersized space differ from those of the bulk system owing to high interfacial tension and size-limited effects. 120 The physical properties are different from those of the bulk system. Thus, it is not known whether colligative properties, for example, freezingpoint depression or boiling-point elevation, or, in other words, the concept of classical thermodynamic mixing can be applied to such a system confined in a small space. However, it has been reported that this concept is applicable to first-order phase transitions of binary liquid crystals confined within pores. 21 In this study, we examined it in the case of a confined binary system that did not form a solid solution. A binary system that does not form a solid solution displays freezing-point depression when it is in the bulk state.The degree of freezing-point depression caused by doping with a second component is dependent on the entropy of mixing. Thus, the fusion temperature T fus of a solvent decreases linearly with an increase in the chemical potential of the solvent, namely, the logarithm of the reciprocal of the molar fraction of the solvent. The slope of the linear plot is proportional to the reciprocal of the entropy of fusion, ¦ fus S. However, in the case of a system confined in nanometer-sized pores, the ¦ fus S of the system probably differs from that of the bulk system. 1013 In addition, the size of crystals confined in such small pores is very small and we should consider the interfacial effect due to the large interfacial area. Fusion of the solvent in the solution proceeds gradually with an increase in temperature and with a reduction in the size of the crystals of the solvent. This can cause a new phenomenon, which has not been observed in bulk solutions.To investigate the physical behavior of a solution confined in a small pore, we must introduce the solution at any concentration into a pore. However, it is well known that some substances are preferentially confined in pores even if they are mixed well in solution. 22,23 We must choose a sample of an ideal solution that does not exhibit such an anomaly.We used a solution of benzene with a slight amount of toluene as a sample, which is a typical case of an ideal solution. The system does not form a solid solution and has a high T fus of benzene, which enables us to observe freezing-point depression.Firstly, we investigated whether or not this solution could be introduced into a pore at an...

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Phase separation of acetonitrile-water mixtures and minimizing of ice crystallites from there in confinement of MCM-41

Cited by 25 publications

References 17 publications

Aqueous electrolytes confined within functionalized silica nanopores

Aqueous electrolytes confined within functionalized silica nanopores

Small- and Large-angle X-ray Scattering Studies of Nanometer-order Sulfuric Acid Solution in Carbon Micropores

Freezing-point Depression of Benzene Confined in Mesoporous Silica SBA-15 on Doping with a Slight Amount of Toluene: Ideal Behavior in a Nanometer-sized Space

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